# Of each of these equations, determine the change in the number of moles (change in n gas)

Of each of these equations, determine the change in the number of moles (change in n gas)

(a) (NH4)2CO3(s) yields 2NH3 (g) + CO2 (g) + H2O (g) ___________ mol
(b) H2 (g) + Cl2 (g) yields @HCl (g) ___________ mol
( c) 2H2 (g) + O2 (g) yields 2H2O (l) ___________ mol
(d) 2Na (s) + Cl2 (g) yields 2NaCl (s) ___________ mol

Approach these problems through the following steps:

1. Balance the chemical equation. Make sure there are the same number of moles of each element on each side of the equation.
ex.) The unbalanced exquation for the dissociation of water is
H2O --> H3O+ + HO-
If we balance it we get
2 H2O --> H3O+ + HO-
Because there are four hydrogen atoms in the products there must be four hydrogen atoms in the reactants

2. Once the equation is balanced, to find the change in the number of moles of gas, we simply subtract the sum of the coefficients of the gases that are reactants from the sum of the coefficients of the gases that are products.
ex.) (NH4)2CO3(s) --> 2NH3 (g) + CO2 (g) + H2O (g)
we see that none of the substances in the reactants are gasses so the sum of coefficients of the gases that are reactants = 0
In the products, however, we see that all three substances are gases. We take the sum of their coefficients and we get 4 (Think 2+1+1 = 4).

To find the change in the number of moles of gas we then subtract the number of moles of reactants that are gases from the number of moles of products that are gases. Because none of the reactants are gases, and there are four moles of gases in the products we get 4 - 0 = 4.
The change in the number of moles is 4

The changes in moles for B) = 0, C) = -1, D) = -1