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Chemistry Form 4 • MODULE

6 Explain why the set-up of apparatus to determine the empirical formula in both the experiments is different.
Terangkan mengapa susunan radas untuk menentukan formula empirik dalam kedua-dua eksperimen itu berbeza.
(a) Magnesium is reactive metal (above hidrogen in reactivity series). Magnesium reacts easily to form
magnesium oxide .
Magnesium adalah logam reaktif (terletak di atas hidrogen dalam siri kereaktifan. Magnesium mudah teroksida
membentuk magnesium oksida .
(b) Copper is below hydrogen in the metal reactivity series. Oxygen in copper(II) oxide can be reduced/removed
by hydrogen gas to form copper and water.

Kuprum di bawah hidrogen dalam siri kereaktifan. Kuprum(II) okida boleh diturunkan/disingkirkan oleh
gas hidrogen untuk membentuk kuprum dan air.

7 To calculate the empirical formula of a compound, use the following table:
Untuk menghitung formula empirik suatu sebatian, jadual di bawah boleh digunakan sebagai panduan:
Calculation steps / Langkah pengiraan:
Element / Unsur
(a) Calculate the mass of each element in the compound.
Mass of element (g) / Jisim unsur (g) Hitungkan jisim setiap unsur dalam sebatian.
(b) Convert the mass of each element to number of mole of atom.
Number of mole of atom / Bilangan mol atom Tukar jisim setiap unsur kepada bilangan mol atom.
(c) Calculate the simplest ratio of moles of atom of the elements.
Simplest ratio of moles / Nisbah mol teringkas
Hitungkan nisbah bilangan mol atom teringkas unsur-unsur tersebut.

EXERCISE / LATIHAN

1 When 11.95 g of metal X oxide is reduced by hydrogen, 10.35 g of metal X is produced. Calculate the empirical formula
of metal X oxide.
Apabila 11.95 g oksida logam X diturunkan oleh hidrogen, 10.35 g logam terhasil. Hitungkan formula empirik bagi oksida logam X.
[RAM / JAR: X = 207, O = 16]

Element / Unsur X O
Mass of element (g) / Jisim unsur (g) 10.35 1.6
Number of mole of atoms / Bilangan mol atom 0.05 0.1
Ratio of moles / Nisbah mol 1 2

Simplest ratio of moles / Nisbah mol teringkas 1 2
Empirical formula / Formula empirik: XO 2 .

2 A certain compound contains the following composition / Satu sebatian mengandungi komposisi unsur seperti berikut:
Na = 15.23%, Br = 52.98%, O = 31.79 % [Relative atomic mass / Jisim atom relatif: O = 16, Na = 23, Br = 80]
(Assume that 100 g of substance is used / Anggap 100 g bahan digunakan)

Element / Unsur Na Br O
Mass of element (g) / Jisim unsur (g) 15.23 52.98 31.79
Number of mole of atoms / Bilangan mol atom 0.66 0.66 1.99

Ratio of moles / Nisbah mol 1 1 3.01
Simplest ratio of moles / Nisbah mol teringkas 1 1 3

Empirical formula / Formula empirik: NaBrO 3 .

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