Chemistry Question... (1 Viewer)

[horseluver29]

Ok what do you guys think of this question? I may be approaching it wrong, or it may just be a case of strange rounding off, but the question is:

If KCl and 4.60g of O2 are obtianed from heating 42.00g of KClO3, what is the mass percent yield of O2?
a) 62.92
b) 55.93
c) 41.94
d) 17.01
e) 27.96

I have done it like 10 times and keep getting 39 point something without any rounding during the calculations (except where my calculator rounds to), and 40 point something if I tweak where I round the numbers to after each step of the calculation.

Is it just a rounding thing or am I way off?

Thanks guys

 

[horseluver29]

Oo oo hang on I think I've got it!

Whilst the O2 is the limitng reagent in this instance, if it wasn't you would have the potentail to obtain 16 point something grams of O2 from the 42 grams of KCLO3...
(4.6/16 point something) x 100 = 27.96%

Yay