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.