Question

calculate the molarity of solution containing 20.7g of pottasium carbonate dissolved in 500ml of solution. assume density is 1gm/ml

Answer 1

Formula used , Molality = Moles of solute/ Kg of solvent

Moles of solute = given wt. of K2CO3/ Mol. wt. of K2CO3 = 20.7g/ 138g = 0.15 moles.

Solvent used is 500mL = 500g (Given density = 1gram/mL) = )0.5Kg

Molality = Moles of solute/ Kg of solvent =0.15/0.5= 0.3

Concentration of solution is 0.3Molal.

Answer 2

Answer:

The molality and molarity of a solution containing 20.7g of potassium Carbonate in 500 ml of the solution is 0.3 Molal and 0.3 M respectively.

Explanation:

Step 1 : Differentiating molality and molarity.

Molality = Moles per kilogram of a solvent.

Molarity = Moles per 1 liter of a solution.

Step 2 : Calculate the moles of Potassium Carbonate.

Molar mass of Potassium Carbonate:

K2CO3 = 39 × 2 + 12 + 16 × 3 = 138 g/mol

Moles of Potassium Carbonate = 20.7/138 = 0.15 moles.

Step 2: Calculate molarity.

0.15 moles —> 500ml

? —> 1000 ml

By cross multiplication :

1000/500 × 0.15 = 0.3 M

Molarity = 0.3 M

Step 3 : Calculate molality :

Calculate the mass of the solvent.

Density = 1 g/ml

Volume = 500 ml

Mass = Density × volume

= 1 g/ml × 500 ml = 500g

Convert this to kgs.

500/1000 = 0.5 kg

0.15 moles —> 0.5kg

? —> 1 kg

By cross multiplication :

1/0.5 × 0.15 = 0.3 moles per kilogram of solvent.