Sodium thiosulfate plus sulfuric acid observation. Esters of sulfuric acid
The purpose of the lesson: experimental determination of the factors that affect the rate of a chemical reaction (catalysts, contact area) and chemical equilibrium.
Lesson plan:
Materials and equipment: stand with test tubes, glass rod, diet, water, powder: aluminum, iodine, potassium chloride, solutions: iron (III) chloride, potassium thiocyanate, potassium chloride.
Laboratory workshop
Oprg 1. Effect of a catalyst on the rate of a chemical reaction.
Put a small amount of aluminum powder and finely ground iodine into a dry test tube with a spatula. Mix the contents of the test tube with a glass rod, add a drop of water. How does water affect the rate of a reaction? Based on experiments 1-3, draw a conclusion about the effect of concentration, temperature and catalyst on the rate of chemical reactions.
Experience 2. Shift in chemical equilibrium with a change in the concentrations of reactants.
Pour approximately 1 ml of 0.0025 M solution of iron (III) chloride into a test tube and add the same volume of 0.0025 M solution of potassium thiocyanate. How does the color of the solution change? Divide the resulting solution equally into four test tubes. Keep one tube as a control. Add a few drops of a saturated solution of iron (III) chloride to the second test tube, a few drops of a saturated solution of potassium thiocyanate to the third, and a few crystals of potassium chloride to the fourth. Compare the color of solutions in test tubes. Write an equation for the reversible reaction that occurs. Write a mathematical expression for the chemical equilibrium constant of this process. What substances are in solution in a state of chemical equilibrium? What substance gives the solution a red color? How does the color intensity of the solution change when iron(III) chloride, potassium thiocyanate, potassium chloride are added? In what direction does the equilibrium of the system under study shift in this case? The concentration of which substances and how should be changed in order to shift the chemical equilibrium to the right? Left?
Questions and tasks
1. What is the reason for the change in the reaction rate upon the introduction of a catalyst?
2. What reactions are called reversible? What is the state of chemical equilibrium? What is called the equilibrium constant, on what factors does it depend?
3. What external influences can disturb the chemical balance? In which direction will the equilibrium shift as the temperature changes? Pressure?
Laboratory work № 11
Topic: Basic patterns of chemical reactions.
The purpose of the lesson: To obtain and explore the properties of the most common simple substances and compounds.
Lesson plan:
1. Repeat the main issues of chemical kinetics.
2. On the instructions of the teacher, conduct a laboratory experiment.
Cutlery and utensils: 1) A watch with a second hand or a stopwatch. 2) Measuring cylinder cap. 20 ml.3) Thermometer at 100°. 4) Sealed glass tube with nitrogen dioxide 5) Tripod with clamp and ring. 6) Burner. 7) Chemical beakers cap. 200 ml2 pcs. 8) Asbestos mesh. 9) Rack with test tubes.
Reagents: Potassium chloride KC1.
Solution: 1) Sulfuric acid H 2 S0 4 (1:200). - 2) Sodium sulphate Na2S20 3 (Sh n 1:200).
Laboratory workshop
Experience 1.
The dependence of the reaction rate on the concentration of reactants
a) Add a little H 2 SO 4 to a Na 2 S 2 0 3 solution. Observe the upcoming turbidity of the solution. Turbidity is caused by the interaction of hyposulfite and sulfuric acid, resulting in the release of free sulfur. The reaction goes according to the equation
Na 2 S 2 0 3 + H 2 S0 4 = Na 2 S0 4 + SO 2 + H 3 0 + S
The time that elapses from the start of the reaction to a noticeable clouding of the solution depends on the reaction rate.
b) Pour diluted (1:200) into three large test tubes
Na 2 S 2 O 3 solution in the first - 5 ml, in the second - 10 ml,
in the third - 15 ml. Then add 10 ml of water to the contents of the first test tube and 5 ml of water in the second.
Pour 5 ml of dilute (1:200) sulfuric acid into three other test tubes.
Add 5 ml of H 2 S04 solution with stirring to each test tube with Na 2 S 2 0s and accurately note in the second hand of the clock how many seconds after adding the acid, turbidity is observed in each test tube.
Formulate a conclusion about the dependence of the reaction rate on the concentrations of reactants for a given experiment.
Experience 2. Temperature dependence of the reaction rate
For the experiment, take solutions of Na 2 S 2 0 3 and H 2 S0 4 of the same concentrations as in the previous experiment.
Pour 10 ml of hyposulfite solution into three large test tubes, 10 ml of sulfuric acid into the other three test tubes and divide them into three pairs: a test tube with Na 2 S 2 0 3 and H 2 S0 4 in each pair.
Mark the air temperature in the laboratory and the time on the second hand of the clock, pour together the solutions of the first pair of test tubes and note how many seconds later the turbidity appears.
Place the second pair of test tubes in a beaker with water and heat to a temperature 10° above room temperature. Monitor the temperature with a thermometer dipped into the water. Drain the contents of the tubes and note how many seconds later the turbidity appears.
Repeat the experiment with the third pair of test tubes, heating them in a beaker of water to a temperature 20° above room temperature.
Record the results in the following form:
Draw a graph illustrating the dependence of the reaction rate on temperature for this experience. To do this, on the abscissa axis, plot the temperature of the experiments on a certain scale, and on the ordinate axis, the values reciprocal of the time the turbidity appeared (a unit divided by the number of seconds).
Lab #8
Topic: Solutions. Preparation of solutions of percentage concentration
The purpose of the lesson: to prepare solutions of a given percentage concentration.
