Posted by Fai on Friday, November 23, 2012 at 2:41pm.
A 0.682g sample of impure NAHco3 yielded a solid residue consisting of NAc03 and other solid with a mass of 0.467g. What was the mass percent of NAc03 in the sample.
The right 85.4%
Who help

chemistry  DrBob222, Friday, November 23, 2012 at 3:02pm
You have many typos in the problem. Here is the solution with the typos corrected.
Let x = mass NaHCO3
and y = mass of the impurity.

x + y = 0.682
x(molar mass Na2CO3/2*molar mass NaHCO3) + y = 0.467

The above two equations in two unknowns; solve for x = mass NaHCO3.
Then %NaHCO3 = (x/0.682)*100 = 85.4%
Note: I suppose the problem assumes that the impurity is not changed by heating; otherwise it can't be worked.