Question

An old container of sodium bicarbonate is found in the back of the warehouse. It looks like a good product and there is no worry about contamination, but the plant manager want to know if he can use it to manufacturer a batch of cookies next week. You decide to test it according to the FCCIII: Following the direction in the FCC, your sample of 2.9861g requires 34.48mL of 1.000N sulfuric acid. Does this product meet the specification as required in the FCC? What do you tell the plant manager? Can he go ahead and use it in his cookie dough?

Answer 1

Ans. Balanced reaction: 2 NaHCO₃(s) +H₂SO₄(aq) -----> Na₂SO₄(aq) + 2H₂O(l) + 2CO₂(g)

# Molarity of H₂SO₄ solution = Normality / 2 = 1.000 /2 = 0.500 M

Moles of H₂SO₄ consumed = Molarity x Volume in liters

                                                = 0.500 M x 0.03448 L

                                                = 0.01724 mol

# According to the stoichiometry of balanced reaction, 1 mol H₂SO₄ neutralizes 2 mol NaHCO₃.

So,

            Moles of NaHCO₃ in sample = 2 x moles of H₂SO₄ consumed

                                                            = 2 x 0.01724 mol

                                                            = 0.03448 mol

Mass of NaHCO₃ in sample = Moles x Molar mass

                                                            = 0.03448 mol x (84.006908 g/mol)

                                                            = 2.8966 g

# % NaHCO₃ in sample = (Actual mass of NaHCO₃ / Mass of sample) x 100

                                                = (2.8966 g / 2.9861 g) x 100

                                                = 97.00 %

# FCC threshold value for NaHCO₃ : Not less than 99.0 % , and not greater than 100.5 %.

Since % NaHCO₃ (97.0%) in given sample is less than the FCC threshold value, the sample can’t be used in cookies dough.