Lesson plan:
1. Repeat the main issues of chemical kinetics.
2. On the instructions of the teacher, conduct a laboratory experiment.
Laboratory workshop
Experience 1. Preparation of a 10% solution of sodium chloride weighing 50 g.
Calculate what mass of sodium chloride is required to prepare a 10% solution weighing 50 g. Weigh this mass of salt in a pre-weighed weighing bottle on a technochemical scale with an accuracy of 0.01 g. Calculate the volume of water needed to dissolve the sample taken. Measure this volume of water with a beaker and dissolve the weighed salt in it. Pour the resulting solution into a measuring cylinder and determine the density of the solution with a hydrometer, and then the mass fraction of sodium chloride. Calculate the error of experience
Control questions and tasks.
1. What is a solution? What is a solvent?
2. How can the dissolution process be accelerated? What phenomena accompany dissolution?
3. What are crystalline hydrates and water of crystallization? How is the dependence of the solubility of solids on temperature expressed? How does the solubility of gases change with increasing temperature and pressure?
4. What is called the concentration of the solution? What solutions are called molar, normal?
Lab #9
Topic: Preparation of solutions of molar and normal concentration.
The purpose of the lesson: to prepare solutions of a given molar and normal concentration.
Lesson plan:
1. Repeat the main issues of chemical kinetics.
2. On the instructions of the teacher, conduct a laboratory experiment.
Materials and equipment: a set of hydrometers, a 500 ml measuring cylinder, crist: sodium chloride, barium chloride crystalline hydrate, solutions: sulfuric acid, hydrochloric acid.
Laboratory workshop
2.1. The purpose of the work: to determine the influence of various factors on the rate of a chemical reaction, to get acquainted with the methods for determining the average rate constant, reaction order, activation energy.
2.2. Objects and means of research: 0.1M solutions of sodium thiosulfate and sulfuric acid, distilled water, test tubes, two burettes, 2 ml pipette, thermostat, stopwatch.
2.3. Program of work
2.3.1. Effect of Concentration on Reaction Rate .
As a result of the reaction between sulfuric acid and sodium thiosulfate, sulfur is formed, which is released in the form of turbidity. The time from the start of the reaction to the moment of turbidity (bluish opalescence) depends on the reaction rate. This makes it possible to judge the average reaction rate.
The reaction proceeds in three stages:
1) Na 2 S 2 O 3 + H 2 SO 4 = Na 2 SO 4 + H 2 S 2 O 3
2) H 2 S 2 O 3 \u003d H 2 SO 3 + S¯
3) H 2 SO 3 \u003d H 2 O + SO 2
Summary Equation:
Na 2 S 2 O 3 + H 2 SO 4 = Na 2 SO 4 + SO 2 + S¯ + H 2 O
The slowest, rate-determining, stage is the second, therefore, the rate of the whole process depends only on the concentration of thiosulfuric acid. Since thiosulfuric acid is obtained as a result of an ion exchange reaction that occurs almost instantly, we can assume that the concentration of thiosulfuric acid is equal to the concentration of sodium thiosulfate and the rate of the entire process depends on the concentration of sodium thiosulfate.
Progress.
Prepare four solutions of sodium thiosulfate of different concentrations according to Table 3. Add 2 ml of 0.1M sulfuric acid solution to each solution in turn and measure the time from the moment the acid is added to the moment cloudiness appears. Record the results in table 3, given that ΔС is a constant value equal to 4×10 -3 mol/l.
Table 3
Based on the data obtained, construct a graph lgV \u003d f (lgC) to determine the order of the reaction at a temperature T 1 (K). Graphs are built manually on graph paper in the appropriate scale or in Microsoft Excel 2007.
To build graphs in Microsoft Excel 2007, you need to enter the source data into a spreadsheet.
Then you need to select the range of cells A2:B5 with data and select from the menu Insert - Charts - Scatter and, having selected the obtained points on the chart, select in the context menu Add Trendline - Linear - Show Equation on Chart x) and is n - the order of the reaction. For example, n = 0.9919 ≈ 1
To determine the reaction rate constant k 1 at room temperature, plot the dependence V = f(C) either manually or using Microsoft Excel 2007.
To plot graphs in Microsoft Excel 2007, enter the initial data into a spreadsheet. Note that for the speed column ( V) must be chosen exponential cell format . As a result, we obtain a graph of a straight-line dependence, in the equation of which the multiplier for the independent variable ( x) is the rate constant of the reaction.
For example, k = 1.6 10 -3
2.3.2. Effect of temperature on the reaction rate.
The experiment is carried out similarly to the previous one. However, solutions of sodium thiosulfate and sulfuric acid must be preheated in a thermostat for 5 minutes before mixing.
Record the results in table 3 (T 2).
Based on the results of calculations and measurements, plot V \u003d f (C) and determine the reaction rate constant k 2 at elevated temperature (T 2), also using the capabilities of Microsoft Excel 2007. Find the temperature coefficient of the reaction rate:
Based on the experimental data 3.1.1. and 3.1.2. calculate the activation energy of the reaction E act. according to the formula:
where R = 8.31 J/(mol K) is the universal gas constant;
T 1 and T 2 -temperature, K;
k 1 and k 2 - reaction rate constants at temperatures T 1 and T 2 , respectively, with -1 .
