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WAEC WASSCE Chemistry 2003 past questions and answers

This 2003 WAEC WASSCE Chemistry set has 40 practice questions. Try these 5 free sample questions, tap a question to reveal the answer and explanation. Then practise the whole 2003 set with instant marking.

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Sample WAEC WASSCE Chemistry 2003 questions

1. What is the electron arrangement of a chlorine atom with atomic number 17?
  1. 2,7,8
  2. 2,8,7
  3. 2,8,8
  4. 2,8,6

Answer: B. 2,8,7

The 17 electrons occupy shells as 2, 8 and 7.

2. An element consists of 75% of an isotope of mass 24 and 25% of an isotope of mass 26. What is its relative atomic mass?
  1. 24.0
  2. 24.2
  3. 24.5
  4. 25.0

Answer: C. 24.5

The weighted mean is (0.75 x 24) + (0.25 x 26) = 24.5.

3. Why does solid sugar fail to conduct electricity?
  1. It has no mobile charged particles
  2. It contains only positive ions
  3. Its molecules contain free electrons
  4. It is made of metal atoms

Answer: A. It has no mobile charged particles

Sugar is a molecular covalent solid without mobile ions or delocalized electrons.

4. Why does the reactivity of Group 1 metals generally increase down the group?
  1. Their atoms become smaller
  2. Their first ionization energies increase
  3. Their outer electrons become more strongly attracted
  4. Their outer electron is farther from the nucleus and easier to remove

Answer: D. Their outer electron is farther from the nucleus and easier to remove

Down the group, increased shielding and atomic size make the outer electron easier to remove.

5. At room temperature and pressure, what volume is occupied by 0.25 mol of an ideal gas if the molar gas volume is 24 dm3 mol-1?
  1. 3 dm3
  2. 6 dm3
  3. 12 dm3
  4. 24 dm3

Answer: B. 6 dm3

The volume is 0.25 x 24 = 6 dm3.

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