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Multiple Choice
How many milliliters of 0.200 M FeCl3 are needed to react with an excess of Na2S to produce 0.172 g of Fe2S3 if the percent yield for the reaction is 65.0%?
A
25.0 mL
B
30.0 mL
C
12.5 mL
D
18.2 mL
Verified step by step guidance
1
First, write the balanced chemical equation for the reaction between FeCl3 and Na2S to form Fe2S3: .
Calculate the moles of Fe2S3 produced using its molar mass. The molar mass of Fe2S3 is approximately 207.9 g/mol. Use the formula: . Substitute the given mass of Fe2S3 (0.172 g) and its molar mass to find the moles.
Determine the theoretical moles of Fe2S3 that would be produced if the reaction had a 100% yield. Use the percent yield formula: . Rearrange to solve for the theoretical yield.
Use the stoichiometry of the balanced equation to find the moles of FeCl3 needed. From the balanced equation, 2 moles of FeCl3 produce 1 mole of Fe2S3. Use this ratio to calculate the moles of FeCl3 required.
Finally, calculate the volume of 0.200 M FeCl3 solution needed using the formula: . Substitute the moles of FeCl3 and the molarity to find the volume in milliliters.