I got this answer from someone else but it is off by 4% I can't see why it isn't correct?
This is a tough one, but I am going to try to explain it as best as I can (hope your algebra is good!).
First thing to realize here is that there are 2 equations we have to deal with:
CaBr2 + 2AgNO3 = Ca(NO3)2 + 2AgBr
NaBr + AgNO3 = NaBr + AgBr
For the first equation:
(0.9157-x)g of CaBr2 produces (1.693-y)g of AgBr
For the second equation
x g of NaBr produces y g of AgBr
Notice that g (NaBr + CaBr2) = 0.9157-x +x = 0.9157g (just as the question says)
Also notice that the total g (AgBr) from both equations = 1.693-y+y g = 1.693g.
The key is to solve for x and y (2 equations, 2 unknowns).
Here's how you set it up:
From equation 1:
(0.9157-x)g CaBr2 * 1mole CaBr2/200g CaBr2 * 2mole AgBr/1mole CaBr2 * 188g AgBr/ 1mole AgBr = (1.693-y) g AgBr (1)
From equation 2:
x g (NaBr) * 1mole (NaBr)/103g (NaBr) * 1 mole (AgBr)/ 1mole (NaBr)
* 188g (AgBr)/I mole (AgBr) = y g AgBr (2)
If you break down the 2 equations, you get:
376x - 200y = 5.7 (3)
1.82x = y (4)
if you solve for x and y, you get
x = 0.475g
y = 0.865g
you can confirm this result by plugging in x and y into (1) and (2)
Since we know that x = g NaBr
Therefore g NaBr = 0.475g
% NaBr in the mixture
= 100 * 0.475/0.9157
= 51.87%
Hope this helps
solasoy