# Chemistry: Post your doubts here!

#### XPFMember

XPRS Moderator
Hi everyone, AsSalamoAlaikum Wr Wb..

To get things organized in a better way, I am making this thread. As othewise, some queries remain unanswered!

So post your CHEMISTRY doubts in this thread. InshaAllah members around will help you.

Any Chemistry related notes and links will be added here in this post. Feel free to provide the links to your notes around the forum, or any other websites!

Chemistry Notes:

http://www.chemguide.co.uk This is the website, which contains almost everything classified according to the syllabus.

Tips for solving chemistry MCQs 9701/01

Chemistry P5 Tips and Notes

Some links & Notes - by 'destined007'

Chemistry worksheets Link shared by hassam

Chemistry Application Booklet: Mistakes and Corrections!

Calculations for A level Chemistry, author E.N. Ramsden third edition ebook download.

Regards,
XPC Staff.

#### XPFMember

XPRS Moderator
Re: All Chemistry help here!! Stuck somewhere? Ask here!

Assalamoalaikum!!

first post updated!

#### hassam

Re: All Chemistry help here!! Stuck somewhere? Ask here!

A 20.0mL sample of 0.200M HBr solution is titrated with 0.200M NaOH solution. Calculate the pH of the
solution after the following volumes of base have been added:
15 mL
ANYBODY ????

#### hassam

Re: All Chemistry help here!! Stuck somewhere? Ask here!

A 35.0mL sample of 0.150M ethanoic acid, is titrated with 0.150M NaOH solution. Calculate the pH
after the following volumes of base have been added: 17.5 mL

#### AAestar

Re: All Chemistry help here!! Stuck somewhere? Ask here!

hassam said:
A 20.0mL sample of 0.200M HBr solution is titrated with 0.200M NaOH solution. Calculate the pH of the
solution after the following volumes of base have been added:
15 mL
ANYBODY ????

I am going to give it a try.

Moles HBr = 0.020 L x 0.200 M =0.0040
Moles NaOH = 0.015 L x 0.200 =0.0030

Moles H+ in excess = 0.0010
Total volume = 0.015 L
Concentration H+ = 0.0010 / 0.015 =0.0667
pH =-log ( 0.06667)
=0.176

#### ching293

Re: All Chemistry help here!! Stuck somewhere? Ask here!

Nov 2007 paper4 question 3, CIE

since Cl2 is more +ve, isnt it suppose to undergo reduction? why is the equation the other way round from what i did

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#### memyself15

Re: All Chemistry help here!! Stuck somewhere? Ask here!

yeah, chlorine should gain electrons since it's E* value is more positive.
lets see what xpf member says

#### XPFMember

XPRS Moderator
Re: All Chemistry help here!! Stuck somewhere? Ask here!

Assalamoalaikum!!

ching293 said:
Nov 2007 paper4 question 3, CIE

since Cl2 is more +ve, isnt it suppose to undergo reduction? why is the equation the other way round from what i did

I'm not sure about this question, but according to what I understand, dichromate is an oxidising agent! So it'll oxidise the CL- ion?! :unknown: does that make sense?

#### yubakkk

Re: All Chemistry help here!! Stuck somewhere? Ask here!

where is the discussion of paper 1 and 2 of chemistry??

#### ching293

Re: All Chemistry help here!! Stuck somewhere? Ask here!

XPFMember said:
Assalamoalaikum!!

ching293 said:
Nov 2007 paper4 question 3, CIE

since Cl2 is more +ve, isnt it suppose to undergo reduction? why is the equation the other way round from what i did

I'm not sure about this question, but according to what I understand, dichromate is an oxidising agent! So it'll oxidise the CL- ion?! :unknown: does that make sense?

thats what my classmate told me too, i am not sure, but i guess i'll stick with it. Thanks!

#### OakMoon!

Re: All Chemistry help here!! Stuck somewhere? Ask here!

yubakkk said:
where is the discussion of paper 1 and 2 of chemistry??

You may discuss them here.

#### princesszahra

Re: All Chemistry help here!! Stuck somewhere? Ask here!

XPFMember said:
Assalamoalaikum!!

ching293 said:
Nov 2007 paper4 question 3, CIE

since Cl2 is more +ve, isnt it suppose to undergo reduction? why is the equation the other way round from what i did

I'm not sure about this question, but according to what I understand, dichromate is an oxidising agent! So it'll oxidise the CL- ion?! :unknown: does that make sense?
Every reaction can proceed in heither direction!!but the probability of each of them is different!! so it can either undergo reduction or oxidation( specific conditions!)

#### XPFMember

XPRS Moderator
Re: All Chemistry help here!! Stuck somewhere? Ask here!

ching293 said:
XPFMember said:
Assalamoalaikum!!

ching293 said:
Nov 2007 paper4 question 3, CIE

since Cl2 is more +ve, isnt it suppose to undergo reduction? why is the equation the other way round from what i did

I'm not sure about this question, but according to what I understand, dichromate is an oxidising agent! So it'll oxidise the CL- ion?! :unknown: does that make sense?

thats what my classmate told me too, i am not sure, but i guess i'll stick with it. Thanks!
I'll check with my teacher again! I was about to ask today but I couldn't remember which year it was in

#### hassam

Re: All Chemistry help here!! Stuck somewhere? Ask here!

explain trend of solubility of group 2 sulphates.....well in anser to this.....we have to write that hydration enthalpy decrese faster than lattice bt i dont undrstnd how

#### Newbie

Re: All Chemistry help here!! Stuck somewhere? Ask here!

These sites might help ... check em

1.Beta-Theta.com Chemistry Section
Notes on a number of topics relevant to AS/A Level Chemistry are included. The notes include a particularly good interactive Periodic Table. There is also access to Homework Help and to a Midnight Café chat-room.

This is a US site intended for first year undergraduates, but much is relevant to AS/A Level Chemistry. Notes, articles and tutorial are included. A number of experiment simulations can be accessed. The compound library is very good.

A lighthearted look at many aspects of Chemistry. There are a lot of links to useful pages written by teachers and students. Not all of this is relevant to AS/A Level, but much is. A wealth of information and a lot of fun.

4.Chemsoc Interactive Periodic Table
A high quality interactive Periodic Table with photographs and information about each element.

#### hassam

Re: All Chemistry help here!! Stuck somewhere? Ask here!

jaldi btao....i calculated bt not confident wid ma anser

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