(a) If L is the Avogadro constant… | Chemistry

Question 1 Report

(a) If L is the Avogadro constant and E° is standard cell potential, state what X and Y stand for in the following expressions

(i) X = \(\frac{\text{Mass of L molecules of gas or vapour}}{\text{ Mass of L molecules of hydrogen}}\)

(ii) Y = -nFE°

(b) State two differences between a primary cell and a secondary cell.

Answer

Answer Details

(a)

(i) \(X = \dfrac{\text{mass of L molecules of gas or vapour}}{\text{mass of L molecules of hydrogen}}\) is the relative density (vapour density) of the gas. Because L molecules is one mole, this ratio equals the molar mass of the gas divided by the molar mass of hydrogen, i.e. relative density \(= \tfrac{1}{2}\times\) molar mass.
(ii) \(Y = -nFE^\circ\) is the standard change in Gibbs (free) energy of the cell reaction, \(\Delta G^\circ\), where n is the number of moles of electrons transferred and F is the Faraday constant.

(b) Two differences between a primary cell and a secondary cell:

Primary cell	Secondary cell
Cannot be recharged; used once and discarded.	Can be recharged and used repeatedly.
The cell reaction is irreversible.	The cell reaction is reversible.
Example: Leclanche (dry) cell.	Example: lead-acid accumulator.

(a) If L is the Avogadro constant and E° is standard cell potential, state what X and Y stand for in the following expressions (i) X = \(\frac{\text{Mass of...