In a titration, 4.1 g of an acid (HX) requires
32.8 mL of 0.74 M NaOH(aq) for complete
reaction. What is the molar mass of the acid?
Answer in units of g/mol.
.........HX + NaOH ==> NaX + H2O
mols NaOH taken = M x L = ?
mols HX = mols NaOH since 1 mol HX = 1 mol NaOH in the balanced equation.
Then mols HX = grams HX/molar mass HX. You know grams and mols, solve for molar mass.
To find the molar mass of the acid (HX), we need to use the concept of stoichiometry.
In a reaction between an acid and a base, the moles of acid must be equal to the moles of base at the equivalence point.
First, let's find the number of moles of NaOH that reacted:
moles NaOH = volume of NaOH (in L) × concentration of NaOH (in mol/L)
= 32.8 mL × (1 L/1000 mL) × 0.74 mol/L
= 0.0243 mol
Based on the balanced chemical equation, the reaction between HX and NaOH is 1:1. This means that the number of moles of HX is also 0.0243 mol.
Next, we'll use the given mass of HX (4.1 g) to find its molar mass.
molar mass = mass of HX (in g) ÷ moles of HX
= 4.1 g ÷ 0.0243 mol
≈ 168.72 g/mol
Therefore, the molar mass of the acid HX is approximately 168.72 g/mol.