Question

Heating 1.124g of an unknown NaHCO3-NaCl mixture resulted ina mass loss of 0.270g.

1) Calculate the mass of NaHCO3 present in the original mixture.

2) Calculate the mass percent of NaHCO3 in the uknown mixture

Answer 1

2NaHCO3 + heat ==> Na2CO3 + H2O + CO2

I would set this up like this.
Let X = mass NaHCO3
and Y = mass NaCl
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g NaHCO3 + g NaCl = 1.124 and
g Na2CO3 + g NaCl = 1.124 - 0.270
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X + Y = 1.124
X(1 mol Na2CO3/1 mols NaHCO3) + Y = 0.854
====================================
X + Y = 1.124
X(106/2*84) + Y = 0.854
==========================
X + Y = 1.124
0.631X + Y = 0.854
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Solve these two equation simultaneously for X. That will give you grams NaHCO3. You should look up the molar masses of Na2CO3 and NaHCO3 and use a little more accuracy that my rounded numbers of 106 and 84.
After you find g NaHCO3, then
%NaHCO3 = (mass NaHCO3/mass sample)*100 = ??
My numbers are 0.732 g NaHCO3 for 65.1% which should be close.

Answer 2

thank you