i.Calculate the volume of carbon ivoxide given off at stp when 20gram of octane is burnt in excess air (c=12,1+=1 gmv of any gass is 22.4dm^3 at stp). ii. Deduce the formula of a hydrocarbon with general formula cnH2n-2 of its molar mass in 110.

Answer 1

C8H16 + 12O2 ==> 8CO2 + 8H2O
mols C8H18 = grams/molar mass = ?
Using the coefficients in the balanced equation, convert mols C8H18 to mols CO2.
Then mols CO2 x 22.4 dm^3/mol = ?dm^3 CO2

ii.
CnH2n-2 has an empirical mass of
12n + 2n - 2 = 110
14n = 108
n = about 7.7 which rounds to 8 so
C8H(2*8-2) = C8H14
Check: 12*8 = 96
14*1 = 14
96+14 = 110.