Question

Sodium hydrogen sulfate is used as a cleaning agent and as a flux (a substance that promotes the fusing of metals and prevents the formation of oxides). One of the ways in which sodium hydrogen sulfate is manufactured is by reacting sodium dichromate, Na2Cr2O7, with sulfuric acid. This process also forms water and chromium(VI) oxide, CrO3.

a. Write a balanced equation for this reaction. (You do not need to include states.)

b. How many kilograms of chromium(VI) oxide are formed when 130.4 kg of sodium hydrogen sulfate is made?

c. What is the maximum mass of sodium hydrogen sulfate, NaHSO4, that can be formed from the reaction of 874.0 kg of sodium dichromate with 400.0 L of 18.0 M H2SO4?

Answer 1

a) Na₂Cr₂O₇ + 2 H₂SO₄ ----------------> 2 NaHSO₄ + 2 CrO₃ + H₂O

b) From the above reaction it is clear that Na₂Cr₂O₇ is the limiting reactant, hence
1 mole of Na₂Cr₂O₇ gives 2 moles of NaHSO₄
1 mole of Na₂Cr₂O₇ gives 2 moles CrO₃
Hence, 130.4 Kg of CrO3 will be formed

c) mol of  Na₂Cr₂O₇ = 874 *10³ gm / 261.97 g/mol = 3336.2598 mol
[Molar mass of Na₂Cr₂O₇ = 261.97 gm/mol]
mol of H₂SO₄ = 18mol/L * 400L = 7200 mol
Therefore Na₂Cr₂O₇ is the limiting reactant
From the stoichiometry,
1 mol of Na₂Cr₂O₇ gives 2 mol of NaHSO₄
  3336.2598 mol gives ? mol of NaHSO₄
cross multiply to get the answer,
3336.2598*2 = 6672.5196 moles of NaHSO₄ are formed
mass of NaHSO4 = 6672.5196 mol *120.06 g/mol = 801102.7032 gms = 801.1027 Kg
[Molar mass of NaHSO₄ = 120.06 g/mol]
Maximum mass of sodium hydrogen sulfate, NaHSO₄, that can be formed from the reaction
of 874.0 kg of Na₂Cr₂O₇ with 400.0 L of 18.0 M H2SO4 is 801.1027 Kg