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
Why is the freezer compartment of a refrigerator typically positioned at the top of the unit?
Answer:
it facilitates convection currents
The placement of the freezer at the top utilizes the principle of convection. Cold air is denser than warm air and naturally sinks. By cooling the air at the top, the cold air flows downward, cooling the rest of the refrigerator compartment, while warmer air rises to be cooled by the freezer, creating an efficient circulation cycle that maintains a uniform temperature.
2
The uncertainty in the momentum (Δpx) of the particle in its lowest energy state is
Answer:
$$\Delta {p_x} = \frac{h}{a}$$
Source answer preserved: option B ($$\Delta {p_x} = \frac{h}{a}$$). AI attempted to change protected answer data (option_a), so this item is flagged for manual review before study use.
3
As per the uncertainty principle, $$\Delta x \cdot \Delta p$$ equals to
Answer:
$$\frac{h}{2}$$
Source answer preserved: option B ($$\frac{h}{2}$$). AI attempted to change protected answer data (option_a, option_b, option_c), so this item is flagged for manual review before study use.
4
Which principle contradicts Bohr's model?
Answer:
Heisenbergs uncertainty principle
Bohr's model of the atom is contradicted by Heisenberg's Uncertainty Principle, which was later developed in quantum mechanics. Plank's theory and the dual nature of matter are also important concepts in quantum mechanics, but they do not directly conflict with Bohr's model. "All of these" would be the correct answer if the principles were conflicting with Bohr's model, but in reality, they are complementary explanations in the field of quantum mechanics.
5
What is the primary cause of a spectrum being produced?
Answer:
Variation in wavelengths
A spectrum is produced due to the different wavelengths of light being refracted or dispersed at slightly different angles, resulting in a band of colours. This is a fundamental principle in optics, where the varying wavelengths correspond to different colours.