Question

To study the effect of concentration of sodium thysulphate sol. On the rate of reaction between sodium thiosulphate and hydrochloric acid

Answer 1

To Study the Effect of Concentration on the Rate of Reaction Between Sodium Thiosulphate and Hydrochloric Acid

Theory

According to the law of mass action, rate of a chemical reaction is directly proportional to the product of the molar concentrations of the reactants. In other words, the rate of reaction increases with the increase in the concentration of the reactants. The effect of concentration of reactants on rate of a reaction can be studied easily by the reaction between sodium thiosulphate and  hydrochloric acid.

Na2S203 + 2HCl ——–> S(s) + 2NaCl(aq) + SO2(g) + H2O (l)

The insoluble sulphur, formed during the reaction, gives a milky appearance and makes the solution opaque. Therefore, rate of reaction can be studied by measuring the time taken to produce enough sulphur to make some mark invisible on a paper kept under the conical flask in which the reaction is carried out.

Apparatus

Pipette (10 ml), stop-watch, two burettes and five conical flasks (100 ml).

Materials Required

0.1 M Na2S2O3 solution and 1 M HCl solution.

Procedure

Wash the conical flasks with water and label them as 1, 2, 3, 4 and 5 respectively.

With the help of a burette, add 10, 20, 30, 40 and 50 ml of 0.1 M Na2S2O3 solution to the flasks 1, 2, 3, 4 and 5 respectively.

Now add 40, 30, 20 and 10 ml of distilled water to the flask 1, 2, 3 and 4 respectively so that volume of solution in each flask is 50 ml.

Take 10 ml of 1M HCl in a test tube with the help of a burette.

Add 10 ml of hydrochloric acid taken in a test tube to the conical flask No. 1 containing 10 ml of 0.1 M Na2S2O3 and 40 ml of distilled water and start the stop-watch.

When half of the hydrochloric acid solution has been added. Shake the contents of the conical flask and place it on the tile with a cross mark as shown in Fig.

to-study-the-effect-of-concentration-on-the-rate-of-reaction-between-sodium-thiosulphate-and-hydrochloric-acid-1