Chemistry: Post your doubts here!

[Brisingr]

Q

Q6 was left so ;
P1V1 + P2V2 = PtVt
Pt , Vt= total pressure and volume
1/1000 *2000 + 2/1000 + 1000 = Pt * 3/1000
Ans = A 1 1/3

can u make me understand what is this formula

 

[Tobaaaaay]

36 When the yellow liquid NCl3 is stirred into aqueous sodium hydroxide, the reaction that occurs
can be represented by the following equation.
2NCl3(l) + 6NaOH(aq) → N2(g) + 3NaCl (aq) + 3NaOCl (aq) + 3H2O(l)
What will be the result of this reaction?
1 The nitrogen is oxidised.
2 A bleaching solution remains after the reaction.
3 The final solution gives a precipitate with acidified silver nitrate.

why is 1) not correct

 

[DeadbeatCIE]

36 When the yellow liquid NCl3 is stirred into aqueous sodium hydroxide, the reaction that occurs
can be represented by the following equation.
2NCl3(l) + 6NaOH(aq) → N2(g) + 3NaCl (aq) + 3NaOCl (aq) + 3H2O(l)
What will be the result of this reaction?
1 The nitrogen is oxidised.
2 A bleaching solution remains after the reaction.
3 The final solution gives a precipitate with acidified silver nitrate.

why is 1) not correct

The ox.no of N in NCl3 is +3 and in N2 it is 0
change in ox.no=3 so N has GAINED 3 electrons so it's been reduced and that's why 1 is not correct and hence C is the right answer

 

[sara_queen]

X is an element in Period 2. In which fluoride is the F–X–F angle the largest?
A BF3 B CF4 C NF3 D OF2

 

[Tobaaaaay]

The ox.no of N in NCl3 is +3 and in N2 it is 0
change in ox.no=3 so N has GAINED 3 electrons so it's been reduced and that's why 1 is not correct and hence C is the right answer

But Nitrogen is more electronegative than chlorine so shouldn't Nitrogen be -3 and Chlorine be +1 (Br<Cl<N<O<F)

 

[SohaibButt]

Why it's not A?

 

[Tobaaaaay]

Why it's not A?

since they are now all liquid. When the bonds in liquid molecules are broken they turn to gas so the best the strength of liquid molecule bond is how easily they turn to gas

 

[Mstudent]

Thankyou but, I know this equation its just that I don't think it's working on that question..( I was getting a wrong answer).

This is how I got it


The quality is pretty bad cuz its my webcam. hope this helps

 

[SohaibButt]

Any trick for this kind of question? :/

 

[amina1300]

This is how I got it
View attachment 62346

The quality is pretty bad cuz its my webcam. hope this helps

OH! Thats how we do It I was a bit confused. Thankss it did help

 

[amina1300]

CAN SOMEONE THIS QUESTION??


ANSWER = B

 

[DeadbeatCIE]

X is an element in Period 2. In which fluoride is the F–X–F angle the largest?
A BF3 B CF4 C NF3 D OF2

BF3 bcos of the electronegative difference

 

[DeadbeatCIE]

But Nitrogen is more electronegative than chlorine so shouldn't Nitrogen be -3 and Chlorine be +1 (Br<Cl<N<O<F)

which year and variant

 

[DeadbeatCIE]

Any trick for this kind of question? :/

I think the answer is C by following the bronsted-lowry theory of acids and bases. HNO2 is stronger than HCO3 so HCO3 acts as a base. HCO3 is carbonic acid which doesn't ionise water as much as HNO2. HCO3 is also a component of blood remember?

 

[amina1300]

http://papers.gceguide.com/A Levels/Chemistry (9701)/9701_w16_qp_13.pdf
Please Explain :
Q 3 ,20, 37 and 16

 

[sara_queen]

BF3 bcos of the electronegative difference

THANK YOU

 

[Holmes]

You just need to understand these:

Pressure is DIRECTLY PROPORTIONAL to Temperature p=nt
Pressure is INDIRECTLY PROPORTIONAL to volume p=n/v where n is a constant

from there you derive the equations 1V1=P2V2, P1/T1 = P2/T2, P1V1/T1 = P2V2/T2

Its pretty simply if you can understand the relationship!!!

hope that helps

thanks

 

[Mstudent]

For ques 16

 

[Holmes]

http://papers.gceguide.com/A Levels/Chemistry (9701)/9701_w16_qp_13.pdf
Please Explain :
Q 3 ,20, 37 and 16

First look at Q 16


Write eq… of decomposition of Mg(NO3)2

2 Mg(NO3)2------------ 2 MgO + 4 NO2 + O2

He wants mass of oxide of Nitrogen ,X

Now find Mr of Mg(NO3)2 i.e = 148.3

Finding moles = 7.4/148.3

= 0.05 moles

Look at the mole ratio of NO2 and Mg(NO3)2 you get

2:4

= 1:2

So moles of NO2 = 0.05*2

= 0.1 moles

To find the mass of NO2 we need MR of NO2 i.e. =46

Finally, Mass = 46*0.1

= 4.6 g

 

[Mstudent]

Someone from here actually told us the trick before

Take the two equations from the data booklet and balance the two equations