A student measures 0.2452 g of a monoprotic solid acid, and dissolves the solid in water to make 100.0 mL of solution. the entire solution is titrated to a phenolphthalein endpoint with 45.06mL of 0.1725M KOH.

A. what is the molarity of the acid solution?
B. what is the molar mass of the solid acid?

moles KOH = M KOH x L KOH = ?

moles unknown acid = moles KOH since the acid is monoprotic.
moles acid = grams/molar mass
Solve for molar mass.

To find the molarity of the acid solution, we can use the concept of stoichiometry and the balanced reaction equation between the acid and KOH. The balanced equation for the reaction is:

Acid + KOH -> Water + Salt

From the equation, we can see that the acid and KOH react in a 1:1 ratio. This means that the moles of the acid in the solution are equal to the moles of KOH used in the titration.

To find the moles of KOH used in the titration, we can use the equation:

moles of KOH = volume of KOH (in liters) * molarity of KOH

Given that the volume of KOH used is 45.06 mL (which is 0.04506 L) and the molarity of KOH is 0.1725 M, we can calculate the moles of KOH:

moles of KOH = 0.04506 L * 0.1725 M = 0.00776205 moles

Since the moles of acid and KOH are equal, the moles of acid in the solution is also 0.00776205 moles.

Now, to find the molarity of the acid solution, we need to divide the moles of acid by the volume of the acid solution in liters:

molarity of the acid solution = moles of acid / volume of acid solution (in liters)

The volume of the acid solution is given as 100.0 mL, which is 0.1000 L. Plugging in the values, we get:

molarity of the acid solution = 0.00776205 moles / 0.1000 L = 0.07762 M

Therefore, the molarity of the acid solution is 0.07762 M (or approximately 0.078 M).

To find the molar mass of the solid acid, we need to use the molarity and mass of the acid. The molarity of the acid is 0.07762 M, and the mass of the acid used is 0.2452 g.

We can use the formula:

molarity = moles / volume

To solve for moles, we can rearrange the formula to:

moles = molarity * volume

The moles of acid is equal to the moles of KOH used in the titration, which we previously calculated as 0.00776205 moles.

Now, we can calculate the molar mass of the solid acid by dividing the mass of the acid by the moles of acid:

molar mass = mass of acid / moles of acid

molar mass = 0.2452 g / 0.00776205 moles

Therefore, the molar mass of the solid acid is approximately 31.58 g/mol.