End of work -
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Chemical vessels
1.1. Purpose of work: To study the types and purpose of chemical glassware. 1.2. Theoretical information Chemical glassware used in laboratories can be divided into several
Measuring chemical glassware and methods of working with it
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Scales and weighing rules
1.1. Purpose of the work: To get acquainted with weighing devices. Learn to weigh on laboratory scales. 1.2. Theoretical information. To determine m
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Topic: RATE OF CHEMICAL REACTIONS AND
CHEMICAL EQUILIBRIUM
Temperature dependence of the reaction rate
(checking the van't Hoff rule)
The regularity is studied on the example of the interaction of sodium thiosulfate with sulfuric acid
The reaction proceeds in two stages:
The first stage - ion exchange - occurs instantly, so that in fact the monitoring is carried out over the rate of the second monomolecular stage, a sign of the course of which is the appearance of turbidity as a result of the formation of elemental sulfur. Therefore, the concentration of sulfuric acid does not actually affect the rate of the reaction, as long as it is taken in an amount sufficient for the complete interaction of thiosulfate, and is the same in all experiments.
Therefore, the velocity equation can be written as:
Experience 1. Prepare a simple thermostat: a 200 ml glass with a lid that has 3 holes. Insert a thermometer fixed on a thread into the first hole, into the second - a conical test tube with a -2 N solution of H 2 SO 4 with a pipette lowered into it, into the third - a conical test tube, into which 10 drops of 0.1-N sodium thiosulfate solution are added with a clean pipette. Fill the glass with water aged at room temperature so that the bulb of the thermometer and the solution are immersed in it. The mercury ball of the thermometer and the solutions of the reactants should be at the same level in the middle part of the water filling the glass - the thermostat.
After waiting 5 minutes - the time required to equalize the temperature of the water in the thermostat and the solutions in the test tubes, record the thermometer readings. Without removing the test tubes from the thermostat, add 1 drop of sulfuric acid solution to the sodium thiosulfate solution with a pipette. At this moment, turn on the stopwatch (measure the time on a clock with a second hand), without removing the test tube from the thermostat, observe the course of the experiment until a cloudiness that is noticeable to the eye appears in the test tube and, if it is detected, turn off the stopwatch. Record the duration of the experiment in seconds.
Experience 2. It is carried out at a temperature increased by 10 °. To do this, replace the test tube in the thermostat in which the experiment was carried out with a clean one and add 10 drops of 0.1 N sodium thiosulfate solution into it again. Adding hot water to the glass, raise its temperature by 14 - 15 ° above the temperature of the first experiment and observe its cooling with a thermometer. When the temperature is 10° higher, carry out the experiment in exactly the same way as the first.
Experience 3. Carrying out the experiment at a temperature increased by 20 °. The experiment is carried out in the same way as in the previous case, but the temperature of the water in the thermostat initially rises by 24 - 25 ° above room temperature, and the addition of sulfuric acid to hyposulfite is carried out at the moment when it is exactly 20 ° above the temperature of the first experiment. All experimental data and calculation results are recorded in the form of a table. Instead of indices, indicate the actual temperatures.
Calculate:
A) the relative rate of the reaction.
Let's take the reaction rate at room temperature
in the first experience. Since the speed and magnitude, the reciprocal of time,
from this proportion we find
Similarly, we make a proportion and calculate
B) thermal velocity coefficient according to van't Hoff. It is calculated from the results of two experiments, independently of one another.
The performance of the work is satisfactory if the results of these two calculations differ slightly. Then you can take their average values. In case of a sharp discrepancy, the work must be repeated.
The rate of chemical reactions in homogeneous and
HETEROGENEOUS SYSTEMS
Experience 1. The influence of the size of the interface of reactants on the reaction rate in a heterogeneous system
Dissolution of calcium carbonate in hydrochloric acid
Completing of the work. Take two small, if possible identical, pieces of chalk. Put one of them on a piece of filter paper and grind it into powder with a glass rod. Place the resulting powder into a conical test tube. The second piece of chalk is completely lowered into another conical test tube. In both test tubes simultaneously add the same amount (10-20 drops) of hydrochloric acid with a density of 1.19 g/cm 3 . (To maintain the simultaneous addition of acid, the experiment can be carried out by two students together). Note the time of complete dissolution of the chalk in each case.
Recording experience data. Write the equation for the corresponding
reactions. Why is the dissolution rate of chalk in these two cases
different?
Experience 2. The effect of a catalyst on the reaction rate
Catalytic reduction of iron (III) Performance of work. Add 10 drops of 0.5 N to two test tubes. potassium thiocyanate solution and 1 drop of 0.5 n. solution...Experience 3. Shifting the chemical equilibrium of reversible reactions
Influence of the concentration of reacting substances on the equilibrium shift Performance of work. Add 5-7 drops of 0.0025 N to four conical tubes. solutions of iron chloride (III) and ...TOPIC: SOLUTIONS
Experience 1 Determination of the density of the solution with a hydrometer.
Figure 1 - Hydrometer for determining the density of the solutionExperience 2 Preparation of solutions of various concentrations
A) Preparation of a 0.1N solution of sulfuric acid.
2. How many ml of a 10% sulfuric acid solution (ρ, see experiment No. 1) must be taken to prepare 250 ml of a 0.1N sulfuric acid solution. 3. How many ml of a 15% sulfuric acid solution (ρ, see experiment No. 1) is necessary ... 4. How many ml of a 15% sulfuric acid solution (ρ, see experiment No. 1) must be taken to prepare 250 ml of a 0.1 n solution ...B) Preparation of a solution of a given concentration by mixing solutions of a higher and lower concentration
2. Prepare 150 ml of 12% sodium hydroxide solution, having at your disposal 5% and 25% NaOH solutions. 3. Prepare 500 ml of 20% sodium hydroxide solution, having in your own, ... 4. Prepare 250 ml of 15% sodium hydroxide solution, having in your disposal 8% and 25% solutions ...Experience 3 Determination of the concentration of solutions
Rinse a burette with a capacity of 10 ml (Figure 2c) with a small volume of 0.1 N NaOH solution, then pour it through the lower end of the burette, equipped with ... Add a dry pipette to a conical flask with a capacity of 30-50 ml (Figure 2b) ... Repeat the titration three more times. A sharp change in the color of phenolphthalein from one drop of alkali is an indicator ...TOPIC: THE THEORY OF ELECTROLYTIC DISSOCIATION
Experience 1. Comparison of the electrical conductivity of solutions of some electrolytes.
