Question

How much work is done on (or by) the gases in each of the following at 298 K and 1 atm?

reaction of 5.3 g of H2(g) with 4.0 g of CO2(g) to produce H2O(g) and CO(g)

decomposition of 13.4 g KClO₃ into KCl(s) and O₂(g)

Answer 1

1) the reaction is

H2 (g) + CO2 (g)--> H2O(g) + CO (g)

We know that work = -change in number of moles X R X T

Here change in moles of reactant to product = 0

So work done = 0

2) the reaction will be

KCLO3(s) --> KCl (s) + 3/2 O2(g)

Work done =- Change in moles X R X T

Change in moles is positive so work will be done by the system

1 mole fo KClO3 will give 3/2 moles of O2

so moles of O2 produced by 13.4 grams will be

Molecular weight = 122.5 gram / mole

So moles of KCLO3 = 13.4 /22.5 = 0.109 moles

Moles of O2 produced = 0.164 moles

So work =- 0.164 X 8.314 X 298 = -408.79 Joules