PassSparkWAEC WASSCE Chemistry 2017 past questions and answers
This 2017 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 2017 set with instant marking.
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Sample WAEC WASSCE Chemistry 2017 questions
1. Which method is most suitable for obtaining pure water from a sample of seawater?
- Simple distillation
- Filtration
- Decantation
- Paper chromatography
Answer: A. Simple distillation
On heating, water vaporizes and can be condensed separately from the dissolved salts.
2. An atom has atomic number 17 and mass number 37; how many neutrons are in its nucleus?
- 17
- 20
- 37
- 54
Answer: B. 20
The number of neutrons is the mass number minus the atomic number, giving 37 - 17 = 20.
3. Chlorine consists of 75% chlorine-35 and 25% chlorine-37; what is its relative atomic mass?
- 35.0
- 34.5
- 35.5
- 36.0
Answer: C. 35.5
The weighted mean is (0.75 x 35) + (0.25 x 37) = 35.5.
4. What is the electron arrangement of an oxide ion, O2-, given that oxygen has atomic number 8?
- 2,6
- 2,7
- 2,8,2
- 2,8
Answer: D. 2,8
An oxide ion has gained two electrons, so it has 10 electrons arranged as 2,8.
5. What happens to the atomic radius generally as elements are considered from left to right across Period 3?
- It decreases
- It increases
- It remains constant
- It first increases and then remains constant
Answer: A. It decreases
Increasing nuclear charge across the period attracts the electron shells more strongly without adding a new shell.
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