# Markscheme's WRONG, could you please double check 2 of my answers? :)

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Thread starter 5 years ago
#1
I'm okay with (a)!
I just want to know if my answers to (b) and especially (c) are right ?

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5 years ago
#2
(Original post by Adorable98)
I'm okay with (a)!
I just want to know if my answers to (b) and especially (c) are right ?

G
Mark scheme is right.

First answer mark scheme gives cm3 and you used dm3. Both right.

Second answer you are wrong.
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Thread starter 5 years ago
#3
(Original post by TeachChemistry)
Mark scheme is right.

First answer mark scheme gives cm3 and you used dm3. Both right.

Second answer you are wrong.
Really?
Why is my second answer wrong?! I even used a calculator to double check my answer and I was right (I guess)?
3.087 + 10% = 3.187 not 3.40 or the other no. mentioned in the mark scheme?!
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5 years ago
#4
(Original post by Adorable98)
Really?
Why is my second answer wrong?! I even used a calculator to double check my answer and I was right (I guess)?
3.087 + 10% = 3.187 not 3.40 or the other no. mentioned in the mark scheme?!

What is 10% of 3.087?
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5 years ago
#5
Man this takes me back...and I was **** at Chemistry...sigh.

As said above your answer in dm and theirs in cm is the same, albeit I think you see cm(3) more often, doesn't matter though.

Last one you haven't added 10% in your calculation, you seem to have added 0.1 to 3.0875 to get your 3.1875. Where as 10% of 3.0875 is 0.30875, so 3.0875+0.30875=3.396, or just multiply 3.0875 by 1.1 as they do.

Btw out of curiosity what exam is this from?
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5 years ago
#6
(Original post by Adorable98)
Really?
Why is my second answer wrong?! I even used a calculator to double check my answer and I was right (I guess)?
3.087 + 10% = 3.187 not 3.40 or the other no. mentioned in the mark scheme?!
10% is one tenth

one tenth of 3.087 is 0.3087

add these together

3.087
0.309
-------
3.396

which is 3.40 to 2 dp
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Thread starter 5 years ago
#7
(Original post by TeachChemistry)
What is 10% of 3.087?
10 x 3.078 .. I see
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Thread starter 5 years ago
#8
(Original post by joey11223)
Man this takes me back...and I was **** at Chemistry...sigh.

As said above your answer in dm and theirs in cm is the same, albeit I think you see cm(3) more often, doesn't matter though.

Last one you haven't added 10% in your calculation, you seem to have added 0.1 to 3.0875 to get your 3.1875. Where as 10% of 3.0875 is 0.30875, so 3.0875+0.30875=3.396, or just multiply 3.0875 by 1.1 as they do.

Btw out of curiosity what exam is this from?
It's from the Edexcel (2007) GCE Sample assessment material!

https://qualifications.pearson.com/c...-chemistry.pdf
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Thread starter 5 years ago
#9
(Original post by charco)
10% is one tenth

one tenth of 3.087 is 0.3087

add these together

3.087
0.309
-------
3.396

which is 3.40 to 2 dp
Cheers!
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5 years ago
#10
(Original post by Adorable98)
10 x 3.078 .. I see
No? It would be 0.1*3.078

Anyway what you should be doing is 1.1*3.087, that saves messing about
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Thread starter 5 years ago
#11
(Original post by langlitz)
No? It would be 0.1*3.078

Anyway what you should be doing is 1.1*3.087, that saves messing about
Really? Doesn't 10% excess mean you should mutiple by 0.1?! And where did you get 1.1 from?
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5 years ago
#12
(Original post by Adorable98)
Really? Doesn't 10% excess mean you should mutiple by 0.1?! And where did you get 1.1 from?
Multiplying by 0.1 gives you 10% and then you need to add on the original. Multiplying by 1.1 skips a step and just gives you the final answer.

Have you ever learnt maths?
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5 years ago
#13
(Original post by Adorable98)
Really? Doesn't 10% excess mean you should mutiple by 0.1?! And where did you get 1.1 from?
What I'm seeing from you here is a fundamental lack of understanding of how to use percentages. This is rather worrying to see in an A level chemistry student. You should pick up a maths book and learn about percentages.
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