Chemistry: Post your doubts here!

[Thought blocker]

sorry but muje kuch samaj me nahi aya

Ask someone else, I have 109 sums left to solve ._.
I'll tell u tomorrow at school.
not.maria help him out, I have 109 sums of physics left to solve.

 

[not.maria]

where the square come from in ques 11

look at the table

 

[♣♠ Magnanimous ♣♠]

which table!

look at the table

 

[Browny]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s04_qp_1.pdf

Can anyone explain question number 13 ans B, 28 ans D and 35 ans B.

Questions are;
In 13 why can't A be correct.
In 28 why is D correct, I think D is correct as tertiary alcohols don't oxidise.
In 35 I don't get a point.

 

[not.maria]

which table!

this one

also look at my post again.I edited it.
the pics were not uploading

 

[not.maria]

this one
View attachment 44479
also look at my post again.I edited it.
the pics were not uploading

kc =(Product)/(reactant)
=(x)(x)/(1-x)(1-x)

do you get it ?

 

[sadiaali]

Please Q11,I cant understand a word
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w12_qp_12.pdf

 

[♣♠ Magnanimous ♣♠]

kc =(Product)/(reactant)
=(x)(x)/(1-x)(1-x)

do you get it ?

okay!

 

[ZaqZainab]

sorry but muje kuch samaj me nahi aya

hope it makes sense

 

[♣♠ Magnanimous ♣♠]

hope it makes sense

Thank you so much

 

[Hadi Murtaza]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w06_qp_1.pdf
Q1
Q11
Q13 how exactly?
Q14
Q16 doesn't it give white ppt?
Please help

q.1
moles = (V × M)/1000

mole ratio of KOH to CaSO₄ = 2 : 1
moles of KOH = (25 × 0.01)/1000
moles of KOH = 2.5 × 10⁻⁴

hence moles of CaSO₄ = (1/2) × 2.5 × 10⁻⁴ = 1.25 × 10⁻⁴

Concentration of CaSO₄ = (1.25 × 10⁻⁴ × 1000)/50
Concentration of CaSO₄ = 2.5 × 10⁻³ mol/dm³
Answer: A

 

[not.maria]

Please Q11,I cant understand a word
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w12_qp_12.pdf

the examiner report gave a pretty nice explanation:
Some candidates might have found it easier to recognise A as
correct if they had rewritten the equation using familiar substances, for example, CH4(g) →C(g) + 4H(g).
Dividing ΔH by 4 will give a value for the C-H bond energy.

 

[ZaqZainab]

q.1
moles = (V × M)/1000

mole ratio of KOH to CaSO₄ = 2 : 1
moles of KOH = (25 × 0.01)/1000
moles of KOH = 2.5 × 10⁻⁴

hence moles of CaSO₄ = (1/2) × 2.5 × 10⁻⁴ = 1.25 × 10⁻⁴

Concentration of CaSO₄ = (1.25 × 10⁻⁴ × 1000)/50
Concentration of CaSO₄ = 2.5 × 10⁻³ mol/dm³
Answer: A

how did you know the volume for CaSO4 was 1000 dm^3?

 

[Hadi Murtaza]

how did you know the volume for CaSO4 was 1000 dm^3?

dats not da volume, volume is 50 cm³
M = (moles × 1000)/V

 

[ZaqZainab]

dats not da volume, volume is 50 cm³
M = (moles × 1000)/V

Oh okay got it thanks can you help me out with the others

 

[Hadi Murtaza]

i can try, i'll do e z ones first.

 

[Hadi Murtaza]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w06_qp_1.pdf
Q1
Q11
Q13 how exactly?
Q14
Q16 doesn't it give white ppt?
Please help

q.31
.
Oxides of group 1 n group 2 metals r basic, as r most other metal oxides.
Mg salts r white usually.
MgO is ionic so high melting point.
All oxides r insoluble except group 1 oxides, Mg is not group 1 so D part is false

 

[ZaqZainab]

q.31
.
Oxides of group 1 n group 2 metals r basic, as r most other metal oxides.
Mg salts r white usually.
MgO is ionic so high melting point.
All oxides r insoluble except group 1 oxides, Mg is not group 1 so D part is false

opps i didn't know about the last point Thanks again

 

[Hadi Murtaza]

opps i didn't know about the last point Thanks again

I knw, Chem is all ratta

 

[Hadi Murtaza]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w06_qp_1.pdf
Q1
Q11
Q13 how exactly?
Q14
Q16 doesn't it give white ppt?
Please help

Q.16
Adding aquoes nitric acid n silver nitrate will give white ppt. If u den add ammonia, ppt dissolves.
Answer: A