Page 11 - 1202 Question Bank Chemistry Form 4 KSSM

Molecular formula = (Empirical formula)
× molar volume n
Number of moles, n
Number of Volume Volume n × empirical formula = molar mass
moles, n = Molar volume 4.
÷ molar volume Formula that shows the
Empirical simplest whole number
3.3 Chemical Formula formula ratio of atoms of each
element in a compound
1. Chemical formula is a representation of a chemical Chemical
substance using letters to represent the atoms and formulae Formula that shows
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subscript numbers to show the numbers of each the actual number of
type of atoms found in the elementary entities of Molecular atoms of each element
the substance. formula in the molecule of a
2. From the chemical formula, we know: compound

Water is made up of hydrogen and oxygen 3.4 Chemical Equation
H O Relative molecular mass
2 = 2(1) + 16 1. A chemical equation is a precise description of a
chemical reaction.
2 hydrogen 1 oxygen = 18 2. Chemical equation gives us:
Ratio of hydrogen to oxygen
atoms atom
= 2 : 1 (a) Qualitative information – Tell us the reactants
and products involved in the reaction and the
3. Molecular formula can only be determined if we physical states of the reactants and products.
know the empirical formula and molar mass OR (b) Quantitative information – Tells us the exact
relative molecular mass of that substance. proportions (number of moles) of reactants and
products in the reaction.

PAPER 1

Each question has four different answers, A, B, C and D. For each question, choose one answer only.

3.1 Relative Atomic Mass and Relative
Molecular Mass CO 2 C H 10 O 2 N 2
4
1. Why was carbon-12 chosen as the standard atom to
SPM
SPM determine the relative atomic mass of other elements?
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A Carbon has three isotopes. W X Y Z
B Carbon is a solid and easier to be handled. Diagram 1
C Carbon is heavier than oxygen and hydrogen.
D Carbon is located in Group 14 in the Periodic Table Which balloon becomes the smallest after one day?
of Elements. HOTS Applying
[Relative atomic mass: H = 1, C = 12, N = 14,
2. A compound with formula X CO has a relative O = 16]
2
3
SPM
SPM formula mass of 138. What is the relative atomic A W C Y
CLONE B X D Z
mass of X? HOTS Applying
[Relative atomic mass: C=12, O=16]
A 39 C 78 4. The chemical formula for potassium
SPM
B 69 D 110 SPM hexacyanoferrate(II) is K Fe(CN) . What is its relative
4
6
CLONE
formula mass? HOTS Applying
3. Ahmad filled four different types of gases into four [Relative atomic mass: C = 12, N = 14, K = 39, Fe = 56]
SPM balloons as shown in Diagram 1. A 121 C 238
SPM
CLONE B 199 D 368
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Question 3:
The smaller the size of particles, the easier the particles to penetrate through the semipermeable membrane. Therefore, the size of balloon will be reduced. SOS TIP
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