Back Titration and Chemical Analysis

The video tutorial explains back titrations, an analytical technique used to determine the amount of a reactant by reacting it with an excess of another reactant. The example given involves analyzing an antacid tablet containing calcium carbonate by reacting it with excess hydrochloric acid (HCl). The process includes writing a balanced chemical equation, calculating the amount of HCl and calcium carbonate, and determining the mass percent of calcium carbonate in the tablet. The tutorial concludes with instructions for further study and preparation for a quiz.

What is the primary purpose of a back titration?

• To measure the pH of a solution.

• To find the boiling point of a liquid.

• To determine the concentration of a reactant by using an excess of another reactant.

• To calculate the density of a solid.

In the example of analyzing an antacid tablet, which acid is used in excess?

• Sulfuric acid

• Hydrochloric acid

• Nitric acid

• Acetic acid

What is the balanced chemical equation for the reaction between HCl and calcium carbonate?

• HCl + CaCO3 → CaCl2 + CO2

• 2HCl + CaCO3 → CaCl2 + H2O + CO2

• 2HCl + CaCO3 → CaCl2 + H2O

• HCl + CaCO3 → CaCl2 + H2O + CO2

How many millimoles of HCl are initially used in the reaction with the antacid tablet?

• 100 millimoles

• 25 millimoles

• 75 millimoles

• 50 millimoles

What is the molarity of the NaOH solution used to determine the excess HCl?

• 0.5 M

• 0.1 M

• 0.05 M

• 0.2 M

How many millimoles of calcium carbonate are found in the original tablet sample?

• 11.36 millimoles

• 45.46 millimoles

• 33.45 millimoles

• 22.73 millimoles

What is the molar mass of calcium carbonate used in the calculations?

• 50.05 g/mol

• 100.09 g/mol

• 150.14 g/mol

• 200.18 g/mol

What percentage of the antacid tablet is calcium carbonate?

• 80%

• 70%

• 60%

• 50%

What is the main advantage of using back titration in this analysis?

• It is more accurate than other methods.

• It allows for the determination of a reactant that is not directly titratable.

• It is faster than direct titration.

• It requires less equipment.

What is the final step in a back titration process?

• Heating the solution to evaporate the solvent.

• Subtracting the excess to find the amount that reacted.

• Calculating the amount of excess reactant.

• Measuring the pH of the solution.