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WAEC Chemistry 2016 Paper

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Question : 17

Total: 50

How many moles of oxygen would contain 1.204 x 10²⁴ molecules?

[Avogadro's constant (NA) = 6.02 x 10²³]

1
2
3
4

Solution:

Concept:

One mole of any substance contains Avogadro’s constant,

6.02 \times 10^{23}

molecules.

Explanation:

Given number of molecules =

1.204 \times 10^{24}

.

Number of moles =

\frac{\text{number of molecules}}{N_A}

.

N_A = 6.02 \times 10^{23}

molecules per mole.

So, moles =

\frac{1.204 \times 10^{24}}{6.02 \times 10^{23}}

.

This simplifies to

\frac{1.204 \times 10}{6.02} = \frac{12.04}{6.02} = 2

moles.

Answer:

The number of moles is

2

moles. Correct option: B.

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