Note that the gas
produced is CO2
Equation:
CaCO3→CaO+CO2
1 mol CaCO3 produces 1 mol CO2
You
have 90100×10=9g pure CaCO3
Molar mass CaCO3= 100g/mol
9gCaCO3=9100=0.09molCaCO3
This
will produce 0.09 mol CO2
At STP 1mol=22.4L
0.09mol=0.09×22.4=2.016L
Hence the volume of the CO2 collected at STP when is decomposed is = 2.0L