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SS1: CHEMISTRY - 1ST TERM

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  1. Introduction to Chemistry and Laboratory Apparatus | Week 1
    5Topics
    |
    1 Quiz
  2. Nature of Matter | Week 2
    3Topics
    |
    1 Quiz
  3. Separation Techniques I | Week 3
    1Topic
    |
    1 Quiz
  4. Separation Techniques II | Week 4
    5Topics
    |
    1 Quiz
  5. Particulate Nature of Matter I | Week 5
    5Topics
    |
    1 Quiz
  6. Particulate Nature of Matter II | Week 6
    9Topics
    |
    1 Quiz
  7. Symbols, Formulae & Oxidation Number | Week 7
    7Topics
    |
    1 Quiz
  8. Laws of Chemical Combination | Week 8
    4Topics
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    1 Quiz
  9. Chemical Equation & Chemical Combination (Chemical Bonding) I | Week 9
    4Topics
    |
    1 Quiz
  10. Chemical Combination (Chemical Bonding) II | Week 10
    4Topics
    |
    1 Quiz
  11. Chemical Combination (Chemical Bonding) III & Shapes of Covalent Molecules | Week 11
    3Topics
    |
    1 Quiz
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The vapour density of a gas is the number of times a given volume of the gas is as heavy as the same volume of hydrogen at a particular temperature and pressure. Since vapour density is a ratio of gas volume, it has no unit. It is related to the relative molecular mass by the formula.

Relative molecular mass = 2 x vapour density mass

Or

Vapour density = \( \frac{1}{2} \scriptsize \: \times \: Relative \: molecular \: mass \)

Example 1

Calculate the vapour density of sulphur (iv) oxide (SO2) (S =32, O = 16)

Solution:

Molar mass of SO2 = 32 + 16 x 2 = 64

Vapour density = \( \frac{1}{2} \scriptsize \: \times \: Relative \: molecular \: mass \)

VD = \( \frac{64}{2} \)

VD = 32

Example 2

If 400cm3 of a certain gas weigh 0.5g at s.t.p. Calculate

(a) Molar mass

(b) Vapour density

Solution:

(a) Molar volume of gas at stp = 22.4dm3

      If 400cm3 of the gas weighs 0.5g at stp

      22400cm3 of the gas will weigh

:- \( \frac{22400}{400} \: \times \: \frac{0.5g}{1}\\ = \scriptsize 28.0g/mol \)

 (b) To calculate the vapour density.

      Vapour density = \( \frac{1}{2} \scriptsize \: \times \: molar \: mass\)

      = \( \frac{1}{2}\scriptsize \: \times \: 28 = 14.0\)

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