Page 12 - 1202 Question Bank Chemistry Form 4 KSSM

PAPER 2

Section A
Answer all questions.

1. (a) (i) What is the chemical formula of ammonia molecule? [1 mark]
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SPM

CLONE
(ii) What is the name of the isotope of the element that is used as the standard to determine the relative atomic
mass of other elements? [1 mark]

(b) (i) What is the mass of 6.0 dm of ammonia gas, NH at room conditions? [2 marks]
3
3
HOTS Applying
[1 mol of gas occupies 24 dm at room conditions; molar mass of NH = 17 g mol ]
–1
3
3

(ii) How many molecules are there in 6.0 dm of ammonia gas? HOTS Applying [1 mark]
3
[Avogadro’s constant = 6.02 × 10 ]
23

(iii) Explain briefly the relationship between the volume, mass and the number of molecules of ammonia in 1(b)
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(i) and 1(b)(ii) at room conditions. [3 marks]

2. Atom is very small and it is impossible to weigh the mass of an atom using any electronic balance. Thus, chemist
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SPM compares the mass of an atom with a standard atom. The mass obtained through comparison is called relative atomic
CLONE 1
mass. Diagram 1 shows the comparison of mass of lithium atom with 12 of carbon-12 atom.
1
12 of a carbon-12 atom
Li C-12

1
12 of a carbon-12 atom

Diagram 1
(a) What is the meaning of relative atomic mass? [1 mark]

33
Question 1:
(b) (i) (b) (iii) When explaining the relationship,
Mass(g) relate the volume, mass and number
× Molar mass ÷ Molar mass of molecules to the number of moles. SOS TIP
× N A × Molar volume
33
Number of particles Number of moles Volume of gas 33
÷ N A ÷ Molar volume