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Chemistry Form 4 • MODULE

• Empirical formula shows the simplest ratio of number carbon atoms to hydrogen atoms, the simplest
ratio of number of carbon atoms to hydrogen atoms in benzene is 1 : 1 .
Formula empirik benzena menunjukkan nisbah paling ringkas bilangan atoms karbon kepada atom hidrogen .
Nisbah paling ringkas bilangan atom karbon kepada hidrogen adalah 1 : 1 .

PERCENTAGE COMPOSITION BY MASS OF AN ELEMENT IN A COMPOUND
PERATUS KOMPOSISI UNSUR MENGIKUT JISIM DALAM SEBATIAN

Total RAM of the element in the compound × 100%
Jumlah JAR unsur dalam suatu sebatian × 100%
1 % composition by mass of an element =
% komposisi unsur mengikut jisim RMM/RFM of compound/JMR/JFR sebatian
2 Example / Contoh:
Calculate the percentage composition by mass of nitrogen in the following compounds:
Hitungkan peratusan nitrogen mengikut jisim dalam sebatian berikut:
[Relative atomic mass / Jisim atom relatif : N = 14, H = 1, O = 16, S = 32, K = 39]
(i) (NH ) SO 4
4 2
2 × 14
%N = × 100%
132
= 21.2%
(ii) KNO
3
14
%N = × 100%
101
= 13.9%

CHEMICAL FORMULA FOR IONIC COMPOUNDS / FORMULA KIMIA BAGI SEBATIAN ION

m+
1 Chemical formula of an ionic compound comprising of the ions X and Y is by exchanging the charges on each ion.
n–
The formula obtained will be X Y .
m n
Formula kimia sebatian ion yang mengandungi ion X m+ dan Y boleh diperoleh melalui pertukaran bilangan cas setiap ion. Formula yang
n–
diperoleh ialah X Y .
n m
2 Example / Contoh:
(i) Sodium oxide / Natrium oksida
Ion / Ion Na + O 2–
Charges / Bilangan cas +1 –2
Exchange of charges / Pertukaran bilangan cas 2 1

Smallest ratio / Nisbah teringkas 2 1
Number of combining ions / Bilangan ion yang bergabung 2 Na + O 2–
Formula / Formula Na O
2
(ii) Copper(II) nitrate / Kuprum(II) nitrat (iii) Zinc oxide / Zink oksida
Cu 2+ NO 3 – Zn 2+ O 2–
+2 –1 +2 –2

1 2 (Ratio / Nisbah) 2 2
⇒ Cu(NO )
3 2
1 1 (Ratio / Nisbah)
⇒ ZnO

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