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# Chemistry Difficult GCSE question! Help! watch

1. Iron is extracted by heating iron oxide with carbon monoxide.

Fe2 O3 + 3CO -----> 2Fe + 3CO2

a) Calculate the theoretical yield of iron that can be obtained when 320kg of iron oxide (Fe2 O3) reacts with excess carbon monoxide.

b) The actual yield of iron is 100kg. Calculate the percentage yield of iron.

This is really hard and not straight forward, I have got an answer that I have worked out, but not sure if it's right, could a really good chemist student work it out and see if what they got? My answers are in the spoilers. Thank You!!

Spoiler:
Show

a) 146.9kg
b) 68.1%
2. I roughly got 224kg using my crappy phone calculator (could have easily made a mathematical error but the actual method is the same). But I worked it out doing:
excess CO so all 320kg fe2 O3 will react.
find the number of moles of fe2 O3 in 320kg ( 320 * 1000 to covert kg to grams)
2:1 ratio so times number of moles of fe2 O3 by 2 to get moles of fe (iron)
convert moles of iron to grams of iron
finally divide by 1000 to get kg of iron
Iron is extracted by heating iron oxide with carbon monoxide.

Fe2 O3 + 3CO -----> 2Fe + 3CO2

a) Calculate the theoretical yield of iron that can be obtained when 320kg of iron oxide (Fe2 O3) reacts with excess carbon monoxide.

b) The actual yield of iron is 100kg. Calculate the percentage yield of iron.

This is really hard and not straight forward, I have got an answer that I have worked out, but not sure if it's right, could a really good chemist student work it out and see if what they got? My answers are in the spoilers. Thank You!!

Spoiler:
Show

a) 146.9kg
b) 68.1%

The answers should be 224 kg and 44.6% respectively.

Perhaps you can show your working so we could figure out where the mistake occurred.
4. (Original post by Metanoia)
The answers should be 224 kg and 44.6% respectively.

Perhaps you can show your working so we could figure out where the mistake occurred.
I kinda did it on a draft paper then threw it away... oops, sorry. But is it ok if you pm me and show me how you worked it out? Would be really helpful!
5. (Original post by Ethan9133)
I roughly got 224kg using my crappy phone calculator (could have easily made a mathematical error but the actual method is the same). But I worked it out doing:
excess CO so all 320kg fe2 O3 will react.
find the number of moles of fe2 O3 in 320kg ( 320 * 1000 to covert kg to grams)
2:1 ratio so times number of moles of fe2 O3 by 2 to get moles of fe (iron)
convert moles of iron to grams of iron
finally divide by 1000 to get kg of iron
How did you find out the ratio of the moles??
6. method 1: Using mole ratios

Moles of Fe2O3 = 320 000/160 = 200 moles

Expected moles of Fe = 200 x 2 (because 1Fe2 O3 + 3CO -----> 2Fe + 3CO2 )
= 400 moles

Mass of 400 moles of Fe = 400 x 56 = 22400 g = 224 kg

method 2: Using fraction by mass

"Mr" of Fe in Fe2O3
Mr of Fe2O3

= 2 x 56
(2 x 56 + 3 x 16)

= 0.7

Mass of Fe from 320 kg of Fe2O3 = 0.7 x 320kg = 224 kg
How did you find out the ratio of the moles??
The number (after balancing the equation) in front of each species in the equation represents the molar ratio of that species. In this instance, for every mole(no number in front means theres one mole) of Fe2 O3 that reacts there are two moles of Fe that form.

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Updated: October 15, 2017
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