"Published in Newark, California, USA"
A sample containing NaBr and KBr only weighs 253.02 mg. The sample was dissolved in water and treated with excess AgNO3. The precipitate formed was found to weigh 429.85 mg. Calculate the %NaBr in the sample.
Solution:
If the solution of the mixture of NaBr and KBr is treated with AgNO3, then AgBr yellow crystal will be formed which is insoluble in water. The chemical reaction for the formation of AgBr is written as follows
If the word statement says "A sample containing NaBr and KBr only weighs 253.02 mg", then the first working equation is
where x is the weight of NaBr and y is the weight of KBr in the mixture.
By gravimetric analysis, we can calculate the amount of AgBr crystals formed from the mixture of NaBr and KBr using their molecular weights as their factor.
The amount of AgBr formed from NaBr is
The amount of AgBr formed from KBr is
If the word statement says "The precipitate formed was found to weigh 429.85 mg.", then the next working equation is
Let's consider the two working equations as follows
Multiply the first equation by -1.577873 and then add it to the second equation, we have
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Hence, the weight of NaBr in the mixture is 0.123948 grams.
Therefore, the %NaBr in the mixture is
