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Chemistry: Post your doubts here!

Hamnah Zahoor

Hamnah Zahoor

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Haroon Ahmed said:
Can anyone kindly answer the question below(and explain why he/she chose the staement).
Q.Two bulbs R and S, connected by a mercury manometer, are held in a thermostat, as shown. The volume of R is twice that of S. R contains gas, X, at the same pressure as the nitrogen in S.When the temperature is increased, which gases in bulb R would cause the mercury level in the right-hand limb of the manometer to rise? 1. an equilibrium mixture N2F4(g) to 2NF2(g); ∆H positive. (PAST PAPER REFERENCE;M-J/2007/PAPER 1/Q34.)
Click to expand...

I guess here the question is focusing on the number of moles.... Considering that there is one mole of Nitrogen in bulb S than according to this in case where temperature is low equilibrium in reaction 1 will also have one number of moles for reverse reaction is being favoured but when temperature is being increased it will result in forward reaction being favoured and the number of moles of gas being produced increasing thus large number of moles of gas causes the mercury on left hand side to decrease due to increased pressure and right hand side to increase for the number of moles in s are low.For the rest of the options in both cases one mole is being produced thus having no effect on the mercury level.
 
mushu.jr

mushu.jr

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1 Most submarines travel under water using electrical power from batteries. The German
engineer Helmut Walter designed a diesel engine that could be used to propel a submarine
beneath the surface of the sea. Instead of taking air from above the surface of the sea,
Walter’s engine used hydrogen peroxide, H2O2, to provide oxygen for a conventional diesel
engine.
Hydrogen peroxide may be catalytically decomposed to give water and oxygen.
(a) (i) What is meant by the term catalyst?
..................................................................................................................................
..................................................................................................................................
(ii) Construct a balanced equation for the decomposition of H2O2.
............................................................................................................................. [3]
Diesel fuel may be considered to consist of the hydrocarbon C15H32 which reacts completely
with oxygen according to the following equation.
C15H32 + 23O2 → 15CO2 + 16H2O
(b) (i) To which homologous series does C15H32 belong?
................................................
(ii) Use the equation above and your answer to (a)(ii) to calculate the amount, in moles,
of H2O2, that will provide sufficient oxygen for the complete oxidation of one mole
of C15H32.
amount of H2O2 = ................................. mol
How to do the last part
 
Hamnah Zahoor

Hamnah Zahoor

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mushu.jr said:
1 Most submarines travel under water using electrical power from batteries. The German
engineer Helmut Walter designed a diesel engine that could be used to propel a submarine
beneath the surface of the sea. Instead of taking air from above the surface of the sea,
Walter’s engine used hydrogen peroxide, H2O2, to provide oxygen for a conventional diesel
engine.
Hydrogen peroxide may be catalytically decomposed to give water and oxygen.
(a) (i) What is meant by the term catalyst?
..................................................................................................................................
..................................................................................................................................
(ii) Construct a balanced equation for the decomposition of H2O2.
............................................................................................................................. [3]
Diesel fuel may be considered to consist of the hydrocarbon C15H32 which reacts completely
with oxygen according to the following equation.
C15H32 + 23O2 → 15CO2 + 16H2O
(b) (i) To which homologous series does C15H32 belong?
................................................
(ii) Use the equation above and your answer to (a)(ii) to calculate the amount, in moles,
of H2O2, that will provide sufficient oxygen for the complete oxidation of one mole
of C15H32.
amount of H2O2 = ................................. mol
How to do the last part
Click to expand...

First, calculate the number of moles of oxygen
(46*16)/32=23 moles
than place this number of moles equal to number of moles of oxygen produced in reaction 1
For finding the number of moles of H2O2 multiply it by 2
2(23)=46 Moles
 
Raheel616

Raheel616

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Concentrated sulfuric acid behaves as a strong acid when it reacts with water
H2SO4 + aq => H^+ + H2SO4^-
The HSO4^- ion behaves as a weak acid.
H2SO4^-(aq) <=> H^+(aq) + SO4^2-
Which statements are true for 1.0 ml dm^3- sulfuric acid?

1. [H^+(aq)] is high
2. [SO4^2- (aq)] is high
3. [HSO4^-(aq)] = [SO4^2-(aq)]

Please explain the answer and reason? (Only statement 1 is correct)
 
Last edited:
Metanoia

Metanoia

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Raheel616 said:
Concentrated sulfuric acid behaves as a strong acid when it reacts with water
H2SO4 + aq => H^+ + H2SO4^-
The HSO4^- ion behaves as a weak acid.
H2SO4^-(aq) <=> H^+(aq) + SO4^2-
Which statements are true for 1.0 ml dm^3- sulfuric acid?

1. [H^+(aq)] is high
2. [SO4^2- (aq)] is high
3. [HSO4^-(aq)] = [SO4^2-(aq)]

Please explain the answer and reason? (Only statement 1 is correct)
Click to expand...

H2SO4 + aq => H^+ + H2SO4^-
Due to full dissociation at the first stage, from 1 mole of H2SO4, we will get 1 mole of H+ and 1 mole of HSO4^-

HSO4^-(aq) <=> H^+(aq) + SO4^2-
Due to partial dissociation at the second stage, from 1 mole of HSO4^-, we will get << 1 mole of H+ and << 1 mole of SO4^2-

Therefore
[SO4^2- (aq)] is low
[HSO4^-(aq)] >> [SO4^2-(aq)]
 
F

Fathima Hd

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9701/12/m/j/ 16 ques 14
Answer is D
Please explain the answer
 

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Hamnah Zahoor

Hamnah Zahoor

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Fathima Hd said:
9701/12/m/j/ 16 ques 14
Answer is D
Please explain the answer
Click to expand...

Write a complete balanced equation for the thermal decomposition of Ca(NO3)2
i.e Ca(NO3)2---->CaO+2NO2+0.5O2
As you can see that total volume of gas produced is 2.5 moles thus from previous informations
1 mole of CaCO3 producing 1 mole of CO2
0.005----->100cm3
1 mole of Ca(NO3)2 producing 2.5mole of Gas
0.005----->250cm3
thus, D is the answer.
 
Holmes

Holmes

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Can anyonne help me rather guide me on Chemistry P5 . I don't know a single word of it. Kindly provide me some source of preparation of Chemisry P5.
 
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