Question

How much (moles) of AgO can you form from 0.450 mol Ag2O with 0.300 mol O2?

Ag2O + O2 = AgO​

Answer 1

Balance the reaction:

a Ag₂O + b O₂   →   c AgO

Count the atoms on either side:

• Ag : 2a = c

• O : a + 2b = c

Suppose a = 1. Then immediately c = 2, and it follows that b = 1/2, so that the balanced reaction is

1 Ag₂O + 1/2 O₂   →   2 AgO

or, with integer coefficients,

2 Ag₂O + 1 O₂   →   4 AgO

This tells you that 4 mol AgO are produced for every 2 mol Ag₂O and 1 mol O₂.

Since 0.450/2 = 0.225 < 0.300, we end up consuming all of the starting Ag₂O, and produce 4/2 × 0.450 = 0.900 mol AgO.