Question

How much gas will be produced at 0 deg centigrade and 760 mm of pressure when 10g of oxalic acid was heated with concentrated sulphuric acid?

Answer 1

Oxalic acid when heated with Concentrated sulphuric acid, decompose into carbon dioxide, carbon monoxide and water. 

Sulphuric acid is a dehydrating agent.

According to the reaction, 1 mole of oxalic acid produce 1 mole of CO₂ and 1 mole of CO gas.
Molar mass of oxalic acid (C₂H₄O₂) = 126.03 g/mol     ( oxalic acid is always present as dihydrate C₂H₄O₂.2H₂O in solid state)
Number of moles of oxalic acid in 10g = 10126.03= 0.079 moles

Thus according to the reaction 0.079 moles of CO and 0.079 moles of CO₂ will be produced.
Now at STP (0⁰ celcius and 760 mmHg pressure) 1 mole of gas will occupy volume = 22.4 L
​Thus volume of 0.079 mole of  a gas = ​22.4×0.079 L
                                                  = 1.77 L
Thus there will be 1.77 L of CO₂ and 1.77 L of CO gas. 

Thus total volume of gas will be 3.54 L.