Question detail

Calculate the number of moles in 50 grams of sodium chloride (NaCl). The relative formula mass (Mr) of NaCl is 58.5 g/mol.

Try the question, check the answer, then read the explanation to understand the curriculum point.

Show answer Topic hub Objective page

At a glance

MCQ

Type

practice

Style

Topic

Amount of substance

Question

A. 0.86 mol
B. 1.00 mol
C. 1.71 mol
D. 2.00 mol

Answer

0.86 mol

Explanation

To find the number of moles, use the formula: moles = mass / Mr. Substituting the values gives: moles = 50 g / 58.5 g/mol = 0.8547 mol, which rounds to 0.86 mol.

Common mistake

Misunderstanding the Mole Concept

Students often confuse the mole with the mass of a substance, thinking that the mole is a measure of weight rather than a measure of quantity.

To clarify, remember that the mole is a unit that measures the amount of substance. Use the formula: n = m / Mr, where n is the number of moles, m is the mass in grams, and Mr is the relative formula mass. For example, if you have 18 grams of water (H₂O), calculate the moles as follows: n = 18 g / 18 g/mol = 1 mol. Thus, the answer is 1 mol.

Related flashcards

Flashcard 1 of 5

Press Space to flip, arrows to move