Chemistry: Post your doubts here!

[Hamnah Zahoor]

So doesn't it if to be C

Answer is C....

 

[Tigercub]

coniine is the major constituent of the poison ‘oil of hemlock’
Connine can be synthesised by reacting ammonia with a dibromo compound, X
Q28
9701/12/mj/12
What is the name of compound ?
A 1,1-dibromo-2-propylcyclopentane
B 1,2-dibromo-2-propylcyclopentane
C 1,4-dibromooctane
D 1,5-dibromooctane
pls help ;/

 

[Tigercub]

In the manufacture of sulfuric acid the reaction 2SO2(g) + O2(g) 2SO3(g) usually takes place at 400 °C and 1 atm pressure. In one industrial plant, it is decided to change the pressure to
20 atm

What will be the consequences of this change
1 increased running costs
2 an increased percentage of sulfur trioxide in the equilibrium mixture
3 the rate of the backward reaction increases

The answer is A which 1,2 and 3 are correct
But how the rate of the backward reaction increases? I thought it should be decreases?

 

[razor8771]

Q-Use of the Data Booklet is relevant to this question. Which sodium compound contains 74.2% by mass of sodium?
A sodium carbonate
B sodium chloride
C sodium hydroxide
D sodium oxide

Anyone?? Answer is D but I can't figure out why :/

 

[Hamnah Zahoor]

Q-Use of the Data Booklet is relevant to this question. Which sodium compound contains 74.2% by mass of sodium?
A sodium carbonate
B sodium chloride
C sodium hydroxide
D sodium oxide

Anyone?? Answer is D but I can't figure out why :/

(23*2)/((23*2)+16)*100=74.2%
In sodium oxide formula is Na2O

 

[razor8771]

(23*2)/((23*2)+16)*100=74.2%
In sodium oxide formula is Na2O

Ohh i understood, tysm

 

[MShaheerUddin]

X is a salt of one of the halogens chlorine, bromine, iodine, or astatine (proton number 85).
The reaction scheme shows a series of reactions using a solution of X as the starting reagent.

X HNO3/ AgNO3 a precipitate excess NH3(aq) colorless solution

excess HNO3

precipiate



What could X be?

A sodium chloride
B sodium bromide
C potassium iodide
D potassium astatide

 

[Hamnah Zahoor]

X is a salt of one of the halogens chlorine, bromine, iodine, or astatine (proton number 85).
The reaction scheme shows a series of reactions using a solution of X as the starting reagent.

X HNO3/ AgNO3 a precipitate excess NH3(aq) colorless solution

excess HNO3

precipiate



What could X be?

A sodium chloride
B sodium bromide
C potassium iodide
D potassium astatide

When x is added to silver nitrate a precipitate is formed which then dissolves in excess ammonia this dissolving shows that it will be a soluble halogen ....which means chloride. This is the main thing to be focused ...on reading the last step you might get confused but in excess of HNO3 it is actually the ammonia in the complex solution of Silver chloride that reacts to form ammonium nitrate and Silver chloride is left as precipitate.

 

[Hinafatima]

Kindly solve these
May June 2017/11 q#20,24

 

[Hamnah Zahoor]

Kindly solve these
May June 2017/11 q#20,24

For question 24

acid catalyst is added when dehydration is being done ....considering the diagram divide it into two parts from the upper oxygen to the lower right branch and similar division on the left side and then draw the structural formula for it will match the compound in part C.

 

[Hinafatima]

got it thanks

 

[Hinafatima]

Thanks, got it, any idea of question 20?

For question 24

acid catalyst is added when dehydration is being done ....considering the diagram divide it into two parts from the upper oxygen to the lower right branch and similar division on the left side and then draw the structural formula for it will match the compound in part C.

 

[Hamnah Zahoor]

Thanks, got it, any idea of question 20?

This is from the examination report
Question 20
The most commonly chosen incorrect answer was C. C, pentan-3-one, would be reduced to pentan-3-ol. This will dehydrate to give cis and trans pent-2-ene; two isomers. B, butanone, would be reduced to butan-2-ol. This will dehydrate to give cis and trans but-2-ene and but-1-ene, three isomers.

Apart from above statement you have to focus on the statement ....Generating one product or mixture of products in case of option A one product is produced, in option B the product produced shows cis-trans isomerism which are in total three thus producing the most isomers..... same goes for the rest of the options.

 

[Hinafatima]

This is from the examination report
Question 20
The most commonly chosen incorrect answer was C. C, pentan-3-one, would be reduced to pentan-3-ol. This will dehydrate to give cis and trans pent-2-ene; two isomers. B, butanone, would be reduced to butan-2-ol. This will dehydrate to give cis and trans but-2-ene and but-1-ene, three isomers.

Apart from above statement you have to focus on the statement ....Generating one product or mixture of products in case of option A one product is produced, in option B the product produced shows cis-trans isomerism which are in total three thus producing the most isomers..... same goes for the rest of the options.

JazakAllah Khairan kaseera
Actually i didn't have the examiner report so couldn't get any clue,thanks once again

 

[Hamnah Zahoor]

JazakAllah Khairan kaseera
Actually i didn't have the examiner report so couldn't get any clue,thanks once again

My pleasure.

 

[feliciablack2000]

Dinitrogen tetroxide dissociates into nitrogen dioxide on heating.
N2O4⇌2NO2
In an experiment the partial pressures of the gases at equilibrium were found to be NO2 , 0.33 atm; N2O4, 0.67 atm
What is the numerical value of Kp at the temperature of the experiment?
A 0.16
B 0.49
C 0.65
D 2.03
If anyone is generous enough to help me solve this question, i would really appreciate it!

 

[Hamnah Zahoor]

Dinitrogen tetroxide dissociates into nitrogen dioxide on heating.
N2O4⇌2NO2
In an experiment the partial pressures of the gases at equilibrium were found to be NO2 , 0.33 atm; N2O4, 0.67 atm
What is the numerical value of Kp at the temperature of the experiment?
A 0.16
B 0.49
C 0.65
D 2.03
If anyone is generous enough to help me solve this question, i would really appreciate it!

Kp=(0.33)^2/0.67=0.16 .....option A

 

[feliciablack2000]

Thankyou so much!

 

[Holmes]

Guys If anyone is struggling with the ORGANIC CHEMISTRY and other topics as well. Try the link below it's very useful. I got A grade just because of the notes provided on this website.
http://www.khizarchemistry.com/book.html

 

[mehran46]

Hi there I am new to this site. Still trying to get familiar with it.
Wanted the reason for the answer of question 9
thanks