Chemistry: Post your doubts here!

[Bhargav Poudel]

2013 O/N Paper 13 Q. 3,14,17,22,28,39. Anybody please?

 

[♣♠ Magnanimous ♣♠]

2013 O/N Paper 13 Q. 3,14,17,22,28,39. Anybody please?

3)You use 10×0.30 = 3 moles of Tl^+ for every 20×0.10 = 2 moles of VO3^-. Every Tl^+ ion loses 2 electrons, so for every equivalent of Tl^+, you get 2(3) = 6 electrons to be taken up by the V atoms.

In VO3^-, V is present as +5. 6 electrons are taken up by 2 equivalents, so 1 equivalent will take up 3 electrons. This leaves you with +5 - 3 = +2.

 

[♣♠ Magnanimous ♣♠]

14)

2013 O/N Paper 13 Q. 3,14,17,22,28,39. Anybody please?

The answer is B. We can get hint as the "chalky" means something related to carbonate and also the carbonates are insoluble so answer is B

 

[♣♠ Magnanimous ♣♠]

2013 O/N Paper 13 Q. 3,14,17,22,28,39. Anybody please?

17) MgO is basic oxides and most metal hydroxides are insoluble, an alkali added to a solution of a metal salt will precipitate an insoluble metal hydroxide. So answer is B

 

[Bhargav Poudel]

1) Umm, you just read the topic "The kinetic theory of gases"(on page 99 of coursebook written by Roger Norris). Do you observe that all points are related to GASES while HCl IS A LIQUID. So it can be clearly said that IT IS THE ONE WHICH MOST DEVIATE FROM IDEAL GAS BEHAVIOUR.
You got na?

HCl can be gas too!?

 

[♣♠ Magnanimous ♣♠]

HCl can be gas too!?

But as HCl is a polar compound it remains as liquid and due to high electronegativity it deviates most from ideal behaviour

 

[qdkhan]

When asked to write about how temperature affects rate, do we mention the Boltzmann theory?
Can we just not write that kinetic energy increases so collision frequency increases?
please mention all d details dis answer should state..

 

[♣♠ Magnanimous ♣♠]

When asked to write about how temperature affects rate, do we mention the Boltzmann theory?
Can we just not write that kinetic energy increases so collision frequency increases?
please mention all d details dis answer should state..

You can write --> As temperature is increased more particles will have energy to react which leads to increases in successful collision between particles resulting in increase in rate of reaction.

 

[The Chill Master]

9) (1)View attachment 49883 here edit 5730 as 5.37 dm3
(2)View attachment 49884 (3)View attachment 49885

dude u shld take voulme in m^3 not dm^3 our tchr told us if u take it in that u get the answer as d

 

[The Chill Master]

Section B
2) Of liquefies --->
Well I don't know the exact reason so I think you should remember it
Sorry in this question I was not able to help you

1 and 2 are correct

 

[fatimarehman]

I want to ask about practicals in practicals then how much time do we actually need to prepare for biology and science practicals as I have practiced practicals for two months only 8 classes. So I am worried as i want to give as exam. My theory and mcqs skills are good. But I have been told that the student who gets B grade in practical gets an overall B in as exam. Is that true?

 

[The Chill Master]

I want to ask about practicals in practicals then how much time do we actually need to prepare for biology and science practicals as I have practiced practicals for two months only 8 classes. So I am worried as i want to give as exam. My theory and mcqs skills are good. But I have been told that the student who gets B grade in practical gets an overall B in as exam. Is that true?

well dont know about bio as well as anything about that grade thingy but i think 8 practicals r less u shld ask for more practise we hv done so far only titration and salt analysis and hv dun it like more than 6 times so we are rele gud at it but if u think u cn give it a shot at pracs and can score gud then it wld be fi9.

 

[♣♠ Magnanimous ♣♠]

dude u shld take voulme in m^3 not dm^3 our tchr told us if u take it in that u get the answer as d

Means overall the calculation was correct.

 

[The Chill Master]

Means overall the calculation was correct.

yep

 

[A*(a*)]

AS level topical MCQs + Theory upto 2014 including ALL variants!

 

[ashcull14]

Ans is B.
Enthalpy change=(Energy given out when bonds are made) - (Energy taken in when bonds are broken)
1800=2X-(994=496)
X=835KJ

SOrry i didnt get this part
How is it 1800?? shudnt it be 180?
n How is 994=496?? its a typing mistake i guess?
can u xplain it again?
1800=2X-(994=496)
X=835KJ

 

[ashcull14]

so is it correct if i do the sum lyk this

n=(120*10^-3)/24
=5*10^-3

(5*10^-3)=0.23/mr
mr=46

(14*1)+(16*2)=46

am i ryt or is there a diff way 2 get it done?

 

[ashcull14]

 

[Asad rehman]

SOrry i didnt get this part
How is it 1800?? shudnt it be 180?
n How is 994=496?? its a typing mistake i guess?
can u xplain it again?
1800=2X-(994=496)
X=835KJ

Sorry it goes:
(N2 +O2)+2(NO)=180
(994+496)-180=2(NO)
=-655KJ
This is energy released when NO bonds formed but in question examiner only asks the energy of NO bond which is given in positive value ie he asks how much u will need for NO bond to break.
Hope u will understand.

 

[janasalem]

During the electrolysis of molten aluminium oxide to produce aluminium, using carbon electrodes,
two consecutive reactions occur at the anode, each producing a different gas.
How does the oxidation number of oxygen change in these reactions?

A decreases by 2, then increases by 2
B increases by 2, then decreases by 2
C increases by 2, then decreases by 4
D no change, then decreases by 2