Pour 20-30 ml of distilled water into a glass with electrodes. Does the lamp light up? Does water conduct electricity? Add 4-5 to a glass of water ... Explain why a salt solution is a current conductor, although pure water and ... Pour 20-30 ml of 0.1 n into four glasses with a capacity of 50 ml each. solutions: in the first - hydrochloric acid, in ...Experience 2. The nature of the dissociation of hydroxides
Completing of the work. Number 5 tubes and add 4-5 drops of 0.5 N. solutions: in the first test tube MgCl2, in the second - AlCl3, in the third ... Similarly, investigate the properties of hydroxides of aluminum, silicon, nickel (II) and zinc. What do they dissolve into?Experience 3. Comparison of the chemical activity of acids
a) Interaction of hydrochloric and acetic acids with marble. Performance of work. Introduce 3-4 drops of 2n into one test tube. acetic acid solution, in another - the same amount of 2 n. solution...Experience 4. Shifting the equilibrium of dissociation of weak electrolytes
a) Influence of a salt of weak acids on the dissociation of this acid Performance of work. In two test tubes, 5-7 drops of 0.1 N. acetic acid solution. Add one to each tube...Experience 1. The reaction of the medium in solutions of various salts
Stir the solutions (do not transfer glass rods from one solution to another). By changing the color of litmus, draw a conclusion about the reaction of the medium in a solution of each ... Which of the studied salts undergo hydrolysis? Write the ionic and molecular equations for the reactions of their hydrolysis and ...Experience 2. Formation of basic and acidic salts during hydrolysis
A) Hydrolysis of sodium sulfite
The presence of which ions in the solution is indicated by the found pH value? As a result of what process did these ions appear? By the absence of the smell of sulfur dioxide, make sure that sodium sulfite ... Write the molecular and ionic equations for the hydrolysis of sodium sulfite. Which salts are hydrolyzed to produce...Experience 3. Factors affecting the degree of hydrolysis of salts
A) The effect of the strength of an acid and a base forming a salt on the degree of its hydrolysis
Write the ionic equations for the hydrolysis of sodium sulfite and sodium carbonate (in the first stage). In a solution of which salt, the color of phenolphthalein is more ... The degree of hydrolysis of which salt at the same concentrations and temperatures should ... Make a general conclusion about the effect of the strength of the acid and base that form the salt on the degree of its hydrolysis.TOPIC: REDOX
PROCESSES
HYDROGEN
Experience 1 Obtaining hydrogen
Open the valve of the gas outlet pipe. Watch how the acid pours into the apparatus, fills its lower part and rises to the middle, where it is ... Familiarize yourself with the automaticity of the operation of the Kipp apparatus. To do this, turn off the tap... NEVER ignite the hydrogen at the end of the Kipp's gas outlet tube without checking it for cleanliness and without being...HYDROGEN PURITY CHECK
Experience 2 Transfusion of hydrogen.
Check the purity of hydrogen and fill a large test tube with it, holding it upside down, place next to it, also upside down, another test tube so that their holes are next to each other. Without moving the test tubes with hydrogen, turn it upside down so that the empty test tube covers the test tube with hydrogen. After separating the test tubes, bring each of them to the flame of an alcohol lamp. In which test tube is the outbreak observed?
Experience 3 Formation of water during combustion.
CHECK HYDROGEN for purity. If it is clean, light it at the end of the gas tube and, holding the tube up, cover the flame with a glass jar, stopping the process of hydrogen evolution. What needs to be done for this? What is observed on the walls of the bank? Write down the reaction equation.
OXYGEN
OBTAINING OXYGEN AND BURNING SUBSTANCES IN IT
1. Familiarize yourself with the device of the gasometer. 2. Place potassium permanganate in a test tube, close with a stopper with a gas outlet ...Experience 2. Combustion of sulfur in oxygen.
Experience 3. Combustion of magnesium in oxygen.
Fill the jar with oxygen, as in the previous experiment. Take shavings or a ribbon of magnesium with crucible tongs, heat it in the flame of an alcohol lamp until it lights up and quickly add it to a jar of oxygen. What is magnesium oxide? Test the nature of magnesium oxide. To do this, as in the previous experiment, pour a little solution of purple litmus into the jar and shake. How did the color of the litmus change? Make a conclusion about the nature of the resulting hydroxide.
Experience 4. Combustion of iron in oxygen.
The influence of the medium on the course of redox processes The influence of the pH of the medium on the nature of the reduction of potassium permanganateH2O2 + 2H+ + 2e- = 2H2O
for the oxidation reaction of hydrogen peroxide (H 2 O 2 - reducing agent):
H 2 O 2 - 2e - \u003d O 2 + 2H +
b) Interaction of hydrogen peroxide with potassium iodide
Completing of the work. To a solution of potassium iodide, acidified with sulfuric acid, add 1 - 2 drops of a solution of hydrogen peroxide. For what type of substance did the color of the solution appear?
