Page 12 - Focus SPM KSSM F4 2020 - Chemistry

Chemistry Form 4 Chapter 3 The Mole Concept, Chemical Formula and Equation
• Room conditions refer to the temperature
of 25ºC and the pressure of 1 atm. EXAMPLE 3.11
What is the volume of 1.2 moles of neon gas at
STP?
1 mole of H 2 1 mole of O 2 1 mole of N 2 [Molar volume: 22.4 dm mol at STP]
3
-1
Solution
The volume of neon gas
Figure 3.6 Each balloon has 6.02 x 10 molecules and has = number of moles × molar volume
23
the volume of 22.4 dm at STP = 1.2 × 22.4 dm 3
3
= 26.88 dm 3
4. Number of moles and volume of gas are linked
by molar volume as shown below.
Number × molar volume Volume EXAMPLE 3.12
of moles ÷ molar volume of gas 100 cm of carbon dioxide gas is collected in a
3
reaction at room conditions. How many moles
Chapter
3 SPM Tips of carbon dioxide is produced? [Molar volume:
24 dm mol at room conditions]
3
-1
In calculations, make sure that the volume of gas and
molar volume are of the same unit, which means that Solution
3
both are in cm or both are in dm . The changing of The volume of carbon dioxide gas = 100 cm 3
3
unit is as follows . 100
1 dm = 1000 cm 3 = 1000 dm = 0.1 dm 3
3
3
The number of moles of carbon dioxide
produced
= Volume of gas ÷ molar volume
0.1
= 24 = 0.0042 mol

Number moles, number of particles, mass and volume
1. The following shows the relationships between all quantities of chemicals.
÷ N × Molar mass
of
Number
Number of A Bilangan mol Mass
particles × N A moles ÷ Molar mass
× Molar volume ÷ Molar volume Number
of moles
Volume of gas calculation
VIDEO

2. Number of moles is the intermediate unit to convert other quantities of chemicals such as number of
particles, mass and volume. See the examples below.

Table 3.4 Examples of conversion of quantity of chemicals
Conversion Calculation steps
From number of particles to mass Number of particles → number of moles → mass (see Example 3.13)
From mass to volume of gas Mass → number of moles → volume of gas (see Example 3.14)
From volume of gas to number of particles Volume of gas → number of moles → number of particles (see Example 3.15)

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