Chemistry help!! Quick!

[nox_fjmoony]

So hey we were being taught the mole concept for AS and well my our teacher gave us some problems and then he explained and solved them. Well, I just copied them down and well now that I've mulled over these at home, I'm having problems with his solutions, looks like they've been sorta patched up an all, to match with the real answers or sth. Idk, I don't know where he got these probs from , so I can't check. So if anyone out there could help me, I'd be really happy, I'm having a class test on Tuesday and I need to clear my problems as soon as possible. Ok. Here are the problems. Also, an explanation with the solution would be very appreciated.

Problems:

1)150cm³ of oxygen was added to 20cm³ of a gaseous hydrocarbon. After explosion and cooling the gaseous mixture occupied 130cm³. And after absorption by potassium hydroxide, 90cm³ of oxygen remain. Calculate the molecular formula of the hydrocarbon. [we were using this to solve it : C_xH_y+ (x+y/4)O₂-------> XCO₂+ Y/2H₂O]

[edit] Found another problem.
2) One brand of antacid chewing gum contains 2.5% by mass of urea. Given that urea reacts with ethanoic acid as follows:
NH₂CONH₂ + 2CH₃COOH + H₂O --------> CO₂+ 2CH₃COONH₄

What mass of chewing gum is required to neutralise 1g of ethanoic acid?

Ok thats all for now, I may be posting more problems as they come up. Thanks again.

[astarmathsandphysics]

Tricky question. From my limited knowledge of chem I know it is to do with the ratios of the volumes cos the same numbers of moles of any gas occupies the same volumes. I will try it today. I think I can do it.

[nox_fjmoony]

Awesome
yeah, its done using that
But my problems not there, its just that my teachers sorta ya know, tried to make his answer end up like the book answer, so I kinda got confused. Well, now I got another problem.
T_T