GCSE ('O' level) Chemistry Question
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During steel making, sulphur is removed from molten iron by adding magnesium:
Mg + S --> MgS
If a 100 tonne batch of molten iron contains 0.25% sulphur, how many kilograms of magnesium are needed to remove it?The title is misleading, as this really is more GCSE standard. It's nearly 2am though and I'm spent after having had many an exam today. I've done this but got approximately 189 kg. I've got the feeling it is incorrect, and I'm wondering if someone can either see my mistake from the answer or guide me through it.
Thanks.
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Your working is correct.
For GCSE and A/AS level, they uses different periodic table. Your periodic table is for A/AS.
For GCSE
0.25% of 100 tonne = 250 kg
mol of sulphur present = 250 000 / 32 = 7812.5 mol
Reaction ratio Mg : S = 1: 1
therefore mass of of Mg needed = 7812.5 mol x 24 = 187.5 kg
For A / AS Level
0.25% of 100 tonne = 250 kg
mol of sulphur present = 250 000/ 32.1 = 7788.2 mol
Reaction ratio Mg : S = 1: 1
therefore mass of Mg needed = 7788.2 mol x 24.3 = 189.25 kg
Best regards,
Chin Seng
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Hi guys,
I'm getting this:
A 100 tonne batch of molten iron contains 0.25% sulphur
0.25% of 100 tonnes is 0.25 tonnes of S
Equation given as:
Mg + S --> MgS
1 mole of S : 1 mole of Mg
32 g of S: 24 g of Mg [the mass of the Mg required is less (not more) than the mass of S]
32 kg of S: 24 kg of Mg
32 tonnes of S: 24 tonnes of Mg
0.25 tonne of S: (24/32)X0.25 tonne of Mg = 3/16 tonne of Mg = 187.5 kg
Thanks.
Sincerely,
CKLee
Founder,
OpenlySolved.org -- free solutions to math textbook questions!
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DarknessHacker and CKLee are of course, totally correct. My screw-up, my bad.
Btw CKLee I see you're now using a forum format for your website. Nice upgrade!
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Hi Ultima,
Thanks -- it was a suggestion from a student who felt a long list of links to PDF files were very 1990s. I made him install the forum software! 8-)
CKLee