Concentration of a solution (Titration)

Question 1

What is a solution?

Answer 1

A solution is a homogeneous mixture containing a substance (solute) dissolved in another substance (solvent).

Solute + Solvent = Solution

Question 2

What is an excellent medium for chemical reactions and why?

Answer 2

Water. Water is an excellent medium for chemical reactions due to it solvent property.

Question 3

What is an aqueous mixture?

Answer 3

A solution containing a substance dissolved in water as solvent is known as an aqueous mixture.

Question 4

What is a saturated solution?

Answer 4

A solution that contains the maximum amount of solute that can be dissolved in a given volume of solution at a particular temperature is known as a saturated solution.

Question 5

What does the concentration of a solution tell us?

Answer 5

The concentration of a solution tells us how much solute is dissolved in per unit volume of the solution.

Question 6

What are the two ways to measuring the concentration of a solution?

Answer 6

1. Mole concentration (Molarity)

The mole concentration (or molarity) of a solution is the no. Of moles of the solute dissolved in per unit volume (1 dm cube) of the solution.

Unit: mol/dm vibe or mol dm to the power of -3 or M (pronounced as ‘molar’)

A solution with a molarity of 0.1 mol/dm cube (0.1M) contains 0.1 mole of the solute dissolved in every 1 dm cube of the solution.

The molarity of a solution can be calculated using the following equation:
Molarity of a solution (mol/dm cube) = No. of moles of solute (in mol) / volume of solution (in dm cube)

Note: We can use a square bracket to denote mole concentration.

Thus instead of writing
Mole concentration of NaOh = 1.00 mol dm to the power of -3

We can write
[NaOH] = 1.00 mol dm to the power of -3

2. Mass concentration

The mass concentration of a solution is the no. Of grams of the solute dissolved in per unit volume (1 dm cube) of the solution.

Unit: g/ dm cube or g dm to the power of -3

A solution of mass concentration 10g/dm cube contains 10g of solute dissolved in every 1 dm cube of the solution.

Question 7

A solution with a molarity of 0.1 mol/dm cube (0.1M) contains __________________ dissolved in every _________ of the solution.

Answer 7

Contains 0.1 mole of the solute dissolved in every 1 dm cube of the solution.

Question 8

What do we use to denote mole concentration?

Answer 8

We can use a square bracket.

Thus instead of writing
Mole concentration of NaOh = 1.00 mol dm to the power of -3

We can write
[NaOH] = 1.00 mol dm to the power of -3

Question 9

A solution of mass concentration 10g/dm cube contains ________ of solute dissolved in every _____ of the solution.

Answer 9

A solution of mass concentration 10g/dm cube contains 10g of solute dissolved in every 1 dm cube of the solution.

Question 10

The mass of the sodium chloride is 11.7g

The volume of solution formed is 250 cm cube.

What is the concentration of solution?

Answer 10

Mass concentration of solution
= 11.7 g / 0.250 dm cube
= 46.8

Question 11

Sodium chloride —> 0.200 mol
Volume of solution formed —> 250 cm cube

What is the concentration of solution?

Answer 11

Mole concentration of solution
= 0.200 mol/0.250 dm cube
= 0.800 mol/dm cube or 0.800M

Question 12

Suppose we start with a solution with solute concentration of 1.00 mol dm cube, which may be represented in a diagram where 1 dm cube of solution contains 1.00 mole of solute, where 12 black dots represent 1.00 mol of solute.

If we pour out 0.500 dm cube (or 500 cm cube) of the solution into another beaker, what is the amount of solute obtained? What is the concentration of the solution in the beaker?

Answer 12

If represented in a diagram where
500 cm cube of solution contains 0.500 mole of solute [represented by 6 black dots]

Answer: 0.500 mol of solute is obtained. However, the concentration of the solution remains the same, 1.00 mol dm cube.

Question 13

Converting between mole concentration and mass concentration

1. We know that the molar mass (or relative molecular mass) is key in converting between amount (in mol) and mass (in g), e.g. Molarity mass of H2O = 18 g/mol, thus if you have 10.0g of H2O you would have 10.0 divide by 18 = 0.556 mol of H2O.

In similar manner, the conversion between mole concentration and mass concentration uses the molar mass as well.

What is the formula that can be applied?

Answer 13

Mass concentration of a solution (g dm to the power of -3) = Mole concentration of the solution (mol dm to the power of -3) x Molarity mass of solute (g mol to the power of -1)

Note that since measured values are given in 3s.f. Your calculated values should be presented din 3 s.f.