Write the reaction equation. Is hydrogen peroxide an oxidizing or reducing agent?
c) Interaction of hydrogen peroxide with mercury oxide (II)
Completing of the work. Place 3-4 drops of mercury nitrate solution in a test tube Hg(NO 3) 2 and add the same amount of 2 n. alkali solution until precipitation of mercury oxide (II). Note the color of the precipitate. Add 4 - 5 drops of hydrogen peroxide solution and observe the color change of the precipitate due to the formation of suspended particles of metallic mercury. What gas is released?
Write the reaction equation. Is hydrogen peroxide the oxidizing and reducing agent in this reaction? Draw appropriate conclusions.
DETERMINATION OF ELECTRODE POTENTIALS. DIRECTION
REDOX
PROCESSES
Performing the work. Fill one of the microcups 1 (figure) to the top with a 1M solution of zinc sulfate (more precisely, a solution in which the activity of ions ... Record the data of the experiment. Depict a double electric layer at the interface between the metal - a solution of its salt on zinc and ...ELECTROLYSIS OF AQUEOUS SOLUTIONS
The experiments described below are carried out in the apparatus shown in the figure.B) Electrolysis of potassium iodide solution
Note the color change of the solution near the cathode and anode. Write the equation of the cathode and anode processes. Why did the solutions in the cathode and ...C) Electrolysis of sodium sulfate solution
Completing of the work. In a beaker with a volume of 100 ml, mix a solution of sodium sulfate with a neutral solution of litmus and pour the resulting solution into ...D) Electrolysis of aqueous solutions of salts with soluble anodes
Completing of the work. Pour into the electrolyzer 0.5 N. copper sulfate solution, lower the graphite electrodes into it and pass an electric current through the solution. After a few minutes, stop the electrolysis and mark the red copper coating on the cathode. Write the equations of the cathode and anode processes. What gas is released in small quantities at the anode?
Without disconnecting the electrolyzer from the battery, swap the electrodes in the knees of the electrolyzer, as a result of which the electrode, which was first covered with copper, will turn out to be the anode. Pass the electric current again. What happens to the copper at the anode? What substance is released at the cathode? Write the equations of the cathodic and anode processes occurring during the electrolysis of copper sulfate with a copper anode.
Carry out a similar experiment with 0.5 n. nickel(II) sulfate solution. What is released at the cathode? Write an equation for the cathodic reduction of nickel. What substance is oxidized at the anode during the electrolysis of nickel sulfate with a carbon anode? With a nickel anode? Write the equations of the corresponding anodic processes.
TOPIC: COMPLEX COMPOUNDS
Experience 1. Obtaining and properties of some ammonias
Dilute the solution with an approximately equal volume of alcohol and centrifuge the resulting crystals of [Сu(NH3)4]SO4 ·H2O - complex ... Write the equations of all reactions carried out in this experiment.Experience 2. Study of tetraamine cupro (׀׀) sulfate
Pipette 10 drops of the test solution of the complex salt into four numbered test tubes. a) Test for the Cu2+ ion by the action of alkali. Add a few drops to test tube No. 1 ... b) Test for Cu2+ ion by the action of sodium sulfide. Add a few drops of Na2S solution to test tube No. 2. Is it observed...TOPIC: CHEMISTRY OF THE ELEMENTS
HALOGENS
Experience 1. Obtaining chlorine
Completing of the work. Put 3-4 crystals of various oxidizing agents into three test tubes: in the first, manganese dioxide MnO2 or lead dioxide PbO2, in ... a) obtaining chlorine, given that the oxidation numbers of manganese change from +4 to ... b) the interaction of chlorine with sodium thiosulfate with the participation water; the reaction proceeds with the formation of free sulfur, ...Experiment 2. Obtaining chlorine water and studying its properties
A) Obtaining chlorine water
Write the reaction equation for the production of chlorine by oxidation of hydrochloric acid with potassium permanganate, given that the oxidation number of manganese varies from ...B) Study of the composition and properties of chlorine water
Cl2 + H2O ↔HClO + HCl. (1) In this case, the equilibrium is strongly shifted to the left. Therefore, chlorine water can be ... HClO \u003d HCl + O (2)Experience 3. Obtaining bromine
Completing of the work. Place 2-3 crystals of potassium or sodium bromide and the same amount of manganese dioxide into a dry cylindrical test tube. Gently shake the test tube and add 2-3 drops of concentrated sulfuric acid (pl. 1.84 g/cm3) to the mixture. What are the prominent brown vapors? Write the reaction equation for the production of bromine.
Experience 4. Obtaining iodine
Experiment 5. Oxidizing properties of free halogens (oxidizing number is ...A) Comparison of the oxidative activity of free halogens.
By the color of the benzene ring, determine which halogen is released in the free state in each case. Write the equations for the reactions of mutual ...B) Oxidation of magnesium or zinc with bromine.
Contribute in a test tube 3 - 5 drops of bromine water and a little powder of magnesium or zinc. Stir with a glass rod. Note the discoloration of solutions with bromine water and indicate the cause of this phenomenon. Write the corresponding reaction equation.
Experiment 6. Obtaining hydrogen compounds of halogens (hydrogen halides).
Hydrogen halides can be produced by the action of non-volatile and non-oxidizing acids on metal halides.
B) The action of hydrofluoric acid on glass.
C) Obtaining hydrogen chloride and its dissolution in water.
After filling the test tube with hydrogen sulfide, close it tightly with a stopper. Disconnect the capillary from the tube, quickly close it with your index finger and, turning it over ...D) Production of hydrogen bromide and hydrogen iodide.
