Question

A solution was made by adding water to 0.250 g of H2Z until the volume totaled 25.00 mL. Subsequent titration required 40.50 mL of 0.100 M sodium hydroxide. Calculate the molar mass of H2Z (in g/mol).
given: H2Z(aq) + 2 NaOH(aq) → Na 2Z(aq) + 2 H2O(ℓ)

Answer 1

Answer:

123 g/mol

Explanation:

Let's consider the neutralization reaction.

H₂Z(aq) + 2 NaOH(aq) → Na₂Z(aq) + 2 H₂O(ℓ)

The moles of NaOH that reacted are:

$40.50 \times 10^{-3} L \times \frac{0.100molNaOH}{1L} =4.05\times 10^{-3} molNaOH$

The molar ratio of H₂Z to NaOH is 1:2. The moles of H₂Z that reacted are:

$4.05\times 10^{-3} molNaOH \times \frac{1molH_{2}Z}{2molNaOH} =2.03\times 10^{-3} molH_{2}Z$

The molar mass of H₂Z is:

$\frac{0.250gH_{2}Z}{2.03\times 10^{-3} molH_{2}Z} =123g/mol$