Chapter 8.2, Problem 1RQ

Interpretation Introduction

Interpretation :

The products in a reaction between an acid and a base must be explained. How one can tell that a reaction has occurred must also be explained.

Concept Introduction :

An acid and a base react to neutralize each other. Physical and chemical properties are changed when a reaction takes place.

Answer to Problem 1RQ

The products in a reaction between an acid and a base are salt and water.

Explanation of Solution

Let’s consider the reaction between a strong acid (HNO₃) and a strong base (KOH).

  ${\text{HNO}}_{\text{3}}\text{(aq)}\to {\text{H}}^{\text{+}}{\text{(aq)+NO}}_{\text{3}}{}^{\text{-}}\text{(aq)}$ .

From the above equation it can be seen that HNO₃ is completely dissociated to produce H+ and NO₃- ions.

  $\text{KOH(aq)}\to {\text{K}}^{\text{+}}{\text{(aq)+OH}}^{\text{-}}\text{(aq)}$ .

Similarly KOH solution produces K+ and OH- ions.

As these are strong electrolytes so there is complete dissociation. No undissociated molecule can be seen.

Overall reaction will be

  $\begin{array}{l}\text{HCl(aq)+KOH(aq)}\to {\text{KCl(aq)+H}}_{\text{2}}\text{O(l)}\text{.}\\ {\text{H}}^{\text{+}}{\text{(aq)+OH}}^{\text{-}}\text{(aq)}\to {\text{H}}_{\text{2}}\text{O(l)}\text{.}\end{array}$

Thus in the reaction of acid and base one salt and water are produced.

Checking the pH of the solution or using litmus paper it can be understood that a reaction has taken place. As acid makes blue litmus red and base makes red litmus blue so these color will not be observed when acid and base completely neutralizes each other producing salt and water. pH meter can help to measure the pH which is expected to be 7 at 298 K.

Conclusion

Acid and base react to produce salt and water via neutralization reaction. Whether a reaction has taken place can be understood using litmus paper or pH meter.