Chemistry: Post your doubts here!

[qwertypoiu]

Use of the Data Booklet is relevant to this question.
The compound S2O7 is hydrolysed by water to produce sulfuric acid and oxygen only.
Which volume of oxygen, measured at room temperature and pressure, is evolved when 0.352 g
of S2O7 is hydrolysed?
A 12 cm3 B 24 cm3 C 48 cm3 D 96 cm3
answer is b how

S2O7 + 2H2O ----> 2H2SO4 + (1/2)O2

Moles of S2O7 = 0.352g / Mr = 0.001998mol
Moles of O2 evolved = 1/2 * Ans = 0.0009989mol
Volume = 24,000 * Ans = 24

 

[Aishayasin]

A mixture of nitrogen and hydrogen gases, at a temperature of 500 K, was put into an evacuated
vessel of volume 6.0 dm3. The vessel was then sealed.
N2(g) + 3H2(g) 2NH3(g)
The mixture was allowed to reach equilibrium. It was found that 7.2 mol of N2 and 12.0 mol of H2
were present in the equilibrium mixture. The value of the equilibrium constant, Kc, for this
equilibrium is 6.0 × 10–2 at 500 K.
What is the concentration of ammonia present in the equilibrium mixture at 500 K?
A 0.58 mol dm–3
B 0.76 mol dm–3
C 3.5 mol dm–3
D 27 mol dm–3
answer is b

 

[holoholo]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w11_qp_51.pdf
Question 1 c. how can i decide on the amounts of water and potassium nitrate to use ?
Can someone please answer as soon as possible ?

 

[cute97]

A mixture of nitrogen and hydrogen gases, at a temperature of 500 K, was put into an evacuated
vessel of volume 6.0 dm3. The vessel was then sealed.
N2(g) + 3H2(g) 2NH3(g)
The mixture was allowed to reach equilibrium. It was found that 7.2 mol of N2 and 12.0 mol of H2
were present in the equilibrium mixture. The value of the equilibrium constant, Kc, for this
equilibrium is 6.0 × 10–2 at 500 K.
What is the concentration of ammonia present in the equilibrium mixture at 500 K?
A 0.58 mol dm–3
B 0.76 mol dm–3
C 3.5 mol dm–3
D 27 mol dm–3
answer is b

N2(g) + 3H2(g) 2NH3(g)
N2 = 7.2g/6dm3 = 1.2 mol/dm3
H2 = 12g/6dm3 = 2 mol/dm3

Kc= (NH3)^2/((H2)^3*(N2))
6*10^-2= x^2/ (2^3* 1.2)
x=0758=0.76 which is B

 

[Saad the Paki]

Almost all.This one isn't.

Oh, didn't know that, thanks for letting me know

 

[Aishayasin]

Ammonia is made by the Haber process. The reactants are nitrogen and hydrogen.
N2(g) + 3H2(g) 2NH3(g) ΔH –ve
What will increase the rate of the forward reaction?
A adding argon to the mixture but keeping the total volume constant
B decreasing the temperature
C increasing the total pressure by reducing the total volume at constant temperature
D removing ammonia as it is made but keeping the total volume of the mixture the same
the answer is c why not b

 

[cute97]

Ammonia is made by the Haber process. The reactants are nitrogen and hydrogen.
N2(g) + 3H2(g) 2NH3(g) ΔH –ve
What will increase the rate of the forward reaction?
A adding argon to the mixture but keeping the total volume constant
B decreasing the temperature
C increasing the total pressure by reducing the total volume at constant temperature
D removing ammonia as it is made but keeping the total volume of the mixture the same
the answer is c why not b

Decreasing the temperature would lead to an increase in the yield of ammonia and not fasten the rate of reaction, They are asking which one increases the rate of the reaction, so an increase in kinetic energy would increase the rate of reaction with a lower yield (percentage) of ammonia. So its C not B

 

[My Name]

Oh, didn't know that, thanks for letting me know

Welcome

 

[Aishayasin]

can anyone explain q 38 answer is c

 

[Aishayasin]

Flask X contains 5 dm3of helium at 12 kPa pressure and flask Y contains 10 dm3 of neon at 6 kPa pressure.
If the flasks are connected at constant temperature, what is the final pressure?
A 8 kPa B 9 kPa C 10 kPa D 11 kPa
answer is A

 

[sfhn_128]

Flask X contains 5 dm3of helium at 12 kPa pressure and flask Y contains 10 dm3 of neon at 6 kPa pressure.
If the flasks are connected at constant temperature, what is the final pressure?
A 8 kPa B 9 kPa C 10 kPa D 11 kPa
answer is A

use the equation:

P1V1 = P2V2

5 x 12 + 6 x 10 = (10 + 5) x p
p =8

 

[Hamody]

Plz I need help in enthalpy changes

 

[Aishayasin]

can anyone explain q 38 answer is c

i am confused can anyone explain me its organic chemistry question

 

[Aishayasin]

ANSWER IS C how

 

[qwertypoiu]

i am confused can anyone explain me its organic chemistry question

Spoiler: image

First compound will give both A and B as products. So it has two products.
Second compound will give A and C as products, but you must realize these are both equivalent. Therefore, number 2 gives only one product.
Third compound will give B and D as products. However, you must realize that D cannot be possible, since it involves a carbon atom making 5 bonds. Therefore, number 3 also only has one possible product.

 

[Rizwan Javed]

ANSWER IS C howView attachment 60031

The Cl circled red will form a tertiary alcohol after hydrolysis since the alpha carbon, to which this Cl is attached, is attached to 3 other carbon atoms.

The Cl circled blue will form a secondary alcohol.

The -OH ringed black is the only primary alcohol present in this molecule.

The rest of the -OH groups , highlighted yellow represent secondary alcohols.

So if you count the number of secondary alcohols before hydrolysis, it is 4. After hydrolysis this number increases to 5 as nucleophilic substitution of blue-ringed Cl forms a secondary alcohol. There's only 1 tertiary alcohol, produced by the substitution of red-ringed Cl.
And there's only one primary alcohol, which is circled black.

Therefore, the answer is C.

 

[Aishayasin]

how

View attachment 60035
The Cl circled red will form a tertiary alcohol after hydrolysis since the alpha carbon, to which this Cl is attached, is attached to 3 other carbon atoms.

The Cl circled blue will form a secondary alcohol.

The -OH ringed black is the only primary alcohol present in this molecule.

The rest of the -OH groups , highlighted yellow represent secondary alcohols.

So if you count the number of secondary alcohols before hydrolysis, it is 4. After hydrolysis this number increases to 5 as nucleophilic substitution of blue-ringed Cl forms a secondary alcohol. There's only 1 tertiary alcohol, produced by the substitution of red-ringed Cl.
And there's only one primary alcohol, which is circled black.

Therefore, the answer is C.

how do i know which is secondary and tertiary alcohol in this diagram could u explain i get the primary one

 

[Rizwan Javed]

how

how do i know which is secondary and tertiary alcohol in this diagram could u explain i get the primary one

The corners of this skeleton formula are represented by C atoms (I have marked them with blue Cs). You can see that C atoms to which -OH groups which are highlighted are attached, that carbon is attached to 2 other carbon atoms. So these are the secondary alcohols.

 

[The Sarcastic Retard]

2(b) If step 2 is slowest overall then why a b and c = 1? Help me.

 

[qwertypoiu]

View attachment 60037
2(b) If step 2 is slowest overall then why a b and c = 1? Help me.

I think this is the same question I answered here.
Have a look and see if it helps