For each of the equations, determine the change in the number of moles of gas, Δ𝑛gas .

Question

(NH4)2CO3(s)⟶2NH3(g)+CO2(g)+H2O(g)

Δ𝑛gas=mol?

H2(g)+Cl2(g)⟶2HCl(g)

Δ𝑛gas=mol?

2H2(g)+O2(g)⟶2H2O(l)

Δ𝑛gas=mol?

2Na(s)+Cl2(g)⟶2NaCl(s)

Δ𝑛gas=mol?

Answer 1

Simply take the difference between the number of moles of gas on the product side and the reactant side of the equation.

(NH4)2CO3(s)⟶2NH3(g)+CO2(g)+H2O(g)

moles of gas on product side = 2 + 1 + 1 = 4

moles of gas on reactant side = 0

∆ngas = 4 - 0 =4 mol

H2(g)+Cl2(g)⟶2HCl(g)

moles of gas on product side = 2

moles of gas on reactant side = 1 + 1 = 2

Δ𝑛gas = 2 - 2 = 0 mol

You should be able to do the rest. And yes, it is possible to get a negative number which you will get in the next two examples.