Chemistry help needed

[markiola]

I have a problem with doing question 7 a) i. (2008 november)
http://www.xtremepapers.me/CIE/Cambridg ... _qp_03.pdf
Could anyone help?
Thanks in advance

 

[HyDraZin3]

Here,mole ratio is same as volume ratio.So 1 mole of butane reacts with 6.5 moles of oxygen therefore volume of oxygen should be 10*6.5=65cm^3
Now volume of oxygen left=100-65=45
and volume of CO2 is 10*4 =40