Question

A 0.700 g sample containing Ag2O and inert material is heated, causing the silver oxide to decompose according to the following equation:
2 Ag2O(s) → 4 Ag(s) + O2(g)
If 13.8 mL of gas are collected over water at 27°C and 1.00 atm external pressure, what is the percentage of silver oxide in the sample? The partial pressure of water is 26.7 mm Hg at 27°C.

I tried doing this using the ideal gas law, but whatever I did wasn't the right answer

Answer 1

2Ag2O ==> 4Ag + O2
PV = nRT
Ptotal = pO2 + pH2O
760 = pO2 + 26.7
pO2 = 760-26.7 and convert to atm.
Solve for n = mols O2 and don't forget to convert T to kelvin.
Then ? mols O2 x (2 mols Ag2O/1 mol O2) = ? mols O2 x 2/1 = ?? Ag2O
Convert mols Ag2O to grams. g = mols x molar mass
Then %Ag2O = (mass Ag2O/mass sample*100 = ?

Answer 2

8.93