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# Ocr gateway CHEM 4 5 6 markscheme Watch

1. Normally high 50s/low60s range dependent on difficulty

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2. (Original post by Meganward123)
can someone please explain the concentration 6 marker?
I worked out that there were 0.0025 moles, 0.0025/(20/1000) equals 0.125 mol/dm3
I used the equation- Volume (acid) x Concentration (acid)= Volume (alkali) x Concentration (alkali)
3. 1920 cm^ 3 for the volume question using 24000cm3

0.08 moles

0.08 was the conc of sodium hydroxide in the 6 marker at 20 cm was the end point
4. (Original post by Swagswag1963)
1920 cm^ 3 for the volume question using 24000cm3

0.08 moles

0.08 was the conc of sodium hydroxide in the 6 marker at 20 cm was the end point
Yes I agree.

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5. (Original post by Rjhepkenhdjd)
do you know what the grade boundaries for it are normally like in general? ty !!
Going off last year, it was 60 for an a*, 50 for an A, decreasing each time by 10 marks.
C1,2,3 was 61 for an A*
6. (Original post by Meganward123)
can someone please explain the concentration 6 marker?
I worked out that there were 0.0025 moles, 0.0025/(20/1000) equals 0.125 mol/dm3
concentration of acid x volume acid = concentration of alkali x volume alkali

This is the equation u use for titrations.

So u fill it in

0.1*40=?* 25

?= (0.1*40)/25
7. (Original post by esmithxx)
I used the equation- Volume (acid) x Concentration (acid)= Volume (alkali) x Concentration (alkali)
Thanks Emily!
8. (Original post by Meganward123)
can someone please explain the concentration 6 marker?
I worked out that there were 0.0025 moles, 0.0025/(20/1000) equals 0.125 mol/dm3
I did it like so:
Moles = concentration*volume
Moles HCl = 0.1 * 20/1000 (convert to dm3) = 0.002

HCl:NaOH
1:1
0.002:0.002

Concentration = moles/volume
Concentration NaOH = 0.002/(25/1000)
= 0.002/0.025 = 0.08

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9. what was the answer to how much pesticide was used for country E
10. (Original post by JickDee)
what was the answer to how much pesticide was used for country E
1,260,000,000 ???

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11. (Original post by mxskaan)
1,260,000,000 ???

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Didn't you have to multiply that by 0.18
12. (Original post by mxskaan)
1,260,000,000 ???

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I got something like that too
13. (Original post by happiness12)
I got something like that too
14. (Original post by ellamoon_22)
I got 0.16 for the titration six marker
15. (Original post by ellamoon_22)
Didn't you have to multiply that by 0.18
16. (Original post by haithamnhaque)
I got 0.16 for the titration six marker
It was 0.08
17. (Original post by haithamnhaque)
I got 0.16 for the titration six marker
Sme bit everyone sed end point was 20 idk
18. What was the answer to the question where it asked what mass would be produced with 20.6 amps instead of 10.3 for 120 minutes ???
i got 60 g
19. (Original post by ellamoon_22)
I just read the titration page and you are supposed to use the point of neutralization. That means it is not 0.16
20. (Original post by happiness12)
What was the answer to the question where it asked what mass would be produced with 20.6 amps instead of 10.3 for 120 minutes ???
i got 60 g
Yeah I think I got that too.

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Updated: June 21, 2016
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