Practise 45 real Federal Board questions on Environmental Chemistry (Atmosphere / Water) from 2023 to 2025. See the answer and explanation as soon as you answer.
Environmental Chemistry (Atmosphere / Water) is one of the 11 main chapters in our Federal Board Matric Chemistry question bank (10th class), and about 13% of its real questions come from it. Tayyari Karo has 45 real questions on this chapter from 2023 to 2025; 13 are multiple choice and marked instantly, and the rest are short and long questions with a model answer. By difficulty: 26 easy, 19 medium.
Work through the questions below, then open the explanation for each one. Redo the ones you missed a few days later.
These are real past-paper questions. Think of your answer first, then open the explanation.
The envelop of gases and water vapours, surrounding the planet earth is called:
Answer: A. Atmosphere
The atmosphere is the overall envelope of gases surrounding the Earth, of which troposphere, stratosphere and mesosphere are individual layers.
Which statement about water is correct?
Answer: D. Boils at 100°C
Water boils at 100°C at standard atmospheric pressure; the other statements are false — water actually has a high heat capacity, high heat of vaporization, and expands (not contracts) when it freezes.
What type of impurity causes temporary hardness in water?
Answer: D. Ca(HCO₃)₂
Temporary hardness is caused by dissolved bicarbonates of calcium and magnesium, such as Ca(HCO₃)₂, which can be removed simply by boiling.
The percentage of Nitrogen in the air is:
Answer: C. 78%
Clean, dry air is approximately 78% nitrogen by volume.
The density of water is maximum at:
Answer: B. 4°C
Water shows anomalous expansion and has its maximum density at 4°C, which is why ice (formed below 0°C) floats on liquid water.
Water is used as an excellent cooler (coolant) in industries because of its:
Answer: C. High heat capacity
Water has an unusually high specific heat capacity, so it can absorb large amounts of heat with only a small rise in its own temperature, making it an excellent coolant.
Water has maximum density at 4°C. How does it help the aquatic life to survive in winter?
In winter, as the surface water cools below 4°C, it becomes less dense (due to water's anomalous expansion on cooling below 4°C) and stays on top, eventually freezing into ice at the surface. Since ice is less dense than water, it floats and forms an insulating layer on top, while the water below (at around 4°C, its densest state) remains liquid. This allows fish and other aquatic organisms to survive in the liquid water below the ice layer even when the surface is frozen.
Explain the process of ozone formation and degradation in stratosphere. Discuss the role of ultraviolet radiations in this process as well.
Ozone formation: High-energy UV radiation splits molecular oxygen into individual oxygen atoms: O₂ --(UV)--> O + O. Each oxygen atom then combines with another O₂ molecule to form ozone: O + O₂ → O₃.
Ozone degradation: Ozone itself absorbs UV radiation and breaks back down into O₂ and an oxygen atom: O₃ --(UV)--> O₂ + O.
Role of UV radiation: UV radiation drives both the formation and degradation reactions, creating a continuous, dynamic equilibrium (ozone-oxygen cycle) that keeps the overall ozone concentration roughly constant in the stratosphere over time, while simultaneously absorbing most of the sun's harmful UV rays and protecting life on Earth's surface.
| Session | Questions |
|---|---|
| 2025 1st Annual | 11 |
| 2025 2nd Annual | 11 |
| 2024 Annual | 14 |
| 2023 Annual | 9 |
45 real Federal Board (FBISE) Chemistry questions on Environmental Chemistry (Atmosphere / Water) from 2023 to 2025, for 10th class. Each one shows the session it came from.
No. We could not find an official FBISE marking scheme for these papers, so the answers and explanations are written by Tayyari Karo for practice. Check anything important with your teacher or textbook.
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