HOW WAS CHEMISTRY PAPER 22 ?

[Ansar Khan]

how many grams of zinc ethonate need to be taken for 15 mg of zinc?
ai got something less than 1 i think it was 0.05 or something

It was exactly 0.05

 

[Ansar Khan]

how many grams of zinc ethonate need to be taken for 15 mg of zinc?
ai got something less than 1 i think it was 0.05 or something

How many color changes did u get ?

 

[cowarrior]

whats the value for concentration??.....and can we write ZnO and ZnCl2.?

 

[Idolfanatic95]

Tell me about the first compound. Wasn't it an aldehyde being oxidised into a crboxylic acid?

As far as i understood, The main carbon atom atom already had three methyl groups attached to it, the fourth being -OH. There is no way that it cud be oxidised since:
1) It was a tertiary alcohol
2) Even if you say it cud be, that way C=O wud lead to the formation of FIVE bonds with Carbon which is not possible.

 

[Idolfanatic95]

For equilibrium, it was (0+x)^2 / (0.02-x)^2. And then x was 0.018. What did u guys get?

For equil, it was (2x)^2 / (0.02-x)^2

 

[Idolfanatic95]

whats the value for concentration??.....and can we write ZnO and ZnCl2.?

Concentration for the 1st ques? Im myself doubtful :s
And ZnO im sure is correct. Not sure about zinc chloride.

 

[Idolfanatic95]

It was exactly 0.05

How?

 

[Idolfanatic95]

how many grams of zinc ethonate need to be taken for 15 mg of zinc?
ai got something less than 1 i think it was 0.05 or something

For the conversion of 15mg to grams. it was 15x10^-3, right? Then yes it was 0.05.

 

[cowarrior]

Concentration for the 1st ques? Im myself doubtful :s
And ZnO im sure is correct. Not sure about zinc chloride.

Why not sure about ZnCL2.??

 

[Ansar Khan]

For equil, it was (2x)^2 / (0.02-x)^2

It should be (0+x)^2. How come it's 2x? Initial moles were 0 and final were 0+x. And u had to square it as it was 2HI. Why are you using 2x?

 

[Nishii]

Yep i had only B. But the marks distribution was weird. 10 marks for the tables :O

yeah!

 

[Idolfanatic95]

It should be (0+x)^2. How come it's 2x? Initial moles were 0 and final were 0+x. And u had to square it as it was 2HI. Why are you using 2x?

We had to multiply x with 2 first since there were 2 moles of HI present

 

[Idolfanatic95]

Why not sure about ZnCL2.??

Im hoping Zncl2 is correct cuz i wrote it too. But i dont know. Majority wrote Zinc oxide, zinc hydroxide or zinc carbonate.

 

[Nishii]

How?

i did: (15/65.4) X (219.4) = 50 mg = 0.05g

 

[Idolfanatic95]

Why not sure about ZnCL2.??

It shud be correct though if this reaction does happen. ZnCl2 + H2SO4 -> ZnSO4 + 2HCL

 

[Idolfanatic95]

i did: (15/65.4) X (219.4) = 50 mg = 0.05g

Yeah me too. U think it's right?
What did u get for moles int he next part?

 

[Ansar Khan]

As far as i understood, The main carbon atom atom already had three methyl groups attached to it, the fourth being -OH. There is no way that it cud be oxidised since:
1) It was a tertiary alcohol
2) Even if you say it cud be, that way C=O wud lead to the formation of FIVE bonds with Carbon which is not possible.

See what I remember is there was CHO in the end. It wasn't an alcohol. It was probably (CH3)3CCHO then as a five bond compound would seem rather stupid to give.

 

[Nishii]

whats the value for concentration??.....and can we write ZnO and ZnCl2.?

conc = (0.05/219.4) / (5/1000) = 0.0456 mol/dm3

 

[Idolfanatic95]

See what I remember is there was CHO in the end. It wasn't an alcohol. It was probably (CH3)3CCHO then as a five bond compound would seem rather stupid to give.

I dont seriously remember if it had 2 main carbon chain or 1 :S

 

[Nishii]

Yeah me too. U think it's right?
What did u get for moles int he next part?

yeah..i suppose! conc = (0.05/219.4) / (5/1000) = 0.0456 mol/dm3