IGCSE Edexcel Chemistry May 19th 2016

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Reply 20

-Max-

Original post by Spinal tap

I got 0.9g for mass of water I think, and yeah it was reaction 3 because of the ratio

Yeah I put equation 3 as well

Reply 21

sophied24

Original post by Castro300

It wasnt hard, but extremely easy to get tricked like the element found in air, bet people put carbon dioxide when it asked for an element

Oh no I put CO2! I thought it was a bit odd given there were two correct answers but should have gone back to check it! I wasn't sure about the unpolluted air one either? Was H20 an answer or CO2?

Reply 22

Castro300

Original post by Spinal tap

I got 0.9g for mass of water I think, and yeah it was reaction 3 because of the ratio

Yeah, exactly what i got. For dynamic equilibria what 2 things did u put and was backward reaction endothermic

Reply 23

jamesj477

yeah it seemed easy but there were loads of questions to trip you up
element found in air - argon, others were compounds
substance found in unpolluted air - co2 or water vapour (h2o)
what happens when you add 50cm2 of acid to calcium rather than 25cm2 - nothing, it was in excess already
mass of water - 0.9 you had to times by 5
on the graph it was maximum temperature RISE, not just max temp - 10 C
small graph at end - steeper curve that ends at same level as there was same mass
chromatography thing - first blob of solution was at the base line, not the first blob
why you need to wait for gas to cool before measuring - hot gas occupies a larger area, nothing to do with make sure it all reacts.
idk what the right answer for why you rinse the burette with water then solution y, I put
water - to wash out any solution x left in
solution y - to react with any water left in, ensuring a fair test (no idea for that one)

Reply 24

Castro300

Original post by sophied24

Oh no I put CO2! I thought it was a bit odd given there were two correct answers but should have gone back to check it! I wasn't sure about the unpolluted air one either? Was H20 an answer or CO2?

Yeah, i got stuck on the next bit, as it said compound i put co2 cuzz i thought the nitrogen dioxides etc make it polluted

Reply 25

outgoingpopcorn

I put oxygen for the compound one because we learnt in bio that carbon dioxide causes pollution and global warming so I didn't know what to write even though I knew oxygen was not a compound. I was so confused on the question about potassium hydrogencarbonate I just put 2 without giving a reason.

Does anyone know why the temperature didn't change for copper?

Reply 26

-Max-

I'm pretty sure the backward reaction was endothermic because of the temperature change, and endothermic is breaking bonds.

Reply 27

jamesj477

Original post by niv1234

Yeah it's unreactive so it didn't react with the acid.

Reply 28

outgoingpopcorn

Original post by -Max-

Copper's a good conductor of heat and so the surrounding temp didn't rise.

Oh ok thanks

Reply 29

jamesj477

Original post by niv1234

You could have put CO2 or H2O (water vapour)

CO2 - its naturally found in v small quantities due to respiration, decomposition etc.
H2o - evaporation from lakes, transpiration etc.

Reply 30

Spinal tap

Original post by Castro300

Yeah, exactly what i got. For dynamic equilibria what 2 things did u put and was backward reaction endothermic

I put there is a constant amount of product on both sides produced (as in the amount produced doesn't change) and the temperature in the reaction was constant. And yeah backwards reaction was endothermic

Reply 31

jamesj477

Original post by niv1234

Oh ok thanks

no thats wrong, surely if it was a good conductor it would make the surrounding temp rise more...
it didnt react because it is unreactive

Reply 32

Amar Joshi

I missed the graph on the last question, How many marks was that worth?

Reply 33

outgoingpopcorn

Original post by jamesj477

no thats wrong, surely if it was a good conductor it would make the surrounding temp rise more...
it didnt react because it is unreactive

Thats what I was thinking. I wrote down that copper is lower down in the reactivity series than the other metals mentioned.

Reply 34

jamesj477

Original post by niv1234

Thats what I was thinking. I wrote down that copper is lower down in the reactivity series than the other metals mentioned.

Yeah, technically the reason would be that copper is below hydrogen in the reactivity series, so it does not displace it, but you'll get the marks for saying it does not react as it is unreactive I think

Reply 35

username2151383

Original post by Amar Joshi

I missed the graph on the last question, How many marks was that worth?

two

Reply 36

outgoingpopcorn

Original post by jamesj477

That makes so much sense thanks

Reply 37

Lrrgolas

Original post by sophied24

Oh no I put CO2! I thought it was a bit odd given there were two correct answers but should have gone back to check it! I wasn't sure about the unpolluted air one either? Was H20 an answer or CO2?