AQA Synoptic questions help

Hi,
Im a bit confused with these two questions and would really appreciate if someone could have a look at them for me.
1. A particular sample of iron ore contains 85% by mass Fe2O3 (Mr=159.6) and no other iron compound. the maximum mass of iron that could be extracted from 1.0 tonne of this ore is:
A 0.59tonne
B 0.66 tonne
C 0.75 tonne
D 0.85 tonne
I thought the answer was D :s-smilie:

but its incorrect can someone please explain to me what im doing wrong? the answer is A
2. Which one of the following does not have a singlet peak in its proton n.m.r spectrum?
A butylmethanoate
B propylethanoate
C ethylpropanoate
D methyl butanoate
I know that A and D have got singlets...I personally thought B was the answer however the markscheme says C :confused:

is it an error or am i making a silly mistake???
Thanks in advance

Reply 1

EierVonSatan

1000000g/159.6 = 6265.66mol of Fe2O3 ---> 2Fe = 12531mol of Fe extracted (2:1 ratio) this is 701,754g of Fe - ore is 85% pure so 701,754g*0.85 = 596491g = 0.59 tonnes (more or less with rounding)

The following protons give rise to singles in proton nmr (bold)
A butylmethanoate - HCO2CH2CH2CH2CH3
B propylethanoate - CH3CO2CH2CH2CH3
C ethylpropanoate - CH3CH2CO2CH2CH3
D methylbutanoate - CH3CH2CH2CO2CH3

Reply 2

Anonymous1783

I can see why you think it would be D but when you read the question carefully it asks for the maximum mass of iron not maximum mass of Fe2O3. So firstly you find the maximum mass of Fe2O3, ie what you did 1 * 0.85 =0.85 tonnes. But that is the maximum mass of Fe2O3 not Fe. So you then find the mass of iron in that using the mr. The Mr of iron is Fe2 so 55.8*2 =111.6, you then find this as a percentage of the total mr for Fe2O3. So 111.6/159.6 = 0.71.
0.85 * 0.71 = 0.60

Well that is probably a rounding error but its close enough