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MODULE • Chemistry Form 4

CONCENTRATION OF ACID AND ALKALI / KEPEKATAN ASID DAN ALKALI

1 A solution is a homogeneous mixture formed when a solute is dissolved in a solvent. For example copper(II) sulphate
solution is prepared by dissolving copper(II) sulphate powder (solute) in water (solvent).
Larutan adalah campuran homogen yang terbentuk apabila bahan larut dilarutkan dalam pelarut. Contohnya larutan kuprum(II) sulfat
disediakan dengan melarutkan serbuk kuprum(II) sulfat (bahan larut) di dalam air (pelarut).
2 Concentration of a solution the quantity of solute in a given volume of solution which is usually 1 dm of solution.
3
Kepekatan sesuatu larutan ialah kuantiti bahan terlarut dalam isi padu larutan yang tertentu, biasanya isi padu 1 dm larutan.
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3 Concentration can be expressed in two ways / Kepekatan boleh diwakili dengan dua cara :
(a) Mass of solute in gram per 1 dm solution, g dm / Jisim bahan larut dalam gram bagi setiap 1 dm larutan, g dm .
3
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3
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Mass of solute in gram (g) / Jisim bahan larut dalam gram (g)
–3
Concentration of solution (g dm ) =
3
3
Kepekatan larutan (g dm ) Volume of solution (dm ) / Isi padu larutan (dm )
–3

(b) Number of moles of solute in 1 dm solution, mol dm / Bilangan mol bahan larut dalam 1 dm larutan, mol dm .
3
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–3
3
Number of mole of solute (mol) / Bilangan mol bahan larut (mol)
–3
Concentration of solution (mol dm ) =
3
Kepekatan larutan (mol dm ) Volume of solution (dm ) / Isi padu larutan (dm )
3
–3

–3
4 The concentration in mol dm is called molarity or molar concentration. The unit mol dm can be represented by ‘M’.
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Kepekatan dalam mol dm dipanggil sebagai kemolaran atau kepekatan molar. Unit mol dm boleh diwakili dengan‘M’.
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n = Number of moles of solute
Number of mole of solute (mol) / Bilangan mol bahan larut (mol)
Molarity = Bilangan mol bahan terlarut
–3
3
3
Kemolaran Volume of solution (dm ) / Isi padu larutan (dm ) M = Concentration in mol dm
(molarity)
Number of mole of solute (mol) = Molarity × Volume (dm ) Kepekatan dalam mol dm
3
–3
3
Bilangan mol bahan larut (mol) Kemolaran × Isi padu (dm ) (kemolaran)
n = MV V = Volume of solution in dm 3
Mv Isi padu larutan dalam dm 3
n = v = Volume of solution in cm 3
1 000
Isi padu larutan dalam cm
3
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5 The concentration of a solution can be converted from mol dm to g dm and vice versa.
Kepekatan larutan boleh ditukar daripada mol dm kepada g dm dan sebaliknya.
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× molar mass of the solute / jisim molar bahan terlarut
mol dm –3 g dm –3
÷ molar mass of the solute / jisim molar bahan terlarut
6 The pH value of an acid or an alkali depends on the concentration of hydrogen ions or hydroxide ions:
Nilai pH bagi asid atau alkali bergantung pada kepekatan ion hidrogen atau ion hidroksida:
The higher the concentration of hydrogen ions in acidic solution, the lower the pH value.
Semakin tinggi kepekatan ion hidrogen dalam larutan berasid, semakin rendah nilai pH.
The higher the concentration of hydroxide ions in alkaline solution, the higher the pH value.
Semakin tinggi kepekatan ion hidroksida dalam larutan beralkali, semakin tinggi nilai pH.
7 The pH value of an acid or an alkali is depends on / Nilai pH bagi asid atau alkali bergantung pada:
(a) The strength of acid or alkali / Kekuatan asid atau alkali
– the degree of ionisation or dissociation of the acid and alkali in water / darjah pengionan asid atau alkali dalam air.
(b) Molarity of acid or alkali / Kemolaran asid atau alkali
– the concentration of acid or alkali in mol dm / kepekatan bahan terlarut dalam mol dm .
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(c) Basicity of an acid / Kebesan asid
– the number ionisable of hydrogen atom per molecule of an acid molecule in an aqueous solution.
bilangan atom hidrogen per molekul asid yang terion dalam larutan akueus.
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