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
