What volume (mL) of .25 M K2Cr2O7 would be required to oxidize 75 mL of 0.25 M Na2SO3 in acidic solution according to the following reaction?

8H⁺ + Cr₂O₇⁻² + 3SO₃⁻² → 2Cr⁺³ + 3SO₄⁻² + 4H₂O
Mole ratio K₂Cr₂O₇ : Na₂SO₃ = Cr₂O₇⁻² : SO₃⁻² = 1 : 3

Moles of Na₂SO₃ reacted = (0.25 mol/L) × (75/1000 L) = 0.01875 mol
Moles of K₂Cr₂O₇ required = (0.01875 mol) × (1/3) = 0.00625 mol
Volume of K₂Cr₂O₇ required = (0.00625 mol) / (0.25 mol/L) = 0.025 L = 25 mL

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OR:

(0.25 mol Na₂SO₃ / 1000 mL Na₂SO₃ solution) × (75 mL Na₂SO₃ solution) × (1 mol K₂Cr₂O₇ / 3 mol Na₂SO₃) × (1000 mL K₂Cr₂O₇ solution / 0.25 mol K₂Cr₂O₇)
= 25 mL K₂Cr₂O₇ solution