Question

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Answer 1

Q. No. 5:

               What is the molarity of 3.20 g of Potassium dissolved into 0.50 L solution.

Answer:

                     Molarity is the the unit of concentration and it is expressed as the amount of solute dissolved per unit volume of solution. It is expressed as,

                         Molarity  =  Moles / Volume of Solution  (1)

Data Given;

                  Mass  =  3.20 g

                  Volume  =  0.50 L

                   A.Mass of K  =  39.10 g/mol

First calculate Moles for given mass as,

                   Moles  =  Mass / M.mass

                   Moles  =  3.20 g / 39.10 g.mol⁻¹

                   Moles  =  0.08184 mol

Now, putting value of Moles and Volume in eq. 1,

                        Molarity  =  0.08184 mol ÷ 0.50 L

                        Molarity  =  0.163 mol.L⁻¹ (or) 0.163 M

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Q. No. 6:

               What is the molarity of 2.31 g of Potassium dissolved into 400 mL solution.

Answer:

Data Given;

                  Mass  =  2.31 g

                  Volume  =  400 mL  =  0.40 L

                   A.Mass of K  =  39.10 g/mol

First calculate Moles for given mass as,

                   Moles  =  Mass / M.mass

                   Moles  =  2.31 g / 39.10 g.mol⁻¹

                   Moles  =  0.0590 mol

As,

                   Molarity  =  Moles / Volume of Solution

Now, putting value of Moles and Volume,

                   Molarity  =  0.0590 mol ÷ 0.40 L

                   Molarity  =  0.147 mol.L⁻¹ (or) 0.147 M

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Q. No. 7:

               How many moles of sodium nitrate are there in 75 mL of 0.25 M solution?

Answer:

Data Given;

                  Moles  =  ??

                  Volume  =  75 mL  =  0.075 L

                  Molarity  =  0.25 mol.L⁻¹

Molarity is given as,

                        Molarity  =  Moles / Volume of Solution

Solving for Moles,

                        Moles  =  Molarity × Volume of Solution

Putting value of Molarity and Volume,

                        Moles  =  0.25 mol.L⁻¹ × 0.075 L

                        Moles =  0.0187 mol