Question

An analytical chemist weighs out 0.218 g of an unknown triprotic acid into a 250 ml volumetric flask and dilutes to the mark with distilled water. she then titrates this solution with 0.0800 m naoh solution. calculate the molar mass of the unknown acid

Answer 1

To calculate the molar mass of the unknown acid, you need to use the equation Moles of acid = Moles of NaOH. Given the volume of the unknown acid solution and the molarity of the NaOH solution, you can calculate the number of moles of NaOH. Since the unknown acid is triprotic, it will react with 3 moles of NaOH for every mole of acid. Divide the mass of the unknown acid by the moles of the unknown acid to calculate the molar mass which will be 10.9 g/mol.

Step-by-step explanation:

To calculate the molar mass of the unknown acid, we need to use the equation:

Moles of acid = Moles of NaOH

Given that the volume of the unknown acid solution is 250 mL, we can convert this to liters by dividing by 1000: 250 mL = 0.250 L. The molarity (M) of the NaOH solution is given as 0.0800 M. Using the equation Molarity = moles/volume, we can calculate the number of moles of NaOH: moles of NaOH = (0.0800 mol/L) x 0.250 L = 0.020 mol NaOH.

Since the unknown acid is triprotic, it will react with 3 moles of NaOH for every mole of acid. Therefore, the number of moles of the unknown acid is also 0.020 mol. To calculate the molar mass, we divide the mass of the unknown acid (0.218 g) by the moles of the unknown acid (0.020 mol): molar mass = mass/moles = 0.218 g / 0.020 mol = 10.9 g/mol.