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 a 1 kg alloy containing 32% copper and 70% zinc, what is the total mass of copper in grams?
Answer:
320 grams
The total mass of the alloy is 1 kg, which is equivalent to 1000 grams. Given that the alloy contains 32% copper by mass, the calculation is 0.32 multiplied by 1000 grams, which equals 320 grams. Note: The provided percentage for zinc (70%) is mathematically inconsistent with a 100% total, but the copper calculation remains straightforward.
2
The fact that ammonia (NH3) consistently contains the same ratio of nitrogen to hydrogen regardless of its origin supports which chemical law?
Answer:
Constant proportion
The Law of Constant Proportion (or Definite Proportions) states that a chemical compound always contains its component elements in a fixed ratio by mass, regardless of the source or method of preparation. This is a fundamental principle of stoichiometry.
3
In a mixture of salts and acids with a ratio of 5:7, what is the weight of the acid if the total mixture weighs 360 grams?
Answer:
210 gm
The total ratio parts are 5 + 7 = 12. The weight of one part is 360 / 12 = 30 grams. The acid represents 7 parts, so the weight of the acid is 7 * 30 = 210 grams.
4
Which of the following chemical properties is dependent on the valency of an element?
Answer:
Equivalent weight
Equivalent weight is defined as the molar mass of a substance divided by its valency factor (n-factor). Since the valency factor directly influences the calculation of equivalent weight, it is the property that changes based on the valency of the element in a specific reaction.