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Chemistry Form 4 • MODULE

EXERCISE / LATIHAN

1 The equation shows the reaction between zinc and hydrochloric acid.
Persamaan menunjukkan tindak balas antara zink dengan asid hidroklorik.

Zn + 2HCl ZnCl + H
2 2
3
Calculate the mass of zinc required to react with excess hydrochloric acid to produce 6 dm of hydrogen gas at room
3
conditions. [Relative atomic mass: Zn = 65, Cl = 35.5, 1 mole of gas occupies 24 dm at room conditions]
3
Hitungkan jisim zink yang perlu ditindakbalaskan dengan asid hidroklorik berlebihan untuk menghasilkan 6 dm gas hidrogen pada
keadaan bilik. [Jisim atom relatif: Zn = 65, Cl = 35.5, 1 mol gas menempati 24 dm pada suhu bilik]
3
6 dm 3
Mol of H = = 0.25 mol
3
2 24 dm mol –1
From the equation,
1 mol of H : 1 mol of Zn
2
0.25 mol of H : 0.25 mol of Zn
2
Mass of Zn = 0.25 × 65 = 16.2 g

2 The equation shows the reaction between potassium and oxygen.
Persamaan berikut menunjukkan tindak balas antara kalium dengan oksigen.
4K + O 2K O
2 2

Calculate the mass of potassium required to produce 23.5 g of potassium oxide. [Relative atomic mass: K = 39, O = 16]
Hitungkan jisim kalium yang diperlukan untuk menghasilkan 23.5 g kalium oksida. [Jisim atom relatif: K = 39, O = 16]

23.5 23.5
Mol of K O = = = 0.25 mol
2 (2 × 39 + 16) 94
From the equation,
2 mol of K O : 4 mol of K
2
0.25 mol of K O : 0.5 mol of K
2
Mass of K = 0.5 mol × 39 g mol = 19.5 g
–1

3 The equation shows the decomposition of hydrogen peroxide.
Persamaan menunjukkan penguraian hidrogen peroksida.

H O H O + O
2 2 2 2
Balance the equation above. Calculate the number of moles of H O that decomposes if 11.2 dm oxygen gas is collected
3
2
2
at STP. [Relative Atomic mass: H = 1, O = 16, molar volume of gas = 22.4 dm mol at STP]
3
–1
3
Seimbangkan persamaan di atas. Hitung bilangan mol H O yang telah terurai sekiranya 11.2 dm gas oksigen dikumpulkan pada STP.
2
2
3
–1
[Jisim atom relatif: H = 1, O = 16, isi padu molar gas = 22.4 dm mol pada STP]
11.2 dm 3
Mol of O = 22.4 dm mol –1 = 0.5 mol
2
3
From the equation,
1 mol of O : 2 mol of H O
2
2
2
0.5 mol of O : 1.0 mol of H O
2
2
2
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