You weigh out 10.000 g of a mixture of NaHCO3 and Na2CO3 and add an excess of HCl. After the reaction is over, you evaporate off the water and collect the solid, which is found to weigh 9.400 g. How many grams of the original mixture were NaHCO3?

Question

You weigh out 10.000 g of a mixture of NaHCO3 and Na2CO3 and add an excess of HCl. After the reaction is over, you evaporate off the water and collect the solid, which is found to weigh 9.400 g. How many grams of the original mixture were NaHCO3?

Answer 1

NaHCO3 + HCl ==> NaCl + H2O + CO2

Na2CO3 + 2HCl --> 2NaCl + H2O + CO2

Let X = mass NaHCO3
and Y = mass Na2CO3
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Set up two equations and solve them simultaneously.
eqn 1 is mass NaHCO3 + mass Na2CO3=10 g
eqn 2 is mass NaCl from NaHCO3 + mass NaCl from Na2CO3 = 9.400 g.

X + Y = 10.000 g
(molar mass NaCl*X/molar mass NaHCO3) + (2*molar mass NaCl/molar mass Na2CO3) = 9.400

Solve for X.