IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE O - Level => Sciences => Topic started by: holtadit on September 04, 2009, 06:34:35 am

Title: Chemistry Help Moles !!! Have been stuck on this one for hours !!! :(
Post by: holtadit on September 04, 2009, 06:34:35 am

Okay the question i need hellp on is in paper 4 oct/nov 2007 GCE-O Level.

Go to question 10 (g).

I understand everything from a-f but i dont understand how they get 0.0131 moles for (g). 0.0131 is given in the mark scheme as the answer.

Please help me !! Please Explain how to do question 10 (g) !!

Title: Re: Chemistry Help Moles !!! Have been stuck on this one for hours !!! :(
Post by: Ghost Of Highbury on September 04, 2009, 01:27:57 pm

okk heres the summary first..

--------------

2NaOH           +          H2SO4  -->  Na2SO4    +   H2O

(26.2 cm3)                (25cm3)
(0.1 mol/dm3)            _____(watever doesnt matter)
0.00262 moles            0.00131 moles
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ok now,
we know that 25 cm3 of acid is 0.00131 moles....
they are just asking what no. of moles will react with 250 cm3..

therefore 25cm3   -   0.00131 moles
             250cm3  -   0.00131 moles * 10 = 0.0131 (ANSWER!!!)

------

some1 plz correct the method if wrong...

Title: Re: Chemistry Help Moles !!! Have been stuck on this one for hours !!! :(
Post by: holtadit on September 14, 2009, 03:43:58 pm

Thanks much obliged. :D

Title: Re: Chemistry Help Moles !!! Have been stuck on this one for hours !!! :(
Post by: Ghost Of Highbury on September 14, 2009, 04:25:01 pm

Quote from: Ari Ben Canan on September 14, 2009, 03:43:58 pm

Thanks much obliged. :D

anytime dude...