Put 2-3 microspatulas of cadium or sodium bromide into one test tube, and the same amount of any iodide into another. Add 5-10 drops of a concentrated solution of orthophosphoric acid to both tubes. Heat the solutions on a small burner flame. Observe the evolution of hydrogen bromide and hydrogen iodide in the form of white smoke. Does this release free bromine and iodine? To conclude, does phosphoric acid oxidize hydrogen bromide and hydrogen iodide? Write reaction equations.
Experience 7. Reducing properties of hydrogen halides and halide ions.
A) Recovery of sulfuric acid.
Note in the second test tube the release of brown vapors of bromine and sulfur dioxide SO2, in the third - violet vapors of iodine, sulfur and hydrogen sulfide formed ... Write the reaction equation for the interaction of chloride, bromide and potassium iodide or ...B) Recovery of iron trichloride.
Can negative halogen ions be oxidizing agents? Justify the answer. Experience 8. Interaction of bromine with aluminum. Pour bromine into a demonstration tube fixed in a rack over a tray with sand. Drop an aluminum...Experience 1. Obtaining ammonia and studying its properties
Experience 2. Obtaining oxides of nitrogen and nitric acid
a) obtaining nitric oxide (II) by the interaction of dilute nitric acid with copper; b) oxidation of nitric oxide (II) to nitric oxide (IV) and oxide polymerization ... c) interaction of nitrogen dioxide with water, proceeding with the formation of nitric and nitrous acids;Experience 3. Obtaining nitrous acid and its decay
a) interaction of potassium nitrite with sulfuric acid; b) decomposition of nitrous acid; c) decomposition of nitrous anhydride.Experience 4. Redox properties of nitrites
1. Add 2-4 drops of potassium iodide solution and the same amount of 2N sulfuric acid to the test tube. Add 2-4 drops of potassium or sodium nitrite solution. Than… 2. Interaction of potassium nitrite with permanganate. Add 2-3 drops to the test tube...Experience 5. Oxidizing properties of nitric acid
Reaction of dilute nitric acid with copper and tin
2. Interaction with concentrated nitric acid with copper and tin. Place a small piece of copper and tin into 2 test tubes. Add them to...Experience 6 . Salts of nitric acid
Place 2-3 microspatulas of dry potassium nitrate into a cylindrical tube. Having strengthened it obliquely in a tripod, heat until the salt melts. Contribute…Experience 1. Allotropy of phosphorus
P+CuSO4+H2O H3PO4+H2SO4+CuExperience 2. Salts of orthophosphoric acid
Find the dissociation constants of orthophosphoric acid and determine whether alkali metal orthophosphates undergo hydrolysis. Check your…SULFUR AND ITS PROPERTIES
Experience 1. Sulfur allotropy
1. Obtaining plastic sulfur. In a 10 ml test tube. pour on ¼ of the volume of small pieces of cutting sulfur. Fix the test tube in the holder and…Experience 2. Obtaining sulfur dioxide and sulfurous acid
Fill the micro flask to 1/3 of its volume with sodium sulfate crystals, add 6-8 drops of 4 and sulfuric acid solution and quickly close with a stopper about ... Experiment 3. Oxidizing and reducing properties of sulfur (IV)Experience 5. Dehydrating properties of sulfuric acid
Experience 6 Theosulfuric acid and theosulfates
1. Study of thiosulfuric acid. Add 5-6 drops of sodium thiosulfate Na2S2O3 solution and 3-4 drops of sulfuric acid solution to the test tube. Note… 2. Interaction of sodium thiosulfate with chlorine and bromine. In two test tubes with… 3. Interaction of sodium thiosulfate with iodine. In a test tube with iodine water (5-6 drops), add dropwise a solution ...APPENDIX
Table 1 - Instability constants of some complex ions
| complex ion | K nest |
| - | 1 ∙ 10 -21 |
| + | 7 ∙ 10 -8 |
| 3- | 1 ∙ 10 -13 |
| 2- | 9 ∙ 10 -3 |
| 2- | 8 ∙ 10 -7 |
| 2- | 1 ∙ 10 -17 |
| 2+ | 8 ∙ 10 -8 |
| 2+ | 8 ∙ 10 -6 |
| 3+ | 6 ∙ 10 -36 |
| 2+ | 2 ∙ 10 -13 |
| 3- | 5 ∙ 10 -28 |
| 4- | 1 ∙ 10 -37 |
| 3- | 1 ∙ 10 -44 |
| 2+ | 1 ∙ 10 -3 |
| 2- | 1 ∙ 10 -21 |
| 2- | 8 ∙ 10 -16 |
| 2- | 1 ∙ 10 -30 |
| 2- | 1 ∙ 10 -22 |
| 2- | 3 ∙ 10 -16 |
| 2+ | 2 ∙ 10 -9 |
| 2- | 2 ∙ 10 -17 |
| ] 2+ | 4 ∙ 10 -10 |
Table 2 - Density of solutions of some acids, alkalis and ammonia at 20 0 C (in g / cm 3, g / ml).
Problem 866.
Write the reaction equation for obtaining sodium thiosulfate. What is the oxidation state of sulfur in this compound? Does thiosulfate ion exhibit oxidizing or reducing properties? Give examples of reactions.
Solution:
Production reaction equations sodium thiosulfate:
a) An aqueous solution of sodium sulfite is boiled in the presence of sulfur, and then cooled, a crystalline hydrate is released sodium thiosulfate:
Na 2 SO 3 + S + 5H 2 O ↔ Na 2 S 2 O 3 . 5H2O.
