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0.0075 mole of calcium trioxocarbonate (IV) is added to 0...

0.0075 mole of calcium trioxocarbonate (IV) is added to 0.015 mole of a solution of hydrochloric acid. The volume of gas evolved at s.t.p is?
[Molar volume of a gas at s.t.p = 22.4 dm3]

A.

224cm3

B.

168cm3

C.

112cm3

D.

100cm3

Correct answer is B

1mole of gas at STP = 22.4dm3
0.0075 mole of CaCO3  = xdm3

cross multiply;

where 22.4dm3 = 22400cm3

x * 1 = 0.0075 * 22400 → 168cm3

 the gas CO2 which evolved was gotten from CaCO3 so we use the number of moles of CaCO3 only