A mass of 0.4113 g of an unknown acid, HA, is titrated with NaOH. If the acid reacts with 28.10 mL of 0.1055 M NaOH, what is the molar mass of the acid?
Answer is 138.7 g/mol
mols NaOH = M x L = ?
Since this is a monoprotic acid, mols NaOH = mols HA.
mols HA = grams/molar mass
You know mols and grams, solve for molar mass
To find the molar mass of the acid HA, we need to use the information provided in the question.
Step 1: Calculate the amount of NaOH used.
The volume of NaOH used is 28.10 mL, which can be converted to liters by dividing by 1000: 28.10 mL / 1000 = 0.02810 L.
Using the formula: amount (mol) = concentration (mol/L) × volume (L), we can calculate the amount of NaOH used: amount of NaOH (mol) = 0.1055 M × 0.02810 L = 0.00296505 mol.
Step 2: Determine the stoichiometric ratio between NaOH and HA.
From the balanced chemical equation for the reaction between NaOH and HA, we need to determine the stoichiometric ratio between the two.
Assuming the reaction is 1:1, meaning one mole of HA reacts with one mole of NaOH, the amount of HA (in moles) will also be 0.00296505 mol.
Step 3: Calculate the molar mass of HA.
The molar mass of HA can be calculated by dividing the mass of HA by the amount of HA (in moles).
Mass of HA = 0.4113 g.
Molar mass of HA = Mass of HA (g) / Amount of HA (mol) = 0.4113 g / 0.00296505 mol = 138.7 g/mol.
Therefore, the molar mass of the acid HA is 138.7 g/mol.
To find the molar mass of the unknown acid (HA), we need to use the stoichiometry of the reaction.
First, we need to determine the number of moles of NaOH used in the titration.
Given:
Volume of NaOH used (V) = 28.10 mL = 0.02810 L
Concentration of NaOH (C) = 0.1055 M
Using the formula:
Number of moles (n) = Concentration (C) x Volume (V)
n(NaOH) = 0.1055 M x 0.02810 L = 0.002964 mol (rounded to 4 decimal places)
Next, we need to find the moles of HA that reacted with the NaOH.
In a neutralization reaction between an acid (HA) and a base (NaOH), the stoichiometry is 1:1. This means that 1 mole of acid reacts with 1 mole of base.
Since the moles of NaOH used represents the moles of HA that reacted, we have:
n(HA) = 0.002964 mol
Finally, we can calculate the molar mass of the acid (HA) using its mass (m) and moles (n).
Given mass of HA (m) = 0.4113 g
n(HA) = 0.002964 mol
The molar mass (M) is calculated using the formula:
Molar mass (M) = Mass (m) / moles (n)
M(HA) = 0.4113 g / 0.002964 mol
M(HA) ≈ 138.62 g/mol (rounded to 2 decimal places)
Therefore, the molar mass of the unknown acid (HA) is approximately 138.62 g/mol.