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..

how do u do this? u don't have to give the answer.. just guide and tell me the steps involved..

Answer 1

2.64 g of CO2 = how many grams of C and how many moles of C atoms? (2.64 g = 0.06 moles of CO2)
0.540 g H2O = how many grams of H and how many moles of H atoms? (0.540 g H2O = 0.03 moles of H2O)
The ratio of moles should give you the emirical formula.
0.00750 moles of the hydrocarbon yields 0.06 moles of CO2 (and of C atoms) and 0.03 moles of H2O (and 0.06 moles of H atoms).
Do you see how to finish the problem? (Hint: 0.0075 moles = X grams of C and Y grams of H; mass = X+Y = 0.0075 mol)

Answer 2

Since you have the grams of CO2 and water produced it is easy to calcualte moles. Just divide by the repective mol. mass of each compond.

Now realize that all of the carbon in the CO2 came from the hydrocarbon. Similarly all of the Hydrogen is in the water. So calculate the grams of carbon in the CO2 (carbon will be 12/44) and the hydrogen in the water (it will be 2/18).

Now that you have the grams of C and H you can calculate the empirical formula inthe usual way.

Since you have the strting moles of the hydrocarbon and you have the grams of carbon and hydrogen, youcan also calculate the molecular formula compared to the empirical formula.

Sounds like fun