Final answer:
To find the equivalent weight of the unknown acid, calculate the moles of NaOH used in the titration and assume a 1:1 mole ratio with the acid. With the number of moles and the given mass of the acid, the equivalent weight is the mass divided by the moles, resulting in 74.56 g/mol.
Step-by-step explanation:
The equivalent weight of an acid is the mass of the acid that would react with one mole of hydroxide ions (OH−). To calculate the equivalent weight of the unknown acid, we must first determine the number of moles of NaOH used in the titration. This can be calculated by multiplying the volume of NaOH (in liters) by its concentration in molarity (moles per liter).
Number of moles of NaOH = (0.01655 L)(0.162 M) = 0.0026809 mol NaOH
Since NaOH and the unknown acid react in a 1:1 mole ratio, we can assume that the moles of NaOH used will equal the moles of the unknown acid. With the number of moles of the unknown acid known and the mass of the acid given, the equivalent weight of the acid can be calculated.
Equivalent weight of acid = Mass of acid / Moles of acid
Equivalent weight of acid = 0.200 g / 0.0026809 mol = 74.56 g/mol