Question detail
If 5 g of magnesium oxide (MgO) is produced from the reaction of magnesium with oxygen, how many moles of MgO are formed? (Mr of MgO = 40.3 g/mol)
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Use of amount of substance in relation to masses of pure substances
Question
- A. 0.12 mol
- B. 0.10 mol
- C. 0.15 mol
- D. 0.20 mol
Answer
0.12 mol
Explanation
The number of moles is calculated using the formula moles = mass / Mr. Here, moles = 5 g / 40.3 g/mol = 0.124 mol, which rounds to 0.12 mol.
Common mistake
Common Mistake in Balancing Equations
Students often confuse the masses of reactants and products with their mole ratios when balancing equations.
To fix this, students should first convert the given masses into moles using the relative formula mass before applying the mole ratios from the balanced equation.
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