Multiple Choice
How many milliliters of 0.200 M FeCl3 are needed to react with an excess of Na2S to produce 1.38 g of Fe2S3 if the percent yield for the reaction is 65.0%? 3 Na2S(aq) + 2 FeCl3(aq) → Fe2S3(s) + 6 NaCl(aq)
3. Chemical Reactions
Stoichiometry
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How many moles of H₂ can be formed if a 2.97 g sample of Mg reacts with excess HCl according to the reaction: Mg + 2HCl → MgCl₂ + H₂?
A
0.244 moles
B
0.122 moles
C
0.183 moles
D
0.061 moles
Verified step by step guidance1
Determine the molar mass of magnesium (Mg) by using the periodic table. The atomic mass of Mg is approximately 24.31 g/mol.
Calculate the number of moles of Mg in the 2.97 g sample using the formula: \( \text{moles of Mg} = \frac{\text{mass of Mg}}{\text{molar mass of Mg}} \).
Write the balanced chemical equation for the reaction: \( \text{Mg} + 2\text{HCl} \rightarrow \text{MgCl}_2 + \text{H}_2 \).
Use the stoichiometry of the balanced equation to find the moles of \( \text{H}_2 \) produced. According to the equation, 1 mole of Mg produces 1 mole of \( \text{H}_2 \).
Calculate the moles of \( \text{H}_2 \) formed using the moles of Mg calculated in step 2, since the ratio is 1:1.
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