Question

A solution containing 10 mmol of CO₃²⁻ and 5.0 mmol of HCO₃⁻ is titrated with 1.4 MHCl. What volume of HCl must be added to reach the first equivalence point?

Answer 1

To reach the first equivalence point in the titration, 17.86 mL of 1.4 M HCl is required to neutralize 10 mmol of CO₃²⁻ and 5.0 mmol of HCO₃⁻ in the solution.

Step-by-step explanation:

To determine the volume of HCl required to reach the first equivalence point in the titration of a solution containing 10 mmol of CO₃²⁻ and 5.0 mmol of HCO₃⁻, we must take into account that the CO₃²⁻ will react with 2 moles of H+ for each mole of CO₃²⁻, while the HCO₃⁻ will react with 1 mole of H+ per mole of HCO₃⁻.

Therefore, the total moles of H+ needed for the first equivalence point is:

Adding these together gives us 25 mmol of H+ needed. Since the HCl is 1.4 M (which means 1.4 mmol/mL), we can calculate the required volume:

Volume of HCl = moles of H+ / molarity of HCl = 25 mmol / 1.4 mmol/mL = 17.86 mL (rounded to two decimal places).