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%?
3. Chemical Reactions
Stoichiometry
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How many moles of H₂ can be formed if a 2.83 g sample of Mg reacts with excess HCl according to the reaction: Mg + 2HCl → MgCl₂ + H₂?
A
0.116 moles
B
0.232 moles
C
0.058 moles
D
0.174 moles
Verified step by step guidance1
First, identify the balanced chemical equation for the reaction: \( \text{Mg} + 2\text{HCl} \rightarrow \text{MgCl}_2 + \text{H}_2 \). This equation shows that one mole of Mg reacts with two moles of HCl to produce one mole of H₂.
Calculate the molar mass of Mg. The atomic mass of Mg is approximately 24.31 g/mol. This will be used to convert the mass of Mg to moles.
Convert the mass of Mg to moles using the formula: \( \text{moles of Mg} = \frac{\text{mass of Mg}}{\text{molar mass of Mg}} \). Substitute the given mass of Mg (2.83 g) and the molar mass (24.31 g/mol) into the formula.
Use the stoichiometry of the balanced equation to determine the moles of H₂ produced. According to the equation, 1 mole of Mg produces 1 mole of H₂. Therefore, the moles of H₂ formed will be equal to the moles of Mg calculated in the previous step.
Review the possible answers and compare them to the calculated moles of H₂ to determine which option matches the calculated value.
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