Chapter 16.2, Problem 7RQ

(a)

Interpretation Introduction

Interpretation: The $pH$ of the solution needs to be determined.

Concept introduction: $pH$ is measure of the acidity or alkalinity of a solution. The pH scale generally varies from 0 to 14.

The equation for $pH$ is given by,

  $pH=-\text{log[}{H}^{+}]$ where, $\text{[}{H}^{+}]=\text{ concentration of hydrogen ion}\text{.}$

Answer to Problem 7RQ

  $pH$ of the solution is 1.82

Explanation of Solution

Since $HN{O}_3$ is strong acid it dissociates completely into the solution.

  $HN{O}_3(aq)\rightleftharpoons H^{+}\left(aq\right)+N{O}_3{}^{-}\left(aq\right)$

Here the concentration of $H^{+}$ is 0.0150 M.

  $\begin{array}{c}pH=-\text{log[0}\text{.0150}]\\ =1.82\end{array}$

(b)

Interpretation Introduction

Interpretation: The $pH$ of the solution needs to be determined.

Concept introduction: $pH$ is a measure of the acidity or alkalinity of a solution. The pH scale generally varies from 0 to 14.

The equation for $pH$ is given by,

  $pH=-\text{log[}{H}^{+}]$ where, $\text{[}{H}^{+}]=\text{ concentration of hydrogen ion}\text{.}$

Answer to Problem 7RQ

  $pH$ of the solution is 1.82

Explanation of Solution

Since $HN{O}_3$ is strong acid it dissociates completely into the solution.

  $HN{O}_3(aq)\rightleftharpoons H^{+}\left(aq\right)+N{O}_3{}^{-}\left(aq\right)$

Here the concentration of $H^{+}$ is 0.0150 M.

  $\begin{array}{c}pH=-\text{log[0}\text{.0150}]\\ =1.82\end{array}$

(c)

Interpretation Introduction

Interpretation: The $pH$ of the solution needs to be determined.

Concept introduction: $pH$ is a measure of the acidity or alkalinity of a solution. The pH scale generally varies from 0 to 14.

The equation for $pH$ is given by,

  $pH=-\text{log[}{H}^{+}]$ where, $\text{[}{H}^{+}]=\text{ concentration of hydrogen ion}\text{.}$

Answer to Problem 7RQ

  $pH$ of the solution is 1.52

Explanation of Solution

Since $HN{O}_3$ is strong acid it dissociates completely into the solution.

  $HN{O}_3(aq)\rightleftharpoons H^{+}\left(aq\right)+N{O}_3{}^{-}\left(aq\right)$

Here the concentration of $H^{+}$ is 0.0300 M.

  $\begin{array}{c}pH=-\text{log[0}\text{.0300}]\\ =1.52\end{array}$

(d)

Interpretation Introduction

Interpretation: The relative $pH$ values in parts a-c above needs to be explained.

Concept introduction: $pH$ is a measure of the acidity or alkalinity of a solution. The pH scale generally varies from 0 to 14.

The equation for $pH$ is given by,

  $pH=-\text{log[}{H}^{+}]$ where, $\text{[}{H}^{+}]=\text{ concentration of hydrogen ion}\text{.}$

Answer to Problem 7RQ

The $pH$ of the solution is only depends on the concentration of strong acid.

Explanation of Solution

  $\text{Concentration}=\frac{\text{moles of solutes}}{\text{volume of the solution}\left(\text{L}\right)}$

Even if you use different volumes keeping the concentration of the solution same $pH$ will not change. This is obvious from the calculation of part a and b.

With increase in the concentration of $H^{+}$ , $pH$ of the solution will decrease which means solution becomes more acidic.