Chemistry: Post your doubts here!

[The Sarcastic Retard]

Qn 6.
Original Mr (CaCl2) = 111
Final Mr (CaCl2.2H2O) = 147
% Increased in Mr =(36/111) x 100% = 32%

Qn8.
Moles of Cr2O7 2- = 0.00131 mol
Moles of Fe2+ = 0.00131 x 6 = 0.00786 mol
Mass of Fe = 0.00786 x 56 = 0.44 g
% of Fe = (0.44/1) x 100% = 44%

Qn17.
Describing an element that forms an amphoteric oxide, so answer is Al.

Qn 18.
P4O10 + 6H2O --> 4H3PO4

Qn 19.
CO2 is released when HCl is added to CaCO3.

Qn30.
You can post your isomers, and I'll help to see what's missing.

Qn39.
Statement 1: true, hydrazone is orange
Statement 2: false, ethanoic acid is colorless
Statement 3: false, ethan-1,2- diol is colorless.

Qn40.
View attachment 57440

Q30 : Are they correct?
Q39 : statement 2 isnt color changes from orange to green. No?
Q40 : How statement 1 is correct?
THanks.

 

[Metanoia]

Since it's added to the Fe cell the equation would be FeSO4 == Fe^2+ + SO4^2-
So as Na2SO4 is added the concetration of SO4^2- ions increases so the equilibrium shifts to the left??

That is not the correct half equation to use. The equation should be a redox equation.

Fe2+ --> Fe3+ + e-

Adding the Na+ and SO42- ions to the solution does not affect the equilibrium.

For the second step you have done (8.9 x 10^-4 *(0.1)) instead the mark scheme has done (8.9 x 10^-4 *(0.2)) so the pH works out to be 1.87 instead of 2.02
View attachment 57445
So I'm confused how they got 0.2 as concentration :/

I have relooked at the question and spotted my mistake.

The concentration of Fe2(SO4)3 is o.1 mol/dm3. But since we are using concentration of Fe3+ , we do need to multiply it by 2 as there are two Fe3+ ions for each Fe2(SO4)3.

I will be editing my original answer incase it misleads others.

 

[donewithtime80]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w14_qp_12.pdf

hi, please help me solve these questions:
4 - no idea how to go about this
15- i got my answer as 0.2826... why multiply it *100?
28- idk why it's not B
31- V 3+ has 20 electrons and shells are filled... then how are the electrons unpaired ?
37- y c?

answers:

4- A
15- B
28- C
31-A
37- c

Thanks in Advance

 

[Metanoia]

Q30 : Are they correct? View attachment 57448
Q39 : statement 2 isnt color changes from orange to green. No?
Q40 : How statement 1 is correct?
THanks.

Qn 30. A bit hard for me to see your picture. I've attached my solution for you to compare.


Qn 39. The green color is due to the Cr3+ ions, not the organic products.

Qn 40. CN- is a negative ion and is thus a stronger nucleophile than the neutral HCN.

 

[The Sarcastic Retard]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w14_qp_12.pdf

hi, please help me solve these questions:
4 - no idea how to go about this
15- i got my answer as 0.2826... why multiply it *100?
28- idk why it's not B
31- V 3+ has 20 electrons and shells are filled... then how are the electrons unpaired ?
37- y c?

answers:

4- A
15- B
28- C
31-A
37- c

Thanks in Advance

4) 1 * 10^5 * v = 293 (n and R is const.)
v = 2.93 * 10^-3
Now, for whole system, volume is 4v
p * 4(2.93 * 10^-3) = 373
p = A.

15) n = 15 * 10^-3 * 2 = 0.03mol
25 cm^3 ---> 0.03 mol
250 cm^3 = 0.3mol
1 : 1 ratio
0.3 * (39+39+16) = B

28) Organic acid produced is butanoic acid (CH3CH2CH2COOH) C4H8O2 --> C2H4O = C

31) Electron removal is from 4s orbital. 2 electrons removed from that orbital and 1 wil be removed from 3d orbital so one unpaired electron present in 3d.

37) The answer is B not C.

