Question

(a) Explain the effect of temperature and catalyst on the rate of a reaction.
(b) State Faraday's first law of electrolysis.
A solution of $CuS{O}_4$ is Electrolysed for 10 minutes with a current of 1.5 amperes. What is the mass of copper deposited at the cathode?

Answer 1

(a) The effect of temperature on the rate of a reaction:
(i) With increase in temperature, intermolecular collisions will be more violent. This will result in higher molecular velocities and less time between collisions. The collision frequency and the number of effective collisions will increase which will increase the rate for the reaction. For every 10 degree rise in temperature, the rate of reaction is roughly doubled.
(ii) The effect of catalyst on the rate of a reaction:
A catalyst provides an alternate pathway of lower activation energy and increases the rate of the reaction.
(b) Faraday's first law of electrolysis:
The amount of the substance that undergoes oxidation or reduction at each electrode during electrolysis is directly proportional to the amount of electricity that passes through the cell.
Thus mass of the substance produced
$=\frac{\text{I(A)}\times \text{t(s)}}{{\text{96500 C/mol e}}^{-}}\times \text{mole ratio}\times \text{molar mass}$
Here I(A) is current in ampere and t(s) is time in second.
Number of moles of electrons passed
$=\frac{I\left(A\right)\times t\left(s\right)}{96500}=\frac{1.5\times 10\times 60}{96500}=0.009326$ moles of electrons
$C{u}^{2+}+2e^{-}\to Cu$
The number of moles of copper deposited $=\frac{0.009326}{2}=0.004663$ moles.
The molar mass of Cu is 63.5 g/mol.
The mass of Cu deposited $=0.004663mol\times 63.5g/mol=0.296g$