Chem-Lab-HELP!!

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

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asked by Macey
  1. 2NaHCO3 + heat ==> Na2CO3 + H2O + CO2

    I would set this up like this.
    Let X = mass NaHCO3
    and Y = mass NaCl
    ======================
    g NaHCO3 + g NaCl = 1.124 and
    g Na2CO3 + g NaCl = 1.124 - 0.270
    ==================================
    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
    =======================
    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.

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