.0900g of unknown acid(diproctic acid) with empirical formular(CHO2) is dissolved in 30.0ml of water and the rest is titrated to the endpoint with 50.0ml of .040 M NaOH(aq) determine the molecular formula of the acid?
H2A + 2NaOH ==> 2H2O + Na2A
The rest of what is titrated? I'm assuming you titrated all of it.
mols NaOH = M x L
mols acid = 1/2 mols of NaOH (look at the coefficients in the balanced equation).
mols acid = grams/molar mass. You know mols and grams, solve for molar mass.
Then (empirical mass)*n = molar mass
Solve for n and round to the nearest whole number. Then (empirical formula)n = molecular formula.
To determine the molecular formula of the unknown acid, we need to calculate the molar mass of the empirical formula (CHO2) and compare it to the molar mass of the unknown acid.
First, let's calculate the molar mass of the empirical formula:
- Carbon (C) has a molar mass of 12.01 g/mol
- Hydrogen (H) has a molar mass of 1.01 g/mol
- Oxygen (O) has a molar mass of 16.00 g/mol
The empirical formula (CHO2) consists of 1 carbon atom, 1 hydrogen atom, and 2 oxygen atoms.
Molar mass of CHO2 = (1 * 12.01 g/mol) + (1 * 1.01 g/mol) + (2 * 16.00 g/mol)
= 12.01 + 1.01 + 32.00
= 45.02 g/mol
Next, let's calculate the number of moles of the unknown acid present in the solution:
Moles of unknown acid = mass of unknown acid (g) / molar mass of unknown acid (g/mol)
Given that the mass of the unknown acid is 0.0900 g and its empirical formula has a molar mass of 45.02 g/mol:
Moles of unknown acid = 0.0900 g / 45.02 g/mol
= 0.0019984 mol
Now, let's use the volume and concentration of the NaOH solution to calculate the number of moles of NaOH used in the titration:
Moles of NaOH = volume of NaOH solution (L) * molarity of NaOH (mol/L)
Given that the volume of NaOH used is 50.0 mL (which is equivalent to 0.0500 L) and the concentration of NaOH is 0.040 M:
Moles of NaOH = 0.0500 L * 0.040 mol/L
= 0.002 mol
From the balanced chemical equation between the acid and NaOH, we know that the ratio of moles of acid to moles of NaOH is 1:1. Therefore, the moles of acid is equal to the moles of NaOH used in the titration.
Since the number of moles of the acid (0.0019984 mol) is very close to the number of moles of NaOH used (0.002 mol), we can conclude that the molecular formula of the acid is the same as the empirical formula (CHO2).
Therefore, the molecular formula of the unknown acid is CHO2.