How much marble of 96.5% puriety would be required to prepare 100 litres of carbon dioxide ar S.T.P. when marble in acted upon by dil HCl ?

The heat of combustion of ethane gas is 373 K Cal per mole. Assuming that 50% of heat is lost, how many litres of ethane measured at S.T.P. must be burnt to convert 50 kg of water at 10^@C to steam at 100^@C ? One mole of gas occupies 22.4 litres at S.T.P. Latent heat (L) of steam = 2.25 xx 10^6 J k^-1 .