Question

The flask contains 10.0 mL of HCl and a few drops of phenolphthalein indicator. The buret contains 0.140 M NaOH. It requires 30.3 mL of the NaOH solution to reach the end point of the titration. What is the initial concentration of HCI?

Answer 1

To find the initial concentration of HCl, calculate the moles of NaOH used in the titration, then use the 1:1 mole ratio between NaOH and HCl to find the moles of HCl, and finally divide by the initial volume of HCl to get the concentration.

Step-by-step explanation:

In order to determine the initial concentration of HCl in a titration experiment using NaOH, we can use the stoichiometry of the neutralization reaction where one mole of HCl reacts with one mole of NaOH. The provided information states that it took 30.3 mL of 0.140 M NaOH to reach the endpoint of the titration.

First, the moles of NaOH used can be calculated:

Moles of NaOH = Volume (L) × Concentration (M) = 0.0303 L × 0.140 M

Since the mole ratio of NaOH to HCl is 1:1, the moles of HCl at the beginning are the same as the moles of NaOH at the end. Now, we can find the concentration of HCl by dividing the moles of HCl by the initial volume of HCl in liters:

Concentration of HCl = Moles of HCl / Volume of HCl (L)

Inserting the known values and performing the calculation will yield the concentration of the HCl solution.