Problem: Mixtures of CaCl2 and NaCl are used to melt ice on roads. A dissolved 1.9348-g sample of such a mixture was analyzed by using excess Na2C2O4 to precipitate the Ca2+ as CaC2O4. The CaC2O4 was dissolved in sulfuric acid, and the resulting H2C2O4 was titrated with 37.68 mL of 0.1019 M KMnO4 solution.Calculate the mass percent of CaCl2 in the original sample.

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FREE Expert Solution
  • We have to look for the moles CaClreacted since this will tell how much CaCl2 is in the mixture by stoichiometry
  •  The first step to find it is by reacting Na2C2O4 with CaCl2. Balanced reaction is

Na2C2O(aq)+ CaCl(aq) → CaC2O(s) + 2NaCl (aq)

  • The CaC2O4  produced will further react with H2SO4 (sulfuric acid)

 CaC2O(s) + H2SO4 (aq) → H2C2O(aq) + CaSO(aq)

  • Last reaction was the reaction with KMnO4, be mindful that at this point, solution is still acidic due to presence of acid. This particular reaction will turn oxalic acid (H2C2O4) to two moles of CO2. We will end up with unbalanced equation of:

H2C2O(aq) + MnO4(aq) → 2CO2 (g) +  H2O (l) + Mn2+ (aq)

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Problem Details

Mixtures of CaCl2 and NaCl are used to melt ice on roads. A dissolved 1.9348-g sample of such a mixture was analyzed by using excess Na2C2O4 to precipitate the Ca2+ as CaC2O4. The CaC2O4 was dissolved in sulfuric acid, and the resulting H2C2Owas titrated with 37.68 mL of 0.1019 M KMnO4 solution.

Calculate the mass percent of CaCl2 in the original sample.