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POST YOUR BIO AND CHEM PAPER 1 DOUBT HERE !!!!

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Rania MD

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here's it
 

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R

Rania MD

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L-Girl said:
1- it's neutral
2- bio or chem?
3- mass of lead oxide decreases as it is reduced and changes into lead, and mass of part y is increased as the hydrogen which passed through part x gained oxygen then passed through the flask.. so it's B
4- zinc oxide reacts with the acid, forming colourless solution. but copper will not react with the acid as it's below hydrogen in the reactivity series, so brown solid, which is the copper, remains. so it's B
5- 22: the litmus paper is changed from red to blue in experiment 1 due to the formation of ammonia, but in 2, neither chlorine nor ammonia is produced, this is because there's no reaction (i guess) between aqueous ammonium chloride and sulphuric acid. so there will be no change in experiment 2 and the answer is D
33: idk
6- idk
Click to expand...
okay thank you anyways, but mind if I ask, for (3)- what's the purpose of the drying agent exactly? Thanks again :)
 
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Evangeline

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can anyone please give me the link to chemistry paper1 from 1995 onwards ? ill be very thankful
 
Rahma Abdelrahman

Rahma Abdelrahman

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This Question is from O-level, 5070 June 2011 Q5:
Chem .png
The mark scheme says B, but shouldn't Calcium ion produce a white ppt. that is insoluble in excess of NaOH?
I believe it should be the ammonium ion as it produces no ppt. but just ammonia gas.
What do you think?
 
L

L-Girl

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Rahma Abdelrahman said:
This Question is from O-level, 5070 June 2011 Q5:
View attachment 12320
The mark scheme says B, but shouldn't Calcium ion produce a white ppt. that is insoluble in excess of NaOH?
I believe it should be the ammonium ion as it produces no ppt. but just ammonia gas.
What do you think?
Click to expand...
i think it's B
because calcium could NOT have been present in the solution as it will form a ppt, which was not seen :D
 
Razo513

Razo513

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Rania MD said:
I have some chemistry questions too, if any of you doesn't mind to answer them I'd be very grateful !
(1)- What is the pH of ethanol?(or an alkanol in general)
(2)-Summer 2002(file attached below)-Q.12
(3)-http://www.xtremepapers.com/papers/CIE/Cambridge%20IGCSE/Chemistry%20(0620)/0620_w03_qp_1.pdf (Q.16)
(4)-http://www.xtremepapers.com/papers/CIE/Cambridge%20IGCSE/Chemistry%20(0620)/0620_w11_qp_11.pdf (Q.19)
(5)-http://www.xtremepapers.com/papers/CIE/Cambridge%20IGCSE/Chemistry%20(0620)/0620_w08_qp_1.pdf (Q.22) AND (Q.33=In this particular question, I am sure that NO2 doesn't form as a result of burning fossil fuels, rather from the really hot temperature inside the car engine which forces nitrogen and oxygen molecules in air to bind strongly. But the answer doesn't follow so, why ?!)
(6)-http://www.xtremepapers.com/papers/CIE/Cambridge%20IGCSE/Chemistry%20(0620)/0620_s11_qp_13.pdf (Q.35= I really don't get this one)
Thanks in advance to all who will help ( : ( :
Click to expand...

1) The pH of pure ethanol and all other alcohols is 7, because the pH refers to the number of OH- or H+ ions in a solution, neither are present in any alcohols.




2) B
3) PbO2 + 2H2O → Pb + 2H2O in the tube lead(ii)oxide will loose the o2 & Pb will remain in tube mass decrease drying agent absorbs the water increasing in mass the answer is B
4) Firstly Zn becomes ZnO the alloy has also Cu .. Cu cant react with H2SO4 cuz it cant displace the hydrogen (less reactive) so ZnO + H2SO4 à ZnSO4 + H2O water is the colorless solution & zincsulfide is the brown solid answer is B
5) Q22: as previous explanation
Q33: fossil fuels are made from dead organic matter this matter can be plants ..plants contain nitrogen compounds when u burn the fossil fuels which may include dead plants NO2 if given off

6) Very simple with no complications: they gave u 2 statements
Statement 1: Alloying iron with other materials to form stainless steel prevents iron from rusting
by excluding oxygen.
Statement 2: Painting, oiling and electroplating are all methods of preventing iron from rusting.

The first statement is 100% WRONG because oxygen is not excluded the oxygen concentration in the surrounding is not even controlled to make an alloy . simply alloying is when 2 or more metals are mixed to make this metal mixture stronger & last a little bit longer BUT EVENTUALLY THIS ALLOY IS GOING TO RUST BY TIME the second statement is correct and therefore the answer is D

 
сᴏᴏʟ сяуѕтᴀʟѕ

сᴏᴏʟ сяуѕтᴀʟѕ

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FATIMAH said:
View attachment 12321 CAN ANYONE PLZ EXPLAIN ME THAT HOW WE WILL WORKOUT THE ANSWER ???
Click to expand...
Assalam-o-alaikum wr wb...
the question says that the graph is for a 'single' heartbeat...so we can conclude that it takes 0.6 seconds for one heartbeat...to get the number of heartbeats in 60 seconds (1 minute) we will divide 60 by 0.6 that is equal to 100 heartbeats..!
hope that clears your doubt :)
 
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