A 0.225g sample of a weak monoprotic acid requires 37.50 mL of 0.100 M NaOH solution to reach the equivalence point. What is the molar mass of the acid?

HA + NaOH ==> NaA + H2O

moles NaOH added = M x L = ??
moles HA must be the same (see the coefficients in the balanced equation).

moles HA = grams/molar mass
You know moles HA and grams HA, solve for molar mass.

To find the molar mass of the acid, we need to determine the number of moles of the acid first.

Step 1: Calculate the number of moles of NaOH used.
We know the volume and concentration of the NaOH solution used. The equation to calculate the number of moles is:

moles NaOH = volume NaOH (in L) × concentration NaOH (in mol/L)

Converting the volume from mL to L:
volume NaOH = 37.50 mL = 0.03750 L

Using the given concentration:
concentration NaOH = 0.100 mol/L

Plugging in the values:
moles NaOH = 0.03750 L × 0.100 mol/L

Step 2: Calculate the number of moles of the acid.
The acid and the NaOH react in a 1:1 ratio. From the balanced equation, we know that 1 mole of acid reacts with 1 mole of NaOH.

So, the number of moles of the acid is equal to the number of moles of NaOH used.

moles acid = moles NaOH

Step 3: Calculate the molar mass of the acid.
The molar mass is the mass of one mole of a substance. We can calculate it using the formula:

molar mass = mass (in g) / moles

Given that the mass of the acid sample is 0.225 g and the number of moles of the acid is moles acid, we can substitute these values into the formula:

molar mass = 0.225 g / moles acid

Now you can calculate the molar mass by plugging in the value of moles acid from Step 2.