hich statements regarding the Henderson-Hasselbalch equation are true? If the pH of the solution is known as is the pKa for the acid, the ratio of conjugate base to acid can be determined. At pH = pK a for an acid, [conjugate base] = [acid] in solution. At pH >> pK a for an acid, the acid will be mostly ionized. At pH << pK a for an acid, the acid will be mostly ionized.

First statement is true.

Second statement is true.

Third statement is true.

Explanation:

The Henderson-Hasselbalch equation to determine pH of a buffer is:

pH = pKa + log₁₀ [A⁻] / [HA]

Where A⁻ is the conjugate base of the weak acid, HA

If you know pH and pKa you can solve the rario of conjugate base to acid as follows:

(1)

First statement is true

If pH = pKa:

pH - pKa = log₁₀ [A⁻] / [HA] = 0

1 = [A⁻] / [HA]

[A⁻] = [HA]

Second statement is true.

Based on (1), If pH >> pKa,  [A⁻] / [HA] >>> 1.

That means [A⁻] (The ionized form of the acid), will be present in a higher concentration than [HA]

Third statement is true.

In the same way, If pH <<< pKa, [A⁻] / [HA] <<< 1.

The non-ionized form of the acid, HA, will be present in a higher concentration.

Fourth statment is false

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)