Final answer:
To react with one mole of ferric sulphite, 0.1666 moles (approximately 0.6 moles) of K₂Cr₂O₇ will be needed in an acidic medium, therefore the answer is B. 0.6.
Step-by-step explanation:
The question asks for the number of moles of K₂Cr₂O₇ required to react with one mole of ferric sulphite in an acidic medium. The stoichiometry of the reaction should be considered to find the answer. According to the balanced chemical equation provided, 1 mole of K₂Cr₂O₇ reacts with 6 moles of Fe²⁺. Therefore, for each mole of Fe³⁺ produced from ferric sulphite, 1/6 mole of K₂Cr₂O₇ is required. Thus, the correct answer is that it would require 0.1666 moles (approximately 0.6 moles) of K₂Cr₂O₇ to react with one mole of ferric sulphite. Hence, the answer is B. 0.6.