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
In which of the following processes does the entropy of the system decrease?
Answer:
Crystallisation of sucrose from solution
Entropy is a measure of disorder. Crystallisation involves the transition from a disordered liquid state to a highly ordered solid crystal lattice, resulting in a decrease in entropy. Conversely, melting, vaporisation, and rusting (which involves the formation of complex oxides and often gas consumption/expansion) generally increase the disorder or entropy of the system.
2
How does the total entropy change of a system and its surroundings behave when the system is at thermodynamic equilibrium?
Answer:
remains constant
According to the second law of thermodynamics, for a process occurring at equilibrium, the total entropy change of the universe (system plus surroundings) is zero. This implies that the total entropy remains constant, as there is no net driving force for further change in the system.
3
Which type of system only allows energy exchange with its surroundings?
Answer:
Closed system
A closed system is one where only energy, not matter, can be exchanged with the surroundings. This distinguishes it from an open system, which allows both energy and matter to flow, and an isolated system, which allows no exchange of energy or matter.
4
What material is the anode typically made of in alkaline batteries?
Answer:
Zn
In alkaline batteries, the anode is usually made of zinc (Zn) due to its high reactivity with the alkaline electrolyte, allowing for efficient energy transfer and generation of electricity.
5
Planks theory says energy is emitted__________________?
Answer:
Discontinuous manner
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6
What substance is commonly used in cancer therapy?
Answer:
Co
Cobalt-60 is a radioactive isotope used in cancer therapy due to its high energy radiation, which helps in destroying cancer cells. This makes it an essential substance in the treatment of various types of cancer.
7
The Earth absorbs radiation in the visible range but emits radiation at the same rate in the form of:
Answer:
Infrared
The Earth absorbs solar radiation in the visible spectrum and then emits radiation at the same rate, but in a longer wavelength range, known as infrared radiation. This process is a fundamental aspect of Earth's energy balance and is essential for regulating global temperatures.
8
Two fundamental ways to transfer energy are________________?
Answer:
heat and work
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9
Which of the following has lowest lattice energy?
Answer:
CsI
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10
The relationship between energy of a photon of light and its frequency is given by________________?
Answer:
Plancks Quantum theory
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