The molar mass of an organic acid was determined by the following study of its barium salt. 4.290 g of the salt were
to be converted to the free acid by reaction with 21.64 mL of 0.477 M H2SO4. The barium salt was known to contain
2 moles water of hydration per mol Ba2+, and the acid was known to be monoprotic. What is the molar mass of the
anhydrous acid?
Call the organic acid Hox. Then the barium salt will be Ba(ox)2 and since it is a dihydate it will be Ba(ox)2*2H2O.
Ba(ox)2*2H2O + H2SO4 ==> BaSO4 + 2Hox + 2H2O.
mols H2SO4 = M x L = ?
Convert to mols Ba(ox)2*2H2O. That is 1:1 so you have mols
Ba(0x)2*2H2O = mols H2SO4.
Then mols = grams/molar mass. You know grams and mols, solve for molar mass.
Subtract molar mass 2 mols H2O to get molar mass Ba(ox)2.
Subtract atomic mass Ba to get molar mass [(ox)]^2- and add 2*atomic mass H to get 2 mols of the free acid Hox. Divide by 2 to get molar mass of Hox. I did a quick estimate and I think it's approx 120. My guess, although the problem doesn't ask for it, is Hox is benzoic acid. C6H5COOH = molar mass 122. Post your work if you have additional questions.
Thanks a lot for your soln
To find the molar mass of the anhydrous acid, we need to follow a series of steps:
Step 1: Calculate the number of moles of barium salt.
To do this, we need to determine the number of moles of barium (Ba2+) in the salt. Since the salt contains 2 moles of water of hydration per mole of Ba2+, we need to first find the number of moles of water in the salt.
Given: Mass of the salt = 4.290 g
From the periodic table, the molar mass of water (H2O) is approximately 18.015 g/mol.
Number of moles of water = Mass of water / Molar mass of water
Number of moles of water = (2 moles of water/mol Ba2+) x (18.015 g/mol) x (4.290 g / molar mass of the salt)
Step 2: Calculate the number of moles of H2SO4 used.
Given: Volume of H2SO4 used = 21.64 mL
Concentration of H2SO4 = 0.477 M (moles/L)
Number of moles of H2SO4 used = Concentration of H2SO4 x Volume of H2SO4 used
Number of moles of H2SO4 used = 0.477 mol/L x (21.64 mL / 1000 mL)
Step 3: Calculate the number of moles of acid formed.
Since the acid is known to be monoprotic, the number of moles of acid formed is equal to the number of moles of H2SO4 used.
Number of moles of acid formed = Number of moles of H2SO4 used (calculated in Step 2)
Step 4: Calculate the molar mass of the anhydrous acid.
Given: Mass of the salt = 4.290 g
Molar mass of the anhydrous acid = Mass of the salt / Number of moles of acid formed (calculated in Step 3)
Now you can substitute the respective values into the equation to find the molar mass of the anhydrous acid.