Question

Let an n-protic acid be an acid that can donate n hydrogen ions and has the formula HnX. If 0.600 L of 0.400 M sodium hydroxide is required to titrate 0.400 L of a 0.300 M HnX to the equivalence point, what is n in HnX?

Answer 1

Answer:

2, the acid is H₂X.

Explanation:

• It is known at equivalence point: the no. of millimoles of base is equal to the no. of millimoles of acid.

∴ (nMV) of NaOH = (nMV) for HnX.

where, n is the no. of producible H⁺ or OH⁻ of the acid or base, respectively.

M is the molarity of the acid or base.

V is the volume of the acid or base.

• For NaOH:

n = 1, M = 0.4 M, V = 0.6 L.

• For HnX:

n = ???, M = 0.3 M, V = 0.4 L.

∴ n for HnX = (nMV) of NaOH / (MV) for HnX = (1)(0.4 M)(0.6 L)/(0.3 M)(0.4 L) = 2.

∴ the acid is H₂X.