Multiple Choice
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?
3. Chemical Reactions
Stoichiometry
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How many moles of oxygen gas (O2) are produced when 58.6 g of KNO3 decomposes according to the reaction: 4 KNO3(s) → 2 K2O(s) + 2 N2(g) + 5 O2(g)? The molar mass of KNO3 is 101.11 g/mol.
A
0.725 moles
B
1.81 moles
C
0.362 moles
D
1.45 moles
Verified step by step guidance1
Step 1: Begin by identifying the balanced chemical equation for the decomposition of KNO3: 4 KNO3(s) → 2 K2O(s) + 2 N2(g) + 5 O2(g). This equation shows the stoichiometric relationship between KNO3 and O2.
Step 2: Calculate the number of moles of KNO3 using its molar mass. Use the formula: \( \text{moles of KNO3} = \frac{\text{mass of KNO3}}{\text{molar mass of KNO3}} \). Substitute the given values: \( \text{mass of KNO3} = 58.6 \text{ g} \) and \( \text{molar mass of KNO3} = 101.11 \text{ g/mol} \).
Step 3: Use the stoichiometry of the balanced equation to find the moles of O2 produced. According to the equation, 4 moles of KNO3 produce 5 moles of O2. Set up the ratio: \( \frac{5 \text{ moles O2}}{4 \text{ moles KNO3}} \).
Step 4: Multiply the moles of KNO3 calculated in Step 2 by the stoichiometric ratio from Step 3 to find the moles of O2 produced: \( \text{moles of O2} = \text{moles of KNO3} \times \frac{5}{4} \).
Step 5: Review the calculation steps to ensure accuracy and consistency with the stoichiometric relationships in the balanced equation.
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