Page 6 - Modul A+ Kimia Tg 4_Pan Asia Publications

Contoh/ Example:
1 daripada satu atom karbon-12
12
O 1 of a carbon-12 atom
H H 12

Rajah/Diagram 3.2
1
Berdasarkan Rajah 3.2, jisim 1 molekul air ialah 18 kali besar daripada kali jisim satu atom karbon-12.
12

Based on Diagram 3.2, the mass of 1 water molecule is 18 times greater than 1 times of the mass of a carbon-12
atom. 12
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Maka, jisim molekul relatif bagi air/Therefore, the relative molecular mass of water = 18

2. Istilah jisim molekul relatif, JMR hanya boleh digunakan untuk bahan yang terdiri daripada molekul. Bagi sebatian
ion, istilah jisim formula relatif, JFR digunakan.
The term relative molecular mass, RMM can only be used for substances that are made up of molecules. For ionic compounds,
the term relative formula mass, RFM is used instead.

Contoh/Example 4 TP 3
Hitungkan jisim molekul relatif, JMR bagi setiap sebatian yang berikut.
Calculate the relative molecular mass, RMM for each of the following compounds.
[JAR/ RAM: C =12; Cl = 35.5; O = 16, H = 1, N = 14]
(a) Ammonia/ Ammonia, NH 3
(b) Asid etanoik/ Ethanoic acid, CH COOH
3
(c) Tetraklorometana/ Tetrachloromethane, CCl
4
Penyelesaian/Solution :
(a) Jisim molekul relatif ammonia, NH = 14 + 3 (1) = 14 + 3 (1) = 17
Relative molecular mass of ammonia 3
JAR N/ RAM of N JAR H/ RAM of H
2 C 4 H 2 O
(b) Jisim molekul relatif asid etanoik, CH COOH = 2 (12) + 4 (1) + 2 (16) = 24 + 4 + 32 = 60
3
Relative molecular mass of ethanoic acid
JAR C JAR H JAR O
RAM of C RAM of H RAM of O

(c) Jisim molekul relatif tetraklorometana, CCl = 12 + 4 (35.5) = 12 + 142 = 154
4
Relative molecular mass of tetrachloromethane
JAR C/ RAM of C JAR Cl/ RAM of Cl

Contoh/Example 5 TP 3
Hitungkan jisim formula relatif, JFR bagi setiap sebatian ion yang berikut.
Calculate the relative formula mass, RFM for each of the following ionic compounds.
[JAR/ RAM: O = 16; Mg = 24; N = 14; Cl = 35.5; S = 32; H = 1; Cu = 64]
(a) Magnesium oksida/ Magnesium oxide, MgO
(b) Kuprum(II) klorida/ Copper(II) chloride, CuCl 2
(c) Ammonium sulfat/ Ammonium sulphate, (NH ) SO
4 2 4
Penyelesaian/Solution :
(a) Jisim formula relatif magnesium oksida, MgO = 24 + 16 = 40
Relative formula mass of magnesium oxide
JAR Mg JAR O
RAM of Mg RAM of O
(b) Jisim formula relatif kuprum(II) klorida, CuCl = 64 + 2 (35.5)
2
Relative formula mass of copper(II) chloride = 135
(c) Jisim formula relatif ammonium sulfat, (NH ) SO = 2[14 + 4(1)] + 32 + 4(16)
4 2
4
Relative formula mass of ammonium sulphate = 132
35