A sample contains 75 g NaCl with a molar mass of 58 g/mol. How many moles are present?

A sample contains 75 g NaCl with a molar mass of 58 g/mol. How many moles are present?

• A. 1.0 moles
• B. 1.3 moles
• C. 0.75 moles
• D. 2.0 moles

Answer: (B)

To find how many moles are present, divide the mass by the molar mass. The molar mass of NaCl is 58 g/mol, so moles = 75 g ÷ 58 g/mol ≈ 1.293 mol. With two significant figures, that becomes about 1.3 moles. So the sample contains roughly 1.3 moles. For perspective, 1.0 mol would correspond to 58 g, 0.75 mol to 43.5 g, and 2.0 mol to 116 g, which don’t match the given mass.

To find how many moles are present, divide the mass by the molar mass. The molar mass of NaCl is 58 g/mol, so moles = 75 g ÷ 58 g/mol ≈ 1.293 mol. With two significant figures, that becomes about 1.3 moles. So the sample contains roughly 1.3 moles. For perspective, 1.0 mol would correspond to 58 g, 0.75 mol to 43.5 g, and 2.0 mol to 116 g, which don’t match the given mass.