Air and Water Practice Questions
WAEC (West Africa) · WAEC Chemistry · 133 free MCQs with instant results and detailed explanations.
133
Total
33
Easy
71
Medium
29
Hard
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Sample Questions from Air and Water
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Q1
Easy
Which of the following is a common method for purifying drinking water?
A.
Filtration
B.
Evaporation
C.
Sublimation
D.
Condensation
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Correct Answer: A
Filtration is widely used to remove impurities and sediments from water, making it safe for drinking, unlike evaporation, sublimation, or condensation which do not effectively purify water.
Q2
Easy
What is the main gas responsible for the greenhouse effect in the atmosphere?
A.
Oxygen
B.
Carbon Dioxide
C.
Nitrogen
D.
Helium
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Correct Answer: B
Carbon Dioxide is the primary greenhouse gas that traps heat in the atmosphere, contributing significantly to global warming, unlike oxygen, nitrogen, and helium which do not have this effect.
Q3
Easy
Which of the following statements about water is true?
A.
Water is a good conductor of electricity.
B.
Water has a high specific heat capacity.
C.
Water is a non-polar molecule.
D.
Water has a higher density in its solid state than in liquid state.
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Correct Answer: B
Water has a high specific heat capacity, which means it can absorb a lot of heat before its temperature changes. This property is crucial for regulating temperatures in the environment.
Q4
Medium
Which of the following gases is primarily responsible for the greenhouse effect in the atmosphere?
A.
Carbon Dioxide
B.
Ozone
C.
Nitrogen
D.
Argon
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Correct Answer: A
Carbon Dioxide is a major greenhouse gas that traps heat in the atmosphere, contributing significantly to the greenhouse effect.
Q5
Medium
If 500 ml of a solution contains 40 g of dissolved salt, what is the concentration of the salt in grams per liter?
A.
80 g/L
B.
40 g/L
C.
20 g/L
D.
100 g/L
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Correct Answer: A
To find the concentration in g/L, convert 500 ml to liters (0.5 L) and then divide the mass of salt (40 g) by the volume in liters: 40 g / 0.5 L = 80 g/L.
Q6
Medium
Which process primarily removes carbon dioxide from the atmosphere?
A.
Photosynthesis
B.
Respiration
C.
Combustion
D.
Decomposition
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Correct Answer: A
Photosynthesis is the process by which plants absorb carbon dioxide from the atmosphere and convert it into glucose and oxygen, effectively reducing CO2 levels.
Q7
Medium
What is the main component of natural water that contributes to its hardness?
A.
Calcium Bicarbonate
B.
Sodium Chloride
C.
Potassium Nitrate
D.
Magnesium Sulfate
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Correct Answer: A
Calcium bicarbonate is a primary contributor to water hardness, as it forms when water interacts with limestone and other calcium-rich minerals.
Q8
Hard
What is the main component of dry air by volume?
A.
Oxygen
B.
Nitrogen
C.
Carbon Dioxide
D.
Argon
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Correct Answer: B
Nitrogen constitutes about 78% of dry air, making it the main component. Oxygen is about 21%, while carbon dioxide and argon are present in much smaller quantities.
Q9
Hard
A sample of water has a pH of 3. What is the concentration of hydrogen ions in the solution?
A.
1 x 10^-3 M
B.
1 x 10^-7 M
C.
1 x 10^-10 M
D.
1 x 10^-14 M
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Correct Answer: A
The pH scale is logarithmic, and a pH of 3 corresponds to a hydrogen ion concentration of 10^-3 M. This means the solution is acidic with a higher concentration of hydrogen ions.
Q10
Hard
When 2 g of sodium chloride is dissolved in 100 g of water, what is the concentration of the solution in grams per liter (g/L)?
A.
20 g/L
B.
50 g/L
C.
10 g/L
D.
25 g/L
Show Answer & Explanation
Correct Answer: A
To find the concentration in g/L, you need to convert the mass of the solute to grams and volume of the solvent to liters. Since 100 g of water is equal to 0.1 L, the concentration is 2 g / 0.1 L = 20 g/L.
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Air and Water — WAEC (West Africa) WAEC Chemistry Practice Questions Online
This page contains 133 practice MCQs for the chapter Air and Water in WAEC (West Africa) WAEC Chemistry. The questions are organized by difficulty — 33 easy, 71 medium, 29 hard — so you can choose the right level for your preparation.
Every question includes a detailed explanation to help you understand the concept, not just memorize answers. Take a timed quiz to simulate exam conditions, or practice at your own pace with no time limit.