An unknown diprotic acid (H₂A)requires 31.81 mL of 0.109 M NaOH to completely neutralize a 0.685 g sample.Calculate the approximate molar mass of the acid.

Question

Quizplus · Accepted Answer

First, we need to determine the moles of NaOH used:
0.03181 L x 0.109 mol/L = 0.00347 mol NaOH

Since the acid is diprotic, it will require two moles of NaOH to neutralize one mole of the acid. Therefore, the moles of acid can be calculated as:

0.00347 mol NaOH x (1 mol acid / 2 mol NaOH) = 0.00174 mol acid

To find the molar mass of the acid, we can use the formula:

Molar mass = mass / moles

The mass of the acid is given as 0.685 g, so:

Molar mass = 0.685 g / 0.00174 mol = 394.8 g/mol

Rounding to the nearest whole number gives us an approximate molar mass of 395 g/mol, which corresponds to choice B.

An Unknown Diprotic Acid (H2A)requires 31

An Unknown Diprotic Acid (H₂A)requires 31