[Chemistry Form 4] Concentration Of Solution

The concentration of a solution refers to the quantity of solute in a given volume of solution. The units can be expressed in two forms:

Concentration of solution in g dm^-3
= Mass of solute (g) / Volume of solution (dm³)

Concentration of solution in mole dm^-3 (molarity)
= Number of moles of solute (mole) / Volume of solution (dm³)

*******

1. 20g of sodium hydroxide is dissolved in 500cm³ of solution. Calculate the
a) concentration of the solution in g dm^-3
40g dm^-3

b) molarity of the solution in mole dm^-3
( Relative atomic mass of Na = 23; O = 16; H = 1)
1 mole dm^-3

2. Calculate the number of moles of calcium hydroxide in 250cm³ of 0.5 mole dm^-3 calcium hydroxide solution.
Hint: The number of moles = Molarity X Volume in dm³
0.5 X (250/1,000)

3. Calculate the mass of calcium hydroxide in 200cm³ of 0.4 mole dm^-3 calcium hydroxide solution.
(Relative atomic mass of Ca = 40; O = 16; H = 1)
Hint: Find the number of moles of calcium hydroxide first.
0.4 X (200/1,000) X RMM of Ca(OH)₂

4. You are required to prepare 250cm³ of 5 mole dm^-3 sodium hydroxide solution. Calculate the mass of sodium hydroxide required.
(Relative atomic mass of Na = 23; O = 16; H = 1)
Hint: Find the number of moles of sodium hydroxide first.
5 X (250/1,000) X RMM NaOH