Chemistry: Post your doubts here!

[teachyourself]

hi all, can somebody help me, i am looking for a revision book for ATP o level chemistry sylab:5070, thanks

https://www.youtube.com/channel/UCTgPevMIji1ZyP4IPhmwDsQ
https://www.youtube.com/user/MrChuaTungKian
https://www.youtube.com/results?search_query=test+for+anions
https://www.youtube.com/results?search_query=Tests+for+aqueous+cations
https://www.youtube.com/results?search_query=Tests+for+gases
https://www.4shared.com/office/vgquggcX/Study_Quide_0620.html

 

[Need A*]

For All to use

 

[drowning-in-studies]

How do you find the conc of Ca2+ and Mg2+?

 

[drowning-in-studies]

(ii) The partition coeffi cient of a particular pesticide between hexane and water is 6.0.
A solution contains 0.0042 g of the pesticide dissolved in 25 cm3 of water. The solution is
shaken with 25 cm3 of hexane.
Calculate the mass of pesticide that will be dissolved in the hexane layer at equilibrium
Ans is 0.0036g

 

[drowning-in-studies]

How do we know where the Br attaches in 4 (b) (ii)?

 

[drowning-in-studies]

Why is [Fe3+(aq)] = 0.2 mol dm–3 in (d)?
And can you explain (c) (iii)?

 

[krishnapatelzz]

View attachment 61695 View attachment 61696
How do you find the conc of Ca2+ and Mg2+?

this is the paper which i gave exam of i have solved it i will post the reply in 5 min

 

[krishnapatelzz]

View attachment 61695 View attachment 61696
How do you find the conc of Ca2+ and Mg2+?

 

[krishnapatelzz]

View attachment 61695 View attachment 61696
How do you find the conc of Ca2+ and Mg2+?

 

[drowning-in-studies]

How does the moles of Ca2+ equal to the mole of H2Y2–? Isn't the ratio from the equation 1:2?

 

[krishnapatelzz]

How does the moles of Ca2+ equal to the mole of H2Y2–? Isn't the ratio from the equation 1:2?

not for that , because y2- ion has charge 2- and so needs only one ca2+ . note - mg2+ was removed by precipitating so only ca2+ is left .

 

[drowning-in-studies]

not for that , because y2- ion has charge 2- and so needs only one ca2+ . note - mg2+ was removed by precipitating so only ca2+ is left .

ahh ok thanks

 

[HarshuOP]

Could anyone do 9701/52/MJ/15 Q2 part d part 1? Mass of HX. How to ? Thanks

 

[teachyourself]

Can some tell me where to find past papers related to organic chemistry As level 9701

buy a topical past paper book if it is available

or download from here
http://www.gceguide.com/topical-past-papers/

 

[student2]

Cn any1 pls tell me if group 4 is removed frm da syllabus? (Ge/Sn/Pb etc)

 

[teachyourself]

Cn any1 pls tell me if group 4 is removed frm da syllabus? (Ge/Sn/Pb etc)

check the syllabus

 

[krishnapatelzz]

Cn any1 pls tell me if group 4 is removed frm da syllabus? (Ge/Sn/Pb etc)

yea it is removed/ it is not there in 2017 http://www.cie.org.uk/images/164502-2016-2018-syllabus.pdf check out the new syllabus .

 

[3abder7man]

Salam everyone

Can anyone please explain why the answer is A?

 

[DragonCub]

Salam everyone

Can anyone please explain why the answer is A?

Use Le Chatelier's Principle for this question.

Le Chatelier's Principle dictates the equilibrium position to shift to one side (product or reactant), in order to counter any effect from changes in state (temperature, pressure, etc.).
In this case, the "state" that has changes is the pressure, which decreases.
Therefore, the equilibrium position needs to go in a direction that tends to raise the pressure back up. So which direction will it go?

Looking at the equation, we can see that 2 mol of reactant turns into 1 mol of product - there is a general decrease in molar amount along the reaction.
This means the forward reaction acts to lower the system's pressure, thus the backward raises it up.

Therefore, the equilibrium position shall shift towards the reactant side, and will make the mixture even more dark brown.
However, the initial state is already dark brown, so there is no visible change.

 

[Bhaijan]

Please explain Question 5(b), Is this a Ligand exchange reaction?