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WAEC Chemistry 2017 Paper

Question : 25

Total: 50

6.02\times 10^{23}

]

Solution:

Concept:

A mole contains Avogadro’s number of particles. Since the gas is triatomic, each molecule has 3 atoms.

Explanation:

Number of molecules in 2.5 moles

= 2.5 \times 6.02 \times 10^{23} = 1.505 \times 10^{24}

molecules.

Because the gas is triatomic, total atoms

= 3 \times 1.505 \times 10^{24} = 4.515 \times 10^{24}

atoms.

So 2.5 moles of a triatomic gas contain about

4.5 \times 10^{24}

atoms.

Answer:

4.515 \times 10^{24}

atoms

\approx 4.5 \times 10^{24}

atoms.

This value is not listed among the provided options.

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