Chemistry: Post your doubts here!

[pikachu]

can anyone tell me how to solve this question?

 

[daredevil]

can anyone tell me how to solve this question?
View attachment 33872

for reaction 1:
Kc = [X2Y]^2 / ( [X2]^2 . [Y2] )

for reaction 2:
Kc = ( [X2] . [Y2]^1/2 ) / [X2Y]

If you look closely u will see that Kc for 2 is reciprocal of underroot of Kc for 1.
The numerator for Kc 1 is the denominator for Kc2 and vice versa.
then power on every substance of Kc1 is twice the power of every substance of Kc 2
so A is the answer as Kc of 2 is the reciprocal of square root of Kc 1.

Tell me if u dont get it

 

[ahmed abdulla]

Bond length of Cl2 is ( 242 ) as stated in data booklet ..
but in marking schemes they CONTINUOUSLY use ( 244 ) !
it happened in more than one year .

 

[hassankhan]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s03_qp_1.pdf
anyone who can help me with Q1

 

[hassankhan]

Most modern cars are fitted with airbags. These work by decomposing sodium azide to liberate
nitrogen gas, which inflates the bag.
2NaN3
3N2 + 2Na
A typical driver’s airbag contains 50 g of sodium azide.
Calculate the volume of nitrogen this will produce at room temperature.

A 9.2 dm3 B 13.9 dm3 C 27.7 dm3 D 72.0 dm3

 

[daredevil]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s03_qp_1.pdf
anyone who can help me with Q1

use molar gas volume to calculate the no of moles of Oxygen.

then multiply this no. of mol with Avogadro's constant to get the number of particles.

 

[daredevil]

Most modern cars are fitted with airbags. These work by decomposing sodium azide to liberate
nitrogen gas, which inflates the bag.
2NaN3
3N2 + 2Na
A typical driver’s airbag contains 50 g of sodium azide.
Calculate the volume of nitrogen this will produce at room temperature.

A 9.2 dm3 B 13.9 dm3 C 27.7 dm3 D 72.0 dm3

calculate the Mr of NAN3 ...
caculate the moles of NaN3 in 50 g of NaN3 by 50/Mr
use the ratio method to calculate the moles of N2 produced
if 2 mole of NaN3 produces 3 moles of N2 then how many moles will (calculated moles) produce?

calculate the volume using the molar gas volume:
moles * 24 = volume of N2

 

[ahmed abdulla]

My new Thread :
With notes + practical tips ect
Have a look { https://www.xtremepapers.com/commun...al-tips-some-important-notes-dont-miss.31108/ }

 

[salvatore]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w09_qp_51.pdf
Could someone please help me with qn no. 2(a) of this paper? To calculate the mass of zinc, why do we have to use (B - D) and not (B - A)?
Thanks

I'm re-posting this.. anyone??

 

[thats_me]

Use of the Data Booklet is relevant to this question.
A student mixed 25 cm3 of 0.10 mol dm–3 sodium hydroxide solution with 25 cm3 of 0.10 mol dm–3
hydrochloric acid and noted a temperature rise of 2.5 °C.
What is the enthalpy change of the reaction per mole of NaOH?
A –209 kJ mol–1
B –104.5 kJ mol–1
C –209 J mol–1
D –522.5 J mol–1

 

[daredevil]

I'm re-posting this.. anyone??

we need to know the amount of zinc that was used. To do that we have to subtract the total zinc from that which remained in excess. Thus B-D
Do you get it?

If we do B-A we will only subtract the weight of empty test tube and that will only give us the mass of zinc we took initially and is not any help.

If there is further problem do ask

 

[salvatore]

we need to know the amount of zinc that was used. To do that we have to subtract the total zinc from that which remained in excess. Thus B-D
Do you get it?

If we do B-A we will only subtract the weight of empty test tube and that will only give us the mass of zinc we took initially and is not any help.

If there is further problem do ask

That makes perfect sense.. dunno why I couldn't think of that.
Thanks mate..

 

[abruzzi]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w07_qp_4.pdf
Someone please help me with question 4b (i & ii). It looks pretty easy but I don't know what to do.
ThankYou

 

[skinnyboyfat]

Somebody explain please
got a test tommorow .....

 

[NaNinG]

well,its not a doubt in particular.
but
http://www.chemguideforcie.co.uk <------------This website,i guess most of us use it,(if u dont,look at it its great)
does ny1 here know where i can get the PDF format or jus word format of the data it contains per topic,cuz copy pasting takes like 4 ever.

 

[mahabaloch]

anyone can help me how to make isomers i always get stuck in that?

 

[hassankhan]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w03_qp_4.pdf
Q4 part c anyone??

 

[abruzzi]

I just can't get my head through this question. Please help me understand how to balance such types of questions.
I'll be grateful for any tips/tricks given.

 

[sweetiepie]

i have compiled all necessary stuff here https://www.xtremepapers.com/community/threads/some-different-notes-website-are-available.10423/ i hope it helps evryone

 

[Abdel Moniem]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w07_qp_1.pdf.
Question 9 please