Chemistry: Post your doubts here!

[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

 

[The Sarcastic Retard]

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

propan-2-ol will be oxidised to propanone.
Mr of propan-2-ol = 60
Mr of propanone = 58
moles of propan-2-ol = 0.04mol
1:1 ratio
moles of propaone = 0.0.4mol
mass of propaone = 2.32g
75% of mass was the product = 75% of 2.32g = 1.74g

 

[The Sarcastic Retard]

View attachment 57471
question 6 plz

4H20 + Al4C3 + 4NaOH ----------> 4NaAlO2 + 3CH4

 

[The Sarcastic Retard]

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.

Same goes for pressure right? Increasing pressure increases both forward and backward rate?

 

[awesomaholic101]

4H20 + Al4C3 + 4NaOH ----------> 4NaAlO2 + 3CH4

its an equation we should know? or did u get by balancing?

 

[The Sarcastic Retard]

its an equation we should know? or did u get by balancing?

Balancing.

 

[awesomaholic101]

Balancing.

ohkay so u tried each of the options?