An aqueous solution of sodium sulfite is boiled in the presence of sulfur, and then cooled, sodium thiosulfate crystalline hydrate is released.
b) Oxidation of polysulfides with atmospheric oxygen:
2Na 2 S 5 + 3O 2 ↔ 2Na 2 S 2 O 3 + 6S.
c) Obtaining sodium thiosulfate by reacting sulfur with alkali. The reaction proceeds with simultaneous oxidation and reduction of sulfur:
4S + 6NaOH ↔ Na 2 S 2 O 3 + 2Na 2 S + 3H 2 O.
d) Direct interaction of sulfur dioxide with hydrogen sulfide in an alkaline environment. To do this, a mixture of both gases is passed with strong stirring into a solution of caustic soda until it is neutralized, then sodium thiosulfate is formed:
4SO 2 + 2H 2 S + 6NaOH ↔ 3Na 2 S 2 O 3 + 5H 2
The sulfur atoms that make up the thiosulfates have different degrees of oxidation; at one atom, the degree of oxidation is +4, at the other 0. The thiosulfate ion S 2 O 3 2- exhibits the properties of a reducing agent. Chlorine, bromine and other strong oxidizing agents oxidize it to the sulfate ion SO 4 2-, for example:
Interaction sodium thiosulfate with chlorine (with its excess):
Na 2 S 2 O 3 + 4Cl 2 + 5H 2 O ↔ 2H 2 SO 4 + 2NaCl + 6HCl
Ionic-molecular equation:
S2O 3 2- + 4Cl 2 0 + 5H 2 O ↔ 2SO 4 2- + 8Cl - +10H+
Molecular Form:
Na 2 S 2 O 3 + 4Cl 2 + 5H 2 O ↔ 2H 2 SO 4 + 2NaCl + 6HCl l
In this reaction, sodium thiosulfate acts as a reducing agent, increasing the oxidation state of one sulfur atom from 0 to +4, the other from +4 to +6.
Under the action of a weak oxidizing agent, sodium thiosulfate is oxidized to salt tetrathionic acid H 2 S 4 O 6 .
Interaction of sodium thiosulfate with iodine:
2 Na 2 S 2 O 3 + I 2 ↔ Na 2 S 4 O 6 + 2NaI
Ion-molecular balance equations:
Ionic-molecular equation:
2S 2 O 3 2- + I 2 0 ↔ S 4 O 6 2- + 2I -
Molecular Form:
2Na 2 S 2 O 3 + I 2 ↔ Na 2 S 4 O 6 + 2NaI
In this reaction, sodium thiosulfate acts as a reducing agent, increasing the oxidation state of one sulfur atom from 0 to +4. When heated above 200 0C, sodium thiosulfate decomposes according to the scheme:
4Na 2 S 2 O 3Na 2 SO 4 + Na 2 S + 4S↓
In this case, the autoxidation-reduction reaction takes place.
Sulfuric acid reactions
Problem 867.
Compose reaction equations: a) concentrated H 2 SO 4 with magnesium and silver; b) dilute H 2 SO 4 with iron.
Solution:
a) 4Mg + 5H 2 SO 4 (conc.) → 4MgSO 4 + H 2 S) + 4H 2 O;
b) 2Ag + 2H 2 SO (conc.) → Ag 2 SO 4 + SO 2 + 2H 2 O;
c) Fe + H 2 SO 4 (diff.) → FeSO 4 + H 2.
Problem 868.
How many grams of sulfuric acid is needed to dissolve 50 grams of mercury? How many of them will go to oxidize mercury? Can dilute sulfuric acid be used to dissolve mercury?
Solution:
Reaction equation:
Ion-molecular balance equations:
Ionic-molecular equation:
Hg + SO 4 2- + 4H + ↔ Hg 2+ + SO 2 + 2H 2 O
It follows from the oxidation-reduction equations that 1 mol of H2SO4 is spent on the oxidation of 1 mol of Hg, therefore,
200,5: 98 = 50: X; X = (98 . 50) / 200.5 \u003d 24.44 g.
We find the mass of H2SO4 from the proportion:
200,5: (2 . 98) = 50: X; X = (2 . 98 . 50) / 200.5 \u003d 48.88 g.
Answer: 48.88 g; 24.44 g. Mercury is in the series of voltages after hydrogen - therefore, dilute sulfuric acid does not act on mercury. Therefore, to dissolve mercury, you need to take concentrated sulfuric acid.
Problem 869.
Is the same amount of sulfuric acid required to dissolve 40 g of nickel, if in one case we take a concentrated acid, and in the other a dilute one? What mass of sulfuric acid will be used to oxidize nickel in each case?
Solution:
Reaction equations:
a) Ni + 2H 2 SO 4 (conc.) → NiSO4 + SO2 + 2H2O;
b) Ni + H 2 SO 4 (diff.) → NiSO4 + H2.
We calculate the mass of concentrated sulfuric acid used for the oxidation of 40 g of nickel from the proportion:
58,7: (2 . 98) = 40:X; X = (2 . 98 . 40) / 58.7 \u003d 133.56, g.
Now we calculate the mass of dilute sulfuric acid used for the oxidation of 40 g of nickel from the proportion:
58,7: 98 = 40: X; X = (98 . 40) / 58.7 \u003d 66.78 g.
Answer: 133.56 g; 66.78 g. The same amount of sulfuric acid is consumed for the oxidation of nickel.
Thiosulfuric acid. sodium thiosulfate. Obtaining, properties, application.
Sulfuric acid esters include dialkyl sulfates (RO2)SO2. These are high-boiling liquids; the lower ones are soluble in water; in the presence of alkalis, they form alcohol and salts of sulfuric acid. Lower dialkyl sulfates are alkylating agents.
Diethyl sulfate (C2H5)2SO4. Melting point -26°C, boiling point 210°C, soluble in alcohols, insoluble in water. Obtained by the interaction of sulfuric acid with ethanol. It is an ethylating agent in organic synthesis. Penetrates through the skin.
