Question

calculate the concentration in mol/L, of a 20% (m/m) solution of sodium hydroxide that has a density of 1.43 g/ml

Answer 1

Answer on the Question #64161, Chemistry / Inorganic chemistry

calculate the concentration in mol/L, of a 20% (m/m) solution of sodium hydroxide that has a density of 1.43 g/ml

Solution:

Assume, that volume of the solution is 100 ml (V=100 ml). Mass of solution equal to:

$$m(\text{solution}) = V \cdot d = 100 \cdot 1.43 = 143 \text{ g}$$

Now we can find the mass of sodium hydroxide:

$$m(\text{NaOH}) = \frac{m(\text{solution}) \cdot 20\%}{100\%} = \frac{143 \cdot 20\%}{100\%} = 28.6 \text{ g}$$

Concentration of NaOH in solution equal to:

$$c(\text{NaOH}) = \frac{m(\text{NaOH}) \cdot 1000}{M(\text{NaOH}) \cdot V} = \frac{28.6 \cdot 1000}{40 \cdot 100} = 7.15 \frac{\text{mol}}{\text{L}}$$

**Answer**: concentration of sodium hydroxide equal to 7.15 mol/L.

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