NECO 2001 Chemistry · Question 20

Which element contains the greatest number of moles?

Options

A.8 g of Helium
B.48 g of Carbon
C.78 g of Potassium
D.130g of Zinc
E.216g of Sliver

Answer: B. 48 g of Carbon

Explanation written with AI and checked against the answer key

Concept: Number of moles = mass ÷ molar mass (atomic mass for elements).

Atomic masses used: He = 4, C = 12, K = 39, Zn = 65, Ag = 108

Step-by-step calculation:

A. Helium: 8 ÷ 4 = 2 moles
B. Carbon: 48 ÷ 12 = 4 moles
C. Potassium: 78 ÷ 39 = 2 moles
D. Zinc: 130 ÷ 65 = 2 moles
E. Silver: 216 ÷ 108 = 2 moles

Comparison: Every option gives 2 moles except carbon, which gives 4 moles. So carbon has the greatest number of moles.

Tip: In "greatest number of moles" questions, you don't always need to finish every calculation. Look for numbers that divide neatly (like 48 ÷ 12 = 4) and compare quickly. Light elements with large masses usually give the most moles, but check helium too, since its small atomic mass can surprise you (here it only gives 2 because the mass is just 8 g).

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