Q166CP - Chemistry: Molecular Nature Of Matter And Change

Question

How would you differentiate between a strong and a weak monoprotic acid from the results of the following procedures? 

(a) Electrical conductivity of an equimolar solution of each acid is measured.

 (b) Equal molarities of each are tested with pH paper. 

(c) Zinc metal is added to solutions of equal concentration

Step-by-Step Solution

Answer

(a) Strong acids have higher electrical conductivity.

(b) Strong acids will have lower pH.

(c) Zinc will react more vigorously in a strong acid solution.

Step 1(a): Differentiate between a strong and a weak monoprotic acid

A solution with a higher electrical conductivity will be the stronger acid. A strong acid dissociates fully. Therefore, they produce more ions and will allow greater electrical conductivity due to the presence of an ion charge.

Hence, strong acids have higher electrical conductivity.

Step 2(b): Differentiate between a strong and a weak monoprotic acid

Similarly, a strong acid will fully dissociate and will produce the same concentration of $\left[{\text{H}}_3{\text{O}}^{+}\right]$ . Weak acids do not dissociate fully so they produce lesser $\left[{\text{H}}_3{\text{O}}^{+}\right]$  than strong acids. Since a pH is measured by the presence of $\left[{\text{H}}_3{\text{O}}^{+}\right]$ in a solution, a solution with a pH will be the stronger acid

Hence, strong acids will have a lower pH.

Step 3(c): Differentiate between a strong and a weak monoprotic acid

Zinc metal reacts with $\left[{\text{H}}_3{\text{O}}^{+}\right]$. Similar with the notion above, a strong acid will fully dissociate and will produce the same concentration of $\left[{\text{H}}_3{\text{O}}^{+}\right]$ . Weak acids do not dissociate fully so they produce lesser $\left[{\text{H}}_3{\text{O}}^{+}\right]$ than a strong acid. When there is an abundant amount of $\left[{\text{H}}_3{\text{O}}^{+}\right]$ in a solution, Zinc metal will also react vigorously in the solution. When there is few amount of $\left[{\text{H}}_3{\text{O}}^{+}\right]$ in a solution, Zinc metal will also not react that vigorously in the solution as compared to the strong acid.