2016 IGCSE Chemistry Paper 2 Unofficial Mark Scheme 2016

For "why do you heat the acid" i said to help the solid dissolve. Would i get it for that? And also for the excess one is it that the solid will sink to the bottom of the beaker?

Quoting from the mark scheme:to increase the rate/speed(of the reaction)

IGNORE to start the reaction/to provideenergy/references to the copper(II) oxidewill not react without heat / to make itdissolve faster / to give particles more
energy.

ACCEPT:to overcome the activationenergy/to provide activationenergy (for the reaction)

Reply 121

Castro300

12

Original post by jamesj477

The insoluble impurities were removed at stage 2, as they were filtered out, leaving salt water.
Other 2 are correct

Yes, exactly, that was stage 3, and thats what most people said in my school, for that reason.

Reply 122

Niclewis

1

for the volume of oxygen one, is it that the volume decreases because the oxygen reacts with the iron but then stops decreasing after 2 weeks because all the oxygen has been used up?

Reply 123

Lelanor

14

Original post by Cheekymonkey2311

If i times it by 3 instead of dividing it by 3, how many marks do you reckon i would get, if any?

I cant remember what it was out of. If it was out of 3, I'd say probably 1 mark, but if it was out of 2 then probably 0 (although I'm no expert on marks schemes, so don't take my word for it)

Reply 124

aaliya23

did the concordat question say pick three numbers?

Reply 125

Niclewis

1

Original post by Castro300

Yes, exactly, that was stage 3, and thats what most people said in my school, for that reason.

no i think the sand was removed in stage 2 but the impurities were removed in stage 6

Reply 126

jamesj477

10

Original post by Abodee1

Quoting from the mark scheme:to increase the rate/speed(of the reaction)

IGNORE to start the reaction/to provideenergy/references to the copper(II) oxidewill not react without heat / to make itdissolve faster / to give particles more
energy.

ACCEPT:to overcome the activationenergy/to provide activationenergy (for the reaction)

Lol I didn't know so I mashed 2 answers in one, I said it will increase the solubility so more copper oxide will react, therefore speeding up the rate of reaction. Doesn't really make sense tho but o well

Reply 127

Castro300

12

Original post by Abodee1

Quoting from the mark scheme:to increase the rate/speed(of the reaction)

IGNORE to start the reaction/to provideenergy/references to the copper(II) oxidewill not react without heat / to make itdissolve faster / to give particles more
energy.

ACCEPT:to overcome the activationenergy/to provide activationenergy (for the reaction)

Oh no, i put increase rate AND start reaction. Im guessing the ignore cancels out the accept. But is that for reject though, and not ignore

Reply 128

jamesj477

10

Original post by Niclewis

no i think the sand was removed in stage 2 but the impurities were removed in stage 6

The sand was removed at stage 2, but the impurities were INSOLUBLE, so they did not dissolve, so they were filtered out as well

Reply 129

Lelanor

14

Original post by aaliya23

did the concordat question say pick three numbers?

It didn't say how many to tick

Reply 130

Sweisman

I worked out the wrong answer for the 2.75 question. I accidentally worked out 7.5( the weight of one of the other compounds) 😞😞

Reply 131

tmg1999

10

for the methyl orange thing
- it definitely CAN'T be orange as methyl orange is actually yellow when neutral (yellow above ph 4.4)

so its either yellow or red...

Reply 132

Abodee1

2

Original post by Castro300

Oh no, i put increase rate AND start reaction. Im guessing the ignore cancels out the accept. But is that for reject though, and not ignore

No dont worry :smile:

you will get the mark they are going to totally ignore the start reaction ignore means consider it as if it wasnot there.

Reply 133

rcmack

OP

9

any other questions??

Reply 134

elertopo

what did you guys for the chemical equation about nitric acid and copper oxide?

Reply 135

Nurne

2

Original post by Niclewis

i have no idea what you are going on about. You are talking down to people like they have no idea. They will accept red because it does turn slightly acidic FACT