Question

How many molecules of oxygen are produced from the decomposition of 8.75 g of hydrogen peroxide in the following equation Mg + H2O2 --> MgH2 + O2

options:

8.75 x 1024


6.02 x 1023


1.55 x 1022


5.27 x 1024


1.55 x 1023

Answer 1

Here is a worked example of a stoichiometry problem. Just follow the steps.
http://www.jiskha.com/science/chemistry/stoichiometry.html

Answer 2

8.75/34.02 (molar mass of H2O2) = .257 mol H2O2

Since the mol ratio b/t H2O2 and O2 is 1:1, there is also .257 mol O2

.257 mol * 6.02 * 10^23 = 1.55 * 10^24 molecules so the 3rd option.