Lesson: Chapter 7 — Quantification of Elements and Compounds

Working with moles 5 of 10 Reset answers

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Question 5

What is the mass of 2 moles of urea (CO(NH₂)₂)? (Molar mass = 60 g mol^-1)

A 120 g B 2 g C 30 g D 60 g

The right answer is the one marked above.

120 g. The formula is reversed here: m = n × M = 2 mol × 60 g mol^-1 = 120 g.

30 g comes from dividing instead of multiplying. Moles were given and a mass asked for, so this is a multiplication.

Answer the question to continue.