Which solution will have a pH of 1?

Introduction

When mixing different volumes of NaOH and HCl of different concentrations, the pH of the resulting solution can vary. In this case, we are looking for the solution that will have a pH of 1 among the given options.

Given solutions:

a. 60 mL M/10 HCl + 40 mL M/10 NaOH
b. 55 mL M/10 HCl + 45 mL M/10 NaOH
c. 75 mL M/5 HCl + 25 mL M/5 NaOH
d. 100 mL M/10 HCl + 100 mL M/10 NaOH

Which solution will have a pH of 1?

The solution that will have a pH of 1 is:

c. 75 mL M/5 HCl + 25 mL M/5 NaOH

Explanation

The solution (c) 75 mL M/5 HCl + 25 mL M/5 NaOH is the solution that ends up with a pH of 1, as it has an excess amount of HCl after complete titration.

The question asks which mixture of NaOH and HCl will result in a solution with a pH of 1. To find this, we have to consider the acidic and basic nature of the constituents. HCl is a strong acid and NaOH is a strong base, and they will neutralize each other on mixing. Thus, the solution that remains acidic (pH=1) would be the one where HCl is present in an excess amount.

Reviewing the provided solutions, option (c) 75 mL M/5 HCl + 25 mL M/5 NaOH meets this condition. In this case, the number of moles of HCl is more than NaOH thus ensuring an excess of HCl even after complete titration. Hence, the pH of this solution would be nearer to the acidic side of the pH scale. Therefore, the solution (c) 75 mL M/5 HCl + 25 mL M/5 NaOH is the correct response.