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 most appropriate method for separating very small, insoluble particles suspended in a liquid?
Answer:
decantation
Decantation is a process used to separate mixtures by removing a liquid layer, free of a precipitate, from a solid. While centrifugation is often more effective for very fine particles, decantation is the traditional method listed here for separating settled insoluble solids from liquids.
2
Which separation technique is most effective for isolating iodine from a mixture containing potassium chloride?
Answer:
sublimation
Iodine is a substance that readily undergoes sublimation, meaning it transitions directly from a solid state to a gaseous state upon heating. Potassium chloride, an ionic salt, does not sublime at standard temperatures. By heating the mixture, iodine vaporizes and can be collected on a cool surface, leaving the non-volatile potassium chloride behind, thus effectively separating the two components.
3
Evaluate the following statements regarding mixtures: 1. A substance can be separated into other kinds of matter by any physical process. 2. Dissolved sodium chloride can be separated from water by the physical process of evaporation.
Answer:
Only 2
Statement 1 is incorrect because pure substances cannot be separated into simpler substances by physical means; only mixtures can. Statement 2 is correct because evaporation is a physical process used to separate a solute (sodium chloride) from a solvent (water) by removing the solvent through phase change, leaving the solid residue behind.
4
In a chemical compound, elements are consistently present in fixed proportions by which physical property?
Answer:
mass
The Law of Definite Proportions, or Proust's Law, