Multiple Choice
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?
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
0.580 moles
B
0.725 moles
C
0.362 moles
D
1.450 moles
Verified step by step guidance1
Start 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 tells us the stoichiometric relationship between KNO3 and O2.
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: mass = 58.6 g and molar mass = 101.11 g/mol.
Determine the stoichiometric ratio between KNO3 and O2 from the balanced equation. According to the equation, 4 moles of KNO3 produce 5 moles of O2.
Use the stoichiometric ratio to calculate the moles of O2 produced. Multiply the moles of KNO3 by the ratio \( \frac{5 \text{ moles of O2}}{4 \text{ moles of KNO3}} \).
Verify your calculations and ensure that the units are consistent throughout the process. This will help confirm the accuracy of the moles of O2 produced.
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