Hello, I'm currently revising unit 1 as a resit. Been fine with all the other multiple choice questions but this one (from last year's paper):
Lithium reacts with water to produce hydrogen.Li(s) + H2O(l) → LiOH(aq) + ½H2(g)I can't seem to get the right answer, which was 75%. I managed to get 75% after looking at the answer, but the method I used is unusual...
(a) In an experiment, 0.069 g (0.01 mol) of lithium produced 90 cm3 of hydrogen at room temperature and pressure. What is the percentage yield of hydrogen?
[1 mol of any gas occupies 24 dm3 at room temperature and pressure.]
Is there an actual method for doing this, without me doing these random calculations that somehow got the answer (which I don't understand how)?
I've done this weird method which involved me doing
0.01 * 24 = 0.24
0.24 * 1000 = 240
90/240 = 0.375 * 2 = 0.75
0.75*100 = 75% which is the right answer
Percentage yield calculation with gases Watch
- Thread Starter
- 02-05-2016 17:05
- 02-05-2016 17:12
Ratio of Lithium to Hydrogen gas is 1:0.5
Therefore, the moles of Hydrogen gas is half the moles of lithium. ( moles = 0.005)
volume of gas = moles * 24000 = 0.005 * 24000 = 120cm3
percentage yield = (90/120) * 100 = 75%