A 0.125 gram sample if a monoprotic acid of unknown molar mass is dissloved in water and titrated with 0.1003 MNaOH. The endpoint is reached after adding 20.77 ml of base. What is the molar mass of the unknown acid?
for the unknown
moles = mass/RMM
we have the mass, but we need the number of moles to find RMM
so number of moles of NaOH used
is 0.1003 x 20.77/1000
this is the same as the number of moles of the unknown as it is a monoprotic acid.
substitute the number of moles and the mass (0.125 g) in the equation to find RMM
To find the molar mass of the unknown acid, we need to use the information given about the mass of the sample and the volume and concentration of the sodium hydroxide (NaOH) solution.
First, let's calculate the number of moles of NaOH used in the titration:
Number of moles of NaOH = concentration of NaOH × volume of NaOH used
Concentration of NaOH = 0.1003 M
Volume of NaOH used = 20.77 mL = 0.02077 L
Number of moles of NaOH = 0.1003 M × 0.02077 L
= 0.002079 moles
Since the acid and the base react in a 1:1 ratio, the number of moles of the unknown acid is also 0.002079 moles.
Now, we can use the mass of the sample and the number of moles to calculate the molar mass of the acid:
Molar mass of the acid = Mass of the sample / Number of moles
Mass of the sample = 0.125 grams
Number of moles = 0.002079 moles
Molar mass of the acid = 0.125 grams / 0.002079 moles
= 60.02 g/mol
Therefore, the molar mass of the unknown acid is approximately 60.02 g/mol.