Dimethyl sulfate (CH3)2SO4. Melting point -26.8°C, boiling point 188.5°C. Let's dissolve in alcohols, it is bad - in water. Reacts with ammonia in the absence of a solvent (explosively); sulfonates some aromatic compounds, such as phenol esters. Obtained by interaction of 60% oleum with methanol at 150°C. It is a methylating agent in organic synthesis. Carcinogen, affects the eyes, skin, respiratory organs.
Sodium thiosulfate Na2S2O3
Salt of thiosulfuric acid, in which two sulfur atoms have different oxidation states: +6 and -2. Crystalline substance, highly soluble in water. It is produced in the form of Na2S2O3 5H2O crystalline hydrate, commonly called hyposulfite. Obtained by the interaction of sodium sulfite with sulfur during boiling:
Na2SO3+S=Na2S2O3
Like thiosulfuric acid, it is a strong reducing agent. It is easily oxidized by chlorine to sulfuric acid:
Na2S2O3+4Сl2+5Н2О=2H2SO4+2NaCl+6НCl
The use of sodium thiosulfate to absorb chlorine (in the first gas masks) was based on this reaction.
Sodium thiosulfate is oxidized somewhat differently by weak oxidizing agents. In this case, salts of tetrathionic acid are formed, for example:
2Na2S2O3+I2=Na2S4O6+2NaI
Sodium thiosulfate is a by-product in the production of NaHSO3, sulfur dyes, in the purification of industrial gases from sulfur. It is used to remove traces of chlorine after bleaching fabrics, to extract silver from ores; is a fixer in photography, a reagent in iodometry, an antidote for poisoning with arsenic, mercury compounds, an anti-inflammatory agent.
Thiosulfuric acid- an inorganic compound, a dibasic strong acid with the formula H 2 SO 3 S. A colorless viscous liquid that reacts with water. Forms salts - inorganic thiosulfates. Thiosulfuric acid contains two sulfur atoms, one of which has an oxidation state of +4, and the second is electrically neutral.
Receipt
The reaction of hydrogen sulfide and sulfur trioxide in ethyl ether at low temperatures:
The action of gaseous hydrogen chloride on sodium thiosulfate:
Physical properties
Thiosulfuric acid forms a colorless viscous liquid that does not freeze even at very low temperatures. Thermally unstable - decomposes already at room temperature.
Quickly, but not instantly, decomposes in aqueous solutions. In the presence of sulfuric acid, it decomposes instantly.
Chemical properties
Thermally very unstable:
Decomposes in the presence of sulfuric acid:
Reacts with alkalis:
Reacts with halogens:
Forms esters - organic thiosulfates.
Sodium thiosulfate (antichlor, hyposulfite, sodium sulfidotrioxosulfate) - Na 2 S 2 O 3 or Na 2 SO 3 S, a salt of sodium and thiosulfuric acid, forms a crystalline Na 2 S 2 O 3 5H 2 O.
Receipt
Oxidation of Na polysulfides;
Boiling excess sulfur with Na 2 SO 3:
The interaction of H 2 S and SO 2 with NaOH (a by-product in the production of NaHSO 3, sulfur dyes, in the purification of industrial gases from S):
Boiling excess sulfur with sodium hydroxide:
then, according to the above reaction, sodium sulfide adds sulfur, forming sodium thiosulfate.
At the same time, during this reaction, sodium polysulfides are formed (they give the solution a yellow color). For their destruction, SO 2 is passed into the solution.
Pure anhydrous sodium thiosulfate can be obtained by reacting sulfur with sodium nitrite in formamide. This reaction proceeds quantitatively (at 80 °C in 30 minutes) according to the equation:
Dissolution of sodium sulfide in water in the presence of atmospheric oxygen:
Physical and chemical properties
Colorless monoclinic crystals. Molar mass 248.17 g/mol (pentahydrate).
Soluble in water (41.2% at 20°C, 69.86% at 80°C).
At 48.5 °C, the crystalline hydrate dissolves in its water of crystallization, forming a supersaturated solution; dehydrated at about 100°C.
When heated to 220 ° C, it decomposes according to the scheme:
Sodium thiosulfate is a strong reducing agent:
With strong oxidizing agents, such as free chlorine, it oxidizes to sulfates or sulfuric acid:
Weaker or slower acting oxidizing agents, for example, iodine, are converted into salts of tetrathionic acid:
The above reaction is very important, as it serves as the basis of iodometry. It should be noted that in an alkaline medium, sodium thiosulfate can be oxidized with iodine to sulfate.
It is impossible to isolate thiosulfuric acid (hydrogen thiosulfate) by the reaction of sodium thiosulfate with a strong acid, since it is unstable and immediately decomposes:
Molten hydrated Na 2 S 2 O 3 ·5H 2 O is very prone to supercooling.
Application
for removing traces of chlorine after bleaching fabrics
for the extraction of silver from ores;
fixer in photography;
Reagent in iodometry
antidote for poisoning: As, Br, Hg and other heavy metals, cyanides (translates them into thiocyanates), etc.
for intestinal disinfection;
for the treatment of scabies (together with hydrochloric acid);
Anti-inflammatory and anti-burn agent;
can be used as a medium for determining molecular weights by freezing point depression (cryoscopic constant 4.26°)
Registered in the food industry as a food additive E539.
admixtures for concrete.
for cleansing tissues from iodine
· Gauze bandages impregnated with sodium thiosulfate solution were used to protect the respiratory organs from the poisonous substance chlorine during the First World War.
