Chemistry MCQs
Topic Notes: Chemistry
MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.
Plato
- Biography: Ancient Greek philosopher (427–347 BCE), student of Socrates and teacher of Aristotle, founder of the Academy in Athens.
- Important Ideas:
- Theory of Forms
- Philosopher-King
- Ideal State
1
What is the entropy value of a perfectly crystalline solid at absolute zero temperature?
Answer:
Zero
According to the Third Law of Thermodynamics, the entropy of a perfect crystal at absolute zero (0 Kelvin) is exactly zero. This is because there is only one possible microstate for a perfectly ordered system at this temperature, resulting in no positional or thermal disorder.
2
At absolute zero, which physical property of an ideal gas becomes zero?
Answer:
Kinetic energy
According to the kinetic molecular theory, the average kinetic energy of gas particles is directly proportional to the absolute temperature (K). At absolute zero (0 K), the motion of gas particles theoretically ceases, resulting in zero kinetic energy.
3
What is the approximate value of absolute zero, the theoretical temperature limit?
Answer:
-273°C
Absolute zero is defined as 0 Kelvin, which corresponds to approximately -273.15 degrees Celsius. At this temperature, the thermodynamic system has the lowest possible energy, and all classical molecular motion ceases.
4
What fraction of the solar flux absorbed by the Earth's surface is utilized to power the hydrologic cycle?
Answer:
1/3rd
The Earth's surface absorbs solar flux, a significant portion of which drives the hydrologic cycle, involving evaporation, condensation, and precipitation. Approximately one-third of this absorbed flux is used for this purpose, influencing global climate and weather patterns.
5
If the volume of a given mass of gas at constant temperature triples, what happens to the pressure?
Answer:
P/3
According to Boyle's Law, at constant temperature, pressure and volume are inversely proportional. If volume triples, pressure becomes one-third. Thus, if the original pressure is P and the original volume is V, when V becomes 3V, the pressure becomes P/3.
6
What will be the effect of reaching absolute zero on gas diffusion?
Answer:
Zero
At absolute zero, the diffusion of gases reaches its lowest possible point. According to the Third Law of Thermodynamics, all thermal vibrations of molecules cease at absolute zero. This means that even though the temperature is 0 Kelvin, the gas molecules still do not have any kinetic energy to move or diffuse. Therefore, the diffusion of gases will be zero at absolute zero.
7
Which of the following is the Third layer of atmosphere as one moves upwards from the Earth's surface?
Answer:
mesosphere
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