On complete combustion, 0.00750 mol of a hydrocarbon X gave 2.64g of carbon dioxide and 0.540g of water.?

Question

the question asks us to calculate (i) the number of moles of CO2 produced.. (ii) the no. of moles of water produced.. (iii) determine the molecular formula of X..

i noe how to do (i) and (ii) but how do u do (iii)? thanx

i get C1H1.. is tat correct?

maussy.. thanx alot.. yours makes a lot of sense now.. i was wondering what to do wit the 0.00750 mol of hydrocarbon..

Answer 1

amole of CO2 has a mass of 12+2*16=12+32=44g
so (i)2.64g = 2.64/44=0.06mole of CO2
(2) a mole of water has a molar mass of 18g
(ii) 0.54/18 = 0.03mole of water
(iii) When burning an hydrocarbon gives
CnHm+(n+m/2) O2---> nCO2 + m/2 H2O
n=0.06 accoding to(i) m/2 = 0.03 with (ii) so m=0.06
the formula of the hydrocarbon as n=m is Cn Hn
the mass of carbon burned is 2.64*12/44=0.72g
The mass of hydrogen burned is 0.540*2/18=0.06g
0.72+0.06=0.78g
this corresponds to 0.0075mole
so 1 mole =0.78/0.0075=104g
the formula is C8H8