Question

Calculate the mass fraction of sodium chloride if it known that 20 gm of sodium chloride is dissolved in 80 gm of water

Answer 1

Answer:

You have 20g of NaCl which is dissolved in 80g pf H2O. So, the total weight is 100g, and 20/100 = 20% is the solute NaCl and 80/100 = 80% is the solvent, water.

Explanation:

Answer 2

Answer:

The mass fraction of sodium chloride, if it is known that 20 gm of sodium chloride is dissolved in 80 gm of water, is 0.07.

Explanation:

The mass fraction is calculated as,

$\mathrm{x=\frac{n_b}{n_a} }$      (1)

Where,

x=mass fraction of solute

$\mathrm{n_a}$=number of moles of the solvent

$\mathrm{n_b}$=number of moles of the solute

From the question we have,

The mass of sodium chloride=20 gm

The mass of water=80 gm

The molar mass of sodium chloride=58.4 gm

The molar mass of water=18 gm

The number of moles of the solute is calculated as,

$\mathrm{n_b=\frac{m}{M} }$         (2)

m=mass of solute

M=molar mass of solute

After plugging the values into equation (2), we get;

$\mathrm{n_b=\frac{20}{58.4} }$          (3)

The number of moles of the solvent is calculated as,

$\mathrm{n_a=\frac{m}{M} }$   (4)

m=mass of solvent

M=mass of solvent

When we enter the values into equation (4), we obtain;

$\mathrm{n_a=\frac{80}{18} }$           (5)

Equation (1) is obtained by integrating equations (3) and (5);

$\mathrm{x=\frac{\frac{20}{58.4} }{\frac{80}{18} } }$

$\mathrm{x=0.07}$

Hence, the mass fraction of sodium chloride, if it is known that 20 gm of sodium chloride is dissolved in 80 gm of water, is 0.07.

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