[MartynYarrow]

I used 10mL of unknown NaCl-NaBr mixture titrate with 0.10M silver nitrate solution.
10.15mL of silver nitrate solution is used.

the conc. of NaCl-NaBr mixture is 8g/dm3

I need to calculate the % composition of the NaCl-NaBr mixture.

I used the following calculation steps but i can't get the ans.

a + b = c..(1), where c is the weight of the mixture used, consisting a gram of NaCl and b gram of NaBr.

c= 8g x 10/1000 = 0.08g

no of moles of Cl react= a/58.44
no of moles of Br react= b/102.9
no of moles of Ag react=(0.1 x 10.15)/1000= total no of moles of Cl and Br react=a/58.44 + b/102.9
therefore, (0.1 x 10.15)/1000=a/58.44 + b/102.9..(2)

values of a and b should easily be found by solving equation (1) and (2), however I am fail to do so.

What's wrong with my calculation?!?!

[Dan]

At first glance, your work looks fine to me. What exactly is going wrong - is the answer you get different from the answer in a book, or are you having trouble solving the simultaneous equations?

[MartynYarrow]

Actually, I have trouble in solving the simultaneous equations,

a + b = 0.08...(1)
(0.1 x 10.15)/1000=a/58.44 + b/102.9..(2)

I found that a or b is -ve.

I think I may set up wrong equations.....are (1) and (2) both correct?

Can anyone help?

[Padfoot]

Actually, I have trouble in solving the simultaneous equations

Perhaps it would help if you converted your fractions to a common denominator.

58.44*102.9 = ?