Page 40 - Nilam_Publication_module_Chemistry_Form.pdf

MODULE • Chemistry Form 4

EXERCISE / LATIHAN
1 The empirical formula of compound X is CH and relative molecular mass is 56. Determine the molecular formula of
2
compound X. [Relative atomic mass: H = 1; C = 12]
Formula empirik sebatian X adalah CH dan JMR adalah 56. Tentukan formula molekul sebatian X. [Jisim atom relatif: H = 1; C = 12]
2
(12 + 2)n = 56
56
n = = 4
14
Molecular formula = (CH ) = C H
4
2 4
8
2 2.58 g of a hydrocarbon contains 2.16 g of carbon. The relative molecular mass of the hydrocarbon is 86.
2.58 g suatu hidrokarbon mengandungi 2.16 g karbon. Jisim molekul relatif bagi hidrokarbon ini ialah 86.
[Relative atomic mass / Jisim atom relatif : H = 1; C = 12]
(i) Calculate the empirical formula of the hydrocarbon / Hitungkan formula empirik bagi hidrokarbon ini.

Element C H
Mass of element (g) 2.16 0.42

Number of mole of atoms 0.18 0.42
Ratio of moles 1 2 1 = 7
3 3
Simplest ratio of moles 3 7
Empirical formula = C H
3 7
(ii) Determine the molecular formula of the hydrocarbon / Tentukan formula molekul hidrokarbon tersebut.
(12 × 3 + 7 × 1)n = 86
86
n = = 2
43
Molecular formula = (C H ) = C H
3 7 2 6 14

3 The diagram below shows the structural formula for benzene molecule.
Rajah di bawah menujukkan formula struktur bagi benzena.
H
H C C C H

H C C C H

H
(a) Name the element that make up benzene / Namakan unsur yang membentuk benzena.
Carbon and hydrogen

(b) What are the molecular formula and empirical formula for benzene?
Apakah formula molekul dan formula empirik bagi benzena?
Molecular formula / Formula molekul: C H 6
6
Empirical formula / Formula empirik: CH
(c) Compare and contrast the molecular formula and empirical formula for benzene.
Banding dan bezakan formula molekul dan formula empirik bagi benzena.
• Both empirical formula and molecular formula shows benzene is made up of carbon and hydrogen
elements.
Kedua-dua fomula molekul dan formula empirik menunjukkan benzena terdiri dari unsur karbon dan hidrogen .
• Molecular formula shows the actual number of carbon atoms and hydrogen atoms in benzene
molecule . Each benzene molecule consists of 6 carbon atoms and 6 hydrogen atoms.
Formula molekul menunjukkan bilangan sebenar bagi atom karbon dan atom hidrogen dalam molekul
benzena. Setiap molekul benzena terdiri daripada 6 atom karbon dan 6 atom
hidrogen .
38
Nilam Publication Sdn. Bhd.

02-Chem F4 (3P).indd 38 12/9/2011 5:59:08 PM