Question

What is the molarity of 25 g of NaNO3 is dissolved in 400 ml of solution?

Answer 1

What is the molarity of 25 g of NaNO3 is dissolved in 400 ml of solution?

Solution:

First we need to find the moles in 25g of NaNO3.

To find moles we use the overall mass (Mr) and we get it from the periodic table.

$$Mr(\mathrm{Na\ N\ O3}) = 23 + 14 + 16 \times 3 = 85\ \mathrm{g} \text{ so we know that } 85\ \mathrm{g} \text{ are in one mole of NaNO3}.$$

To get the moles we convert $\frac{25g \times 1\ \mathrm{mole}}{85g} = 0,29\ \mathrm{mole}$

Now we convert ml into L. $\frac{400\ \mathrm{ml} \times 1\ \mathrm{L}}{1000\ \mathrm{ml}} = 0,4\ \mathrm{L}$

Molarity = Moles of solute / Liters of solution. $C_M = \frac{v}{V}$

$$C_M = \frac{0,29\ \mathrm{mol}}{0,4\ \mathrm{L}} = 0,73\ \mathrm{mol/L}$$

Note: mole / Liter (mol/L) is the unit for molarity ($C_M$).

Answer:

$$0,73\ \mathrm{mol/L}$$