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Question: When 100 ml of $\frac{M}{10}$ H$_2$SO$_4$ is mixed with 500 ml of $\frac{M}{10}$ NaOH then nature of...

When 100 ml of M10\frac{M}{10} H2_2SO4_4 is mixed with 500 ml of M10\frac{M}{10} NaOH then nature of resulting solution and Molarity of excess of reactant left is

A

Acidic, M5\frac{M}{5}

B

Basic, M5\frac{M}{5}

C

Basic, M20\frac{M}{20}

D

Acidic, M10\frac{M}{10}

Answer

(3)

Explanation

Solution

To determine the nature of the resulting solution and the molarity of the excess reactant, we follow these steps:

  1. Calculate the millimoles of H₂SO₄:
    Given, Molarity of H₂SO₄ = M10\frac{M}{10} = 0.1 M
    Volume of H₂SO₄ = 100 ml
    Millimoles of H₂SO₄ = Molarity × Volume (in ml) = 0.1 M × 100 ml = 10 millimoles

  2. Calculate the millimoles of NaOH:
    Given, Molarity of NaOH = M10\frac{M}{10} = 0.1 M
    Volume of NaOH = 500 ml
    Millimoles of NaOH = Molarity × Volume (in ml) = 0.1 M × 500 ml = 50 millimoles

  3. Write the balanced chemical equation for the reaction:
    H₂SO₄ (aq) + 2NaOH (aq) → Na₂SO₄ (aq) + 2H₂O (l)

  4. Determine the limiting and excess reactants:
    From the balanced equation, 1 mole of H₂SO₄ reacts with 2 moles of NaOH.
    This means 1 millimole of H₂SO₄ reacts with 2 millimoles of NaOH.

    We have 10 millimoles of H₂SO₄.
    The amount of NaOH required to react completely with 10 millimoles of H₂SO₄ is:
    10 millimoles H₂SO₄ × (2 millimoles NaOH1 millimole H₂SO₄\frac{2 \text{ millimoles NaOH}}{1 \text{ millimole H₂SO₄}}) = 20 millimoles of NaOH.

    We have 50 millimoles of NaOH initially, which is more than the 20 millimoles required.
    Therefore, NaOH is the excess reactant, and H₂SO₄ is the limiting reactant.

  5. Calculate the millimoles of the excess reactant (NaOH) left:
    Millimoles of NaOH left = Initial millimoles of NaOH - Millimoles of NaOH reacted
    Millimoles of NaOH left = 50 millimoles - 20 millimoles = 30 millimoles

  6. Determine the nature of the resulting solution:
    Since NaOH (a strong base) is in excess, the resulting solution will be Basic.

  7. Calculate the total volume of the solution:
    Total volume = Volume of H₂SO₄ + Volume of NaOH
    Total volume = 100 ml + 500 ml = 600 ml

  8. Calculate the molarity of the excess reactant (NaOH) left:
    Molarity of NaOH left = Millimoles of NaOH leftTotal volume (in ml)\frac{\text{Millimoles of NaOH left}}{\text{Total volume (in ml)}}
    Molarity of NaOH left = 30 millimoles600 ml\frac{30 \text{ millimoles}}{600 \text{ ml}} = 120\frac{1}{20} M

    So, the molarity of excess NaOH left is M20\frac{M}{20}.

Combining the results, the nature of the resulting solution is Basic, and the Molarity of excess reactant left is M20\frac{M}{20}.