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Calculate the volume (in L) of gas evolved on complete thermal decomposition of a dolomite ore sample at 1 atm and STP (273 K). The sample contains 1% pure dolomite [CaMg(CO3)2] by mass. Total mass of sample = 18.4 kg. (Assume no volatile impurity; use molar volume = 22.4 L/mol at STP.)

1. 22.4
2. 44.8
3. 89.6
4. 179.2

Correct answer: 44.8

Solution

Thermal decomposition: CaMg(CO3)2 -> CaO + MgO + 2CO2. With 1 mol of pure dolomite (184 g) obtained from the sample, 2 mol CO2 is produced, occupying 2 * 22.4 = 44.8 L at STP.

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