Question

14.34 g of an oxide of lead was heated in a stream of dry hydrogen, 12.42 g of lead was obtained. Relative atomic masses of oxygen and lead are 16 and 207 respectively.
1. How many grams of oxygen were presthe oxide?
2. Calculate the number of moles of oxygen atoms present.

Answer 1

PbO₂ + H₂ -> Pb + H₂O
1Mol 1Mol

n(PbO₂)=14,34/239=0,06Mol
n(Pb)=12,42/207=0,06Mol
PbO₂ reacted completely
PbO₂ -> 2O
239g/mol/14,34g=32g/mol/x
m(O)=1,92g
n(O)=m/n=1,92g/16g/mol=0,12mol