 

[Metanoia]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w14_qp_12.pdf

hi, please help me solve these questions:
4 - no idea how to go about this
15- i got my answer as 0.2826... why multiply it *100?
28- idk why it's not B
31- V 3+ has 20 electrons and shells are filled... then how are the electrons unpaired ?
37- y c?

answers:

4- A
15- B
28- C
31-A
37- c

Thanks in Advance

Qn 4.


Qn 15. Most likely you've overlooked the info that only 25 cm3 out of the 250 cm3 was used for titration.

Qn 28.


Qn 31. You have to write out the configuration of V atom first and then remove electrons from the outer shells.

Qn 37. I have actually explained a similar question (qn 40) in this post
https://www.xtremepapers.com/commun...st-your-doubts-here.9859/page-732#post-942168

 

[The Sarcastic Retard]

Qn 30. A bit hard for me to see your picture. I've attached my solution for you to compare.
View attachment 57449

Qn 39. The green color is due to the Cr3+ ions, not the organic products.

Qn 40. CN- is a negative ion and is thus a stronger nucleophile than the neutral HCN.

Thanks.

 

[donewithtime80]

@Thesarcasticretard Metanoia thanks...

 

[donewithtime80]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w13_qp_12.pdf

questions... 3, 5, 7, 8, 9, 20 please...

20- why isn't it the reduction process?
9- is it okay to use eq.moles to get Kc? how to get NH3 as 1.76?
8- no idea
7- is it due to stability of carbocation or sth?
5-no idea
3- no idea

pls help

TIA

 

[The Sarcastic Retard]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w13_qp_12.pdf

questions... 3, 5, 7, 8, 9, 20 please...

20- why isn't it the reduction process?
9- is it okay to use eq.moles to get Kc? how to get NH3 as 1.76?
8- no idea
7- is it due to stability of carbocation or sth?
5-no idea
3- no idea

pls help

TIA

Here, look at this videos and search on right side for other questions of same paper..

 

[forest822]

 

[krishnapatelzz]

26 Use of the Data Booklet is relevant to this question. 2.40g of propan-2-ol were mixed with excess acidified potassium dichromate(VI). The reaction mixture was then boiled under reflux for twenty minutes. The organic product was then collected by distillation. The yield of product was 75.0%. What mass of product was collected? A 1.74g B 1.80g C 2.22g D 2.32g

 

[krishnapatelzz]

View attachment 57464 View attachment 57465

answer to 29 is
first write the balanced equation
c6h8o7 + 3NAOH gives c6h5o7na3 + 3h2o
then find the mols of 3NAOH that is:- 3x0.005 = 0.015 mol
now we will calculate volume that is equal to mol divided by concentration
0.015/0.4 = 0.0375dm3
0.0375dm3=37.5cm3
hope you understand if any question reply

 

[forest822]

answer to 29 is
first write the balanced equation
c6h8o7 + 3NAOH gives c6h5o7na3 + 3h2o
then find the mols of 3NAOH that is:- 3x0.005 = 0.015 mol
now we will calculate volume that is equal to mol divided by concentration
0.015/0.4 = 0.0375dm3
0.0375dm3=37.5cm3
hope you understand if any question reply

Thanks for the solution. Btw, how do I know how to form C6H5O7Na3 ? I know the calculation part but not this.

 

[krishnapatelzz]

Thanks for the solution. Btw, how do I know how to form C6H5O7Na3 ? I know the calculation part but not this.

see sodium hydroxide reacts with carboxylic acid forming COONA there are 3 COOH group so there will be 3 NA and the 3 hydrogen will come out

 

[SadiaMaryam]

Should not the answer be B. Because as the reaction is exothermic, increasing the temperature will shift the equilibrium towards reactants, and the rate of backward reaction increases.
But answer is A, how?

 

[darks]

View attachment 57468

Should not the answer be B. Because as the reaction is exothermic, increasing the temperature will shift the equilibrium towards reactants, and the rate of backward reaction increases.
But answer is A, how?

it will shift backwards so the "yield" of products on LHS increases.
increasing temperature increases "rates" whether the reaction is exo or endo. And the effect is on both sides.

 

[22shimmer22girly]

hey guyz, i had a question regarding p5 in chem...for a2....other dan notes and past papers...and advice?

 

[awesomaholic101]

question 6 plz

 

[The Sarcastic Retard]

View attachment 57464 View attachment 57465

Q30