Chemistry: Post your doubts here!

[madridtas_CR7]

Q = mc(t2 - t1)
Q = 45 * 4.18 * (34.7 - 23.4)
madridtas_CR7

http://pastpapers.papacambridge.com.../Chemistry (9701)/2015 Nov/9701_w15_qp_22.pdf
Q.2 (b)(iii) please explain this question

 

[Thought blocker]

http://pastpapers.papacambridge.com/Cambridge International Examinations (CIE)/AS and A Level/Chemistry (9701)/2015 Nov/9701_w15_qp_22.pdf
Q.2 (b)(iii) please explain this question

http://pastpapers.papacambridge.com/Cambridge International Examinations (CIE)/AS and A Level/Chemistry (9701)/2015 Nov/9701_w15_qp_22.pdf
Q.2 (b)(iii) please explain this question

As it is exothermic reaction sign will be -ve.
And calculation is :
answer of 2b(i) * 10^-3 / 2(bii) = -85.02 kj/mol

 

[selrey]

Element X forms X- ions that can be oxidised to element X by acidified potassium maganate (VII). Ehat could be the values of the first four ionisation energies of X?
A) 418 3070 4600 5860
B) 577 1820 2740 11600
C) 590 1150 4940 6480
D) 1010 1840 2040 4030
Ans is D. Can someone pls explain?

 

[elmansy]

elmansy kp= partial pressure of products^n / partial pressure of reactants^m
partial pressure = total pressure X no.moles of / total number of moles.
pressure = 2atm
partail pressure of N2O4 = 2 X (40/100) = 0.8
partail pressure of NO2 = 2 X (60/100) = 1.2

Kp = 0.8 / (1.2)^2 = 0.56 .

read the book this was a simple question

Many thanks

 

[Thought blocker]

Element X forms X- ions that can be oxidised to element X by acidified potassium maganate (VII). Ehat could be the values of the first four ionisation energies of X?
A) 418 3070 4600 5860
B) 577 1820 2740 11600
C) 590 1150 4940 6480
D) 1010 1840 2040 4030
Ans is D. Can someone pls explain?

A is potasssium
B is Aluminium
C is Calcium
D is Iodine

Group VII can only form X- ions so ansewer is D

 

[nehaoscar]

Here are complete AS and A2 notes for chemistry 9701!
The notes include each and every point of the syllabus

https://www.xtremepapers.com/community/threads/9701-chemistry-notes.43471/

Please like and share if you find them helpful
Check out my signature for more A level notes and revision resources!

 

[Tessa Grey]

I need help. I can't understand these two MCQs. i) Which of the enthalpy changes of the following reactions can only be obtained by Hess's law. 1 The hydration of anhydrous copper sulphate to form crystals of CuSO4.5H2O 2. The formation of methane from its elements 3. The combustion of glucose, C6H12O6 ii) Sodium ions can be formed from sodium atoms. Na(s) ---> Na+(g) Which quantities are required to calculate the enthalpy change of formation of gaseous sodium ions? 1 enthalpy change of atomisation of sodium 2 first ionisation energy of sodium 3 enthalpy change of formation of sodium.

The answer for the first question is C, 2 and 3 are correct.

 

[smiling star]

Can someone explain these two Mcqs please?

 

[Thought blocker]

Can someone explain these two Mcqs please?

which?

 

[i_try9621]

Need help with this

 

[selrey]

View attachment 61502 Need help with this

Ans is D. Since NH4+ ion acts as a proton donor it means NH4Cl is acid and MgOH is basic. So neutralization will occur

 

[i_try9621]

Ans is D. Since NH4+ ion acts as a proton donor it means NH4Cl is acid and MgOH is basic. So neutralization will occur

Thanks

 

[i_try9621]

Need help with this one. Shouldn't the answer be C? ( Ans is B)

 

[DragonCub]

View attachment 61504 Need help with this one. Shouldn't the answer be C? ( Ans is B)

The work and answer are shown in the image.




A simpler way to think is that no matter how much R is generated, the amount of P + Q always stays at 2.
Therefore, the amount of P consumed must equal the amount of Q generated. This means P and Q have the same stoichiometric coefficient.

Again, this leads to Option B.

 

[i_try9621]

The work and answer are shown in the image.

View attachment 61505


A simpler way to think is that no matter how much R is generated, the amount of P + Q always stays at 2.
Therefore, the amount of P consumed must equal the amount of Q generated. This means P and Q have the same stoichiometric coefficient.

Again, this leads to Option B.

Wow you made it look much easier than what I had tried. Thanks!

 

[krishnapatelzz]

Can anyone explain this question and solve?

this is very easy question... 10th grade physics ,,, q = mass x specific heat capacity x change in temperatue

 

[i_try9621]

Need Help ples
It's from 9701/04/O/N/04

 

[Albert Lianto]

View attachment 61520 Need Help ples
It's from 9701/04/O/N/04

Sorry the workings got condensed by the end.

http://imgur.com/gYjLLR2

 

[i_try9621]

Sorry the workings got condensed by the end.

http://imgur.com/gYjLLR2

No problem, I am happy that you helped and I understood it

 

[Need A*]

Inorganic Chem is so HARD !!!!!!!
does any one of u have inorganic notes ??
and I am attaching list of organic reactions ... if any of u need it