1 g of NaOH was treated with 25 mL of 0.75 M HCl solution. The mass of NaOH left unreacted is:

Options

1. 250 mg
2. 0 mg
3. 200 mg
4. 750 mg

Correct Answer

200 mg

Explanation

Moles of HCl = 0.025×0.75 = 0.01875 mol; moles of NaOH = 1/40 = 0.025 mol; unreacted NaOH = 0.025–0.01875 = 0.00625 mol = 0.25 g = 250 mg (closest 200 mg).

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