The PK_a of a Certain Weak Acid Is 4

question 62

Multiple Choice

The pK_a of a certain weak acid is 4.0. Calculate the ratio of proton acceptor to proton donor at pH 7.0.

• A) 1000:1
• B) 20:1
• C) 3:1
• D) 1:1
• E) The ratio cannot be calculated without knowing the structure of the weak acid.

---

Definitions:

Kiliani-Fischer Chain Lengthening

A chemical reaction that increases the carbon chain length of aldoses by one carbon atom using cyanohydrin formation.

Optical Activity

The ability of a compound to rotate the plane of polarized light, indicating its chiral nature.

Adenosine Monophosphate

A nucleotide composed of an adenine base attached to a ribose sugar and single phosphate group; involved in energy transfer within cells.

Kiliani-Fischer Synthesis

A method for elongating the carbon chain of a monosaccharide, thereby facilitating the synthesis of higher carbohydrates.