An unknown diprotic acid requires 26.66 mL of 0.117 M NaOH to completely neutralize a 0.845 g sample. what is the molar mass of the acid?
Look at the problem with KHP. All of these are essentially the same.
Step 1 is mols standard solution (the one with BOTH M and L)
Step 2. Use the coefficients in the balanced equation to convert mols of what yu have to mols of what you want.
Step 3. Use the definition of M = mols/L
And by the way, you will notice steps 1, 2 and 3 are the same when you do stoichiometry problems.
H2A + 2NaOH ==> Na2A + 2H2O
mols NaOH = M x L = ?
mols H2A = 2x mols NaOH from the coefficients in the balanced equation.
M H2A = mols H2A/L H2A
To find the molar mass of the unknown diprotic acid, we can follow these steps:
Step 1: Calculate the moles of NaOH used in the reaction.
The volume of NaOH used is 26.66 mL, which is equivalent to 0.02666 L.
Using the equation: moles = concentration × volume, we can find the moles of NaOH used.
moles of NaOH = 0.117 M × 0.02666 L = 0.00310542 moles
Step 2: Determine the molar ratio between NaOH and the unknown diprotic acid.
Since NaOH is a strong base and diprotic acids donate two hydrogen ions, the molar ratio between NaOH and the unknown diprotic acid is 1:2.
Step 3: Calculate the moles of the unknown diprotic acid.
Since the molar ratio of NaOH to the acid is 1:2, the moles of the unknown diprotic acid can be determined by multiplying the moles of NaOH by 2.
moles of the unknown diprotic acid = 2 × 0.00310542 moles = 0.00621084 moles
Step 4: Determine the molar mass of the unknown diprotic acid.
The molar mass of the acid is calculated by dividing the mass of the sample by the number of moles.
molar mass = mass / moles
molar mass = 0.845 g / 0.00621084 moles = 136.19 g/mol
Therefore, the molar mass of the unknown diprotic acid is 136.19 g/mol.
To find the molar mass of the unknown diprotic acid, we need to use the information given about the volume and concentration of NaOH used for neutralization, as well as the mass of the acid sample used.
First, let's calculate the number of moles of NaOH used in the neutralization reaction. We can use the following formula:
moles of NaOH = volume of NaOH (in L) × concentration of NaOH (in M)
Converting the volume of NaOH from milliliters (mL) to liters (L):
volume of NaOH = 26.66 mL = 26.66 ÷ 1000 L = 0.02666 L
Substituting the values into the formula:
moles of NaOH = 0.02666 L × 0.117 M = 0.00312 moles
Now, since the diprotic acid reacts with two moles of NaOH per mole of acid, we can determine the number of moles of diprotic acid using the stoichiometry of the reaction.
moles of diprotic acid = 0.00312 moles ÷ 2 = 0.00156 moles
Next, let's calculate the molar mass of the diprotic acid using the formula:
molar mass = mass of acid (in g) ÷ moles of acid
Given that the mass of the acid sample is 0.845 g:
molar mass = 0.845 g ÷ 0.00156 moles = 541.99 g/mol
Therefore, the molar mass of the unknown diprotic acid is approximately 541.99 g/mol.