There are two or three ways of approaching this. The simplest way, but one that doesn't really cinch an answer is this.
Use PV = nRT. Solve for n = number of mols. Then n = g/molar mass. You have n and g, solve for molar mass. I get 42 for that. The molar mass of A is 26, B is 39, C is 42 and D is 44. So you assume C is the answer but it doesn't leave much room for rounding errors and that kind of thing.
If you wish to confirm that you can do this.
Use PV = nRT and convert 20 cc H2O to moles and convert 40 cc CO2 to moles.
Then grams = mol x molar mass; convert H2O and CO2 to grams H and grams C.
Add g H and g C and subtract from mass sample to find g oxygen (O, not O2).
Then convert g C, g H, g O to moles . moles = grams/molar mass
Finally, find the ratio of the elements to each other and that comes out CH2O.
0.0337g of a volatile liquid when vaporized completely at 100Pa and 300K occupied a volume of 20cm3. When this volume of vapor was completely burnt in an excess of oxygen, 40cm3 of carbon dioxide and 20cm3 of water vapor were formed. All volumes being measured at the same temperature and pressure. What is the formula of the compound? A: C2H2 B: C3H3 C: CH2CO D: CH3CHO
2 answers
If PV=nRT, (100)(2x10^-5)=(n)x(8.31)x(300), n is 8.02x10^-7. How did you manage to get the mr of 42?
1 answer