I've tried to solve them several times, but I couldn't manage to do it, so, if you guys could help, I'd appreciate it.
These are from a test to win scholarships abroad, so I already have the answers, but I don't know how to solve them...
1) A 40,0L sample of N
2 gas containing SO
2 gas as an impurity was bubbled through a 3% solution of H
2O
2. The SO
2 was converted to H
2SO
4:
SO
2 + H
2O
2 H
2SO
4A 25,0mL portion of 0,0100mol/L NaOH was added to the solution, and the excess base was back-titrated with 13,6mL of 0,0100mol/L HCl. Calculate the ppm of SO
2 (that is, mL SO
2/10^6mL sample) if the density of SO
2 is 2,85g/L. (Atomic weights: H=1 N=14 O=16 Na=23 S=32 and Cl=35,5).
2)Exactly 4,32g of oxygen gas was required to completely burn a 2,16g sample of a mixture of methanol and ethanol. Answer the following questions (a) and (b). (Atomic weights: H=1 C=12 and O=16)
a)How many moles of ethanol are contained in the sample?
b)What is the percentage by weight of methanol in the sample? Write the percentage to two significant figures.
By the way, the answers are:
1) 32,0 ppm
2) a)0,04 mol b)15%
Thanks a lot