A student finds that 1.00 g of a monoprotic acid, HA , requires 50.0 ml of 0.100 M KOH to neutralize it. What is the molar mass of the acid?
To find the molar mass of the acid (HA), we need to use the information given about its reaction with KOH.
Let's start by calculating the number of moles of KOH used in the reaction. We can use the formula:
moles of solute = (concentration of solute) × (volume of solution in liters)
Since the given volume of KOH solution is in milliliters, we need to convert it to liters by dividing by 1000:
volume of KOH solution (in liters) = 50.0 ml / 1000 = 0.050 L
Now we can calculate the number of moles of KOH:
moles of KOH = (0.100 M) × (0.050 L) = 0.005 moles
According to the balanced chemical equation, the stoichiometric ratio between KOH and HA is 1:1. This means that 1 mole of HA reacts with 1 mole of KOH.
Since the reaction used 0.005 moles of KOH, we can conclude that it also used 0.005 moles of HA.
Now we can find the molar mass of HA by dividing its mass (1.00 g) by the number of moles (0.005):
molar mass of HA = mass of HA / moles of HA = 1.00 g / 0.005 moles = 200 g/mol
Therefore, the molar mass of the acid HA is 200 g/mol.