Chemistry: Post your doubts here!

[Mathemagical]

How is the answer D?

2 moles of water are formed, and the arrow is pointed in the correct direction, so it is +2 multiplied by the enthalpy of formation of water.

 

[Studydayandnight]

Wouldn't a lower temperature increase the rate of the forward reaction since it's exothermic? So why is it A instead of D??

 

[Studydayandnight]

2 moles of water are formed, and the arrow is pointed in the correct direction, so it is +2 multiplied by the enthalpy of formation of water.

Yeah I get that part but why is it +, why not - ?

 

[Studydayandnight]

Answer is D. Please explain!

 

[Mathemagical]

View attachment 54277
How is 3 correct?

This is similar to the other question above. Increase in pressure will increase both forward and backward rates, but by different amounts. In this case, the forward will be speeded up more than the backward.

 

[Mathemagical]

Yeah I get that part but why is it +, why not - ?

The direction of the arrow points toward the compound, and as the term "formation" suggests, it is the correct direction and thus the sign is +.

 

[Mathemagical]

Answer is D. Please explain!

Treat the dipoles as vectors. The C-Cl bonds are in opposite directions, so they cancel out each other.

 

[Bilal.khan]

help plzz

 

[princess Anu]

The question states that vigorous effervescence occurred, so naturally I would opt for C, because Barium is the most reactive element amongst the other choices.

but isn't it that barium forms the most stable compounds and so they might not decompose on heating under a bunsen burner..through this logic I eliminated C at first

 

[Metanoia]

but isn't it that barium forms the most stable compounds and so they might not decompose on heating under a bunsen burner..through this logic I eliminated C at first

The first reaction is the decomposition of the CaCO3 to CaO and CO2. BaCO3 remains unaffected.

The 2nd reaction is the reaction of the BaCO3 with the acid.

 

[69ermalik007]

Help neede

 

[malk mohamed]

any tips for chemistry AS paper 31 practical

 

[princess Anu]

30 D
21 c
27 D
last one C?

Help needeView attachment 54285 View attachment 54286 View attachment 54287 View attachment 54288

 

[Bilal.khan]

any tips for chemistry AS paper 31 practical

https://www.xtremepapers.com/community/threads/tips-for-chemistry-practicals-p3.11810/

 

[qwertypoiu]

View attachment 54269

This was nicely explained thank you so much for this sir.
Thanks a lot for the help you provide to numerous students here as well

 

[tiki-taka]

How many decimal places should we take for burette readings
Shud it be 24.1 or 24.10??

 

[The Sarcastic Retard]

How many decimal places should we take for burette readings
Shud it be 24.1 or 24.10??

if u take 1st reading to 2dp then next readings should be in 2dp

 

[69ermalik007]

Yes.... princess anu......all the answers are correct.............but can u explain?

 

[Falconwing]

http://maxpapers.com/wp-content/uploads/2012/11/9701_w14_qp_11.pdf

40) A reaction pathway diagram is shown.
energy
extent of reaction
Which reactions would have this profile?
1 (CH3)3CBr + NaOH → (CH3)3COH + NaBr
2 CH3CH2Br + NaOH → CH3CH2OH + NaBr
3 (CH3)3CCH2CH2Cl + 2NH3 → (CH3)3CCH2CH2NH2 + NH4Cl

How does one even do this? Answer is D.

 

[Metanoia]

http://maxpapers.com/wp-content/uploads/2012/11/9701_w14_qp_11.pdf

40) A reaction pathway diagram is shown.
energy
extent of reaction
Which reactions would have this profile?
1 (CH3)3CBr + NaOH → (CH3)3COH + NaBr
2 CH3CH2Br + NaOH → CH3CH2OH + NaBr
3 (CH3)3CCH2CH2Cl + 2NH3 → (CH3)3CCH2CH2NH2 + NH4Cl

How does one even do this? Answer is D.

1 is a tertiary halogenoalkane, it will undergo SN1 reactions,

• the reaction will take place in 2 steps
• the reaction pathway will contain an intermediate state
• Such reaction paths will be a double hump.

2 and 3 are primary halogenoalkanes, they will undergo SN2 reactions,

• the reaction will take place in 1 step
• the reaction pathway will contain an transition state (not an intermediate).
• Such reaction paths will be a single hump.