Question

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3
Eight (8) grams of Na2S2O3 is dissolved in water to prepare 500 cm
of solution. Calculate the concentration of the Na2S 20-3 solution.
(4)​

Answer 1

Answer:

The concentration of the Na2S 203 solution is 0.101 mol/L

Explanation:

Concentration is the molarity of the solution which is defined as the number of moles of solute per unit volume of the solution in Litres.

Molarity(Concentration) = Moles/Volume in L

It is given that:

The mass of Na2S2O3 = 8 g

The molar mass of Na2S2O3 = 158.11 g/mol

The volume of solution = 500 cm³

[ 1 cm³ = 0.001 L]

There moles can be calculated as:

moles = mass/ molar mass

moles = 8 g/158.11 gmol-1

moles = 0.0505 mol

Thus, concentration can be given as:

Molarity(Concentration) = Moles/Volume

Molarity(Concentration) = 0.0505mol/500x0.001 L

Molarity(Concentration) = 0.101 mol/L