Group Presentation : 5 Neptune 2011

Group Work : Download

8/2/2011 : Given the group assignment.

Group work rate of reaction

SAMPLE ANSWER

Question 1 :
(i) Use zinc powder in excess. More total surface area of zinc atom exposed for collisions. Frequency of collision between zinc atom and hydrogen ion were increased. Frequency of effective collision between zinc atom and hydrogen ion also increased. Rate of reaction higher.

(ii) Zn + H₂SO₄ → ZnSO₄ + H<sub>2

∴1  mol</sub> H₂SO₄ → 1 mol H₂

no of mole H₂SO₄= 50 (2) / 1000 = 0.1 mol

 _{∴0.1  mol} H₂SO₄ → 0.1 mol H₂

Volume of gas given off = 0.1 x 24 = 2.4 dm³

SAMPLE ANSWER

Question 2 :
(i) Change the concentration of acid.
First way :
Double concentration of hydrochloric acid to 4 mol dm^-3 and halved the volume of acid to 25 cm³.
Second way :
Using sulphuric acid 2 mol dm^-3 and halve the volume of acid to 25 cm³.

Concentration of hydrogen ion per unit volume increased. Frequency of collision between zinc atom and hydrogen ion increased. Frequency of effective collision between zinc atom and hydrogen ion also increased. Rate of reaction higher.