Question detail
Calculate the number of moles in 50 g of water (H2O). The relative formula mass (Mr) of water is 18 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. 2.78 mol
- B. 0.56 mol
- C. 1.39 mol
- D. 3.00 mol
Answer
2.78 mol
Explanation
The number of moles is calculated using the formula moles = mass / Mr. Here, moles = 50 g / 18 g/mol = 2.78 mol.
Common mistake
Confusing Ratios
Students often confuse mole ratios with mass ratios when balancing equations, leading to incorrect calculations.
To avoid this mistake, always identify whether you are working with moles or masses and use the correct ratios from the balanced equation.
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