Question

hich statement is true? A. An acid with a large pKa will be a better conductor of electricity than one with a smaller pKa. B. An acid with a large pKa will be less corrosive than one with a smaller pKa. C. An acid with a large Ka will be a poorer conductor of electricity than one with a smaller Ka. D. An acid with a large Ka will be less corrosive than one with a smaller Ka. E. An acid with a large Ka will taste less sour than an acid with a smaller pKa.

Answer 1

Answer:

$\boxed{\text{B is correct}}$

Explanation:

Kₐ and pKₐ are measures of the strength of an acid. For example,

HX + H₂O ⇌ H₃O⁺ + X⁻;  Kₐ = 10¹⁰,  pKₐ = -10

HA + H₂O ⇌ H₃O⁺ + A⁻; Kₐ = 10⁻¹⁰, pKₐ =  10

HX is a strong acid, because it has a larger Kₐ, that is, the position of equilibrium lies far to the right.

However, pKₐ is the negative logarithm of Kₐ, so HX has the smaller pKₐ.

Similarly, Ha is a weak acid, but it has the larger pKₐ.

Strong acid: Large Kₐ ⇔ Low pKₐ

Weak acid:   Small Kₐ ⇔ High pKₐ

A is wrong. HA is a weak acid, so it produces only a few hydronium ions.

B is correct. The rate of corrosion depends on the concentration of hydronium ions. HA is a weak acid, so it is less corrosive than an acid with a small pKₐ.

C is wrong. HX is a strong acid, so there are more ions to carry the current. HX will be a good conductor of electricity.

D is wrong. HX is a strong acid, so it provides more hydronium ions and is more corrosive.

E is wrong. HX is a strong acid, so it provides more hydronium ions to stimulate the taste buds.

$\boxed{\textbf{B is correct}}$