Question

To standardize an H2SO4 solution, you put 20.00 mL of it in a flask with a few drops of indicator and put 0.450 M NaOH in a buret. The buret reads 0.63 mL at the start and 44.73 mL at the end point. Find the molarity of the H2SO4 solution. Start by writing a balanced chemical equation for this neutralization reaction. Question 5 options: 0.250 M

Answer 1

To standardize 20.00 mL of 0.495 M H₂SO₄ are used 44.10 mL of 0.450 M NaOH in a neutralization reaction.

We want to standardize a H₂SO₄ solution with NaOH. The neutralization reaction is:

H₂SO₄ + 2 NaOH ⇒ Na₂SO₄ + H₂O

The buret, which contains NaOH, reads initially 0.63 mL, and 44.73 mL at the endpoint. The used volume of NaOH is:

$V = 44.73 mL - 0.63 mL = 44.10 mL$

44.10 mL of 0.450 M NaOH are used for the titration. The reacting moles of NaOH are:

$0.04410 L \times \frac{0.450mol}{L} = 0.0198 mol$

The molar ratio of H₂SO₄ to NaOH is 1:2. The moles of H₂SO₄ that react with 0.0198 moles of NaOH are:

$0.0198 mol NaOH \times \frac{1molH_2SO_4}{2molNaOH} = 0.00990 molH_2SO_4$

0.00990 moles of H₂SO₄ are in 20.00 mL of solution. The molarity of H₂SO₄ is:

$[H_2SO_4] = \frac{0.00990mol}{0.02000} = 0.495 M$

To standardize 20.00 mL of 0.495 M H₂SO₄ are used 44.10 mL of 0.450 M NaOH in a neutralization reaction.

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