Question

You are given 5.00 mL of an H2SO4 solution of unknown concentration. You divide the 5.00-mL sample into five 1.00-mL samples and titrate each separately with 0.1000 M NaOH. In each titration, the H2SO4 is completely neutralized. The average volume of NaOH solution used to reach the endpoint is 15.3 mL. What was the concentration of H2SO4 in the 5.00-mL sample

Answer 1

To determine the concentration of H2SO4, the average moles of NaOH used are calculated and then halved to find the moles of H2SO4 reacted, which when divided by the initial volume of H2SO4 in liters, provides the molarity of H2SO4.

Step-by-step explanation:

To find the concentration of the H2SO4 solution, we start by considering the balanced chemical reaction:

H2SO4 (aq) + 2 NaOH (aq) → Na2SO4 (aq) + 2 H2O (l)

It shows that 1 mole of H2SO4 reacts with 2 moles of NaOH.

Given:

Molarity (M) of NaOH = 0.1000

Average volume (V) of NaOH used = 15.3 mL

First, convert the volume in mL to liters:

V = 15.3 mL × (1 L/1000 mL) = 0.0153 L

Now, calculate moles of NaOH used:

moles NaOH = M × V = (0.1000 M) × (0.0153 L)

moles NaOH = 0.00153 mol

From the balanced equation, the moles of H2SO4 will be half:

moles H2SO4 = 0.00153 mol NaOH ÷ 2 = 0.000765 mol H2SO4

Finally, find the concentration by dividing moles of H2SO4 by the volume in L:

Concentration of H2SO4 = moles H2SO4/0.00100 L = 0.000765 mol/0.00100 L

Concentration of H2SO4 = 0.765 M

Answer 2

The concentration of H₂SO₄ = 0.765 M

Step-by-step explanation:

Given: Concentration of NaOH: M₁ = 0.10 M, Volume of NaOH: V₁ = 15.3 mL, Concentration of H₂SO₄: M₂ = ?, Volume of H₂SO₄: V₂ = 1 mL

Reaction involved: H₂SO₄ + 2 NaOH → Na₂SO₄ + 2 H₂O

In this titration reaction, one mole H₂SO₄ neutralizes two moles NaOH.

To find out the concentration of H₂SO₄, we use the equation: N₁ ·V₁ = N₂ ·V₂

Here, N₁, N₂ are the normality of NaOH and H₂SO₄, respectively.

For NaOH: normality: N₁ = M₁

For a diprotic acid like H₂SO₄: normality: N₂ = 2 × M₂

∴ N₁ ·V₁ = N₂ ·V₂

⇒ 0.10 M × 15.3 mL = [2 × M₂] × 1 mL

⇒ M₂ = (0.10 M × 15.3 mL) ÷ (2 × 1 mL) = 0.765 M

Therefore, the concentration of H₂SO₄ = 0.765 M