What is the concentration of a solution containing 2g of NaOH in 100cm 3 of solution? [Na=23, O=16, H=1]

Correct Answer is : 0.50 moldm-3

Correct Answer is : 0.50 moldm-3

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JAMB Chemistry 2016 Paper

Question : 15

Total: 50

[Na=23, O=16, H=1]

Solution:

Concept:

Concentration is the amount of solute in moles per cubic decimetre of solution.

Explanation:

First, convert the volume from

\mathrm{cm}^3

\mathrm{dm}^3

Since

1000\ \mathrm{cm}^3 = 1\ \mathrm{dm}^3

, we have:

100\ \mathrm{cm}^3 = 0.1\ \mathrm{dm}^3

Next, find the molar mass of

\mathrm{NaOH}

23 + 16 + 1 = 40\ \mathrm{g/mol}

Calculate the number of moles in

2\ \mathrm{g}

\mathrm{NaOH}

\text{moles} = \frac{2}{40} = 0.05\ \mathrm{mol}

Now find the concentration:

\text{concentration} = \frac{0.05\ \mathrm{mol}}{0.1\ \mathrm{dm}^3} = 0.50\ \mathrm{mol/dm}^3

Answer:

The concentration is

0.50\ \mathrm{mol/dm}^3

Therefore, the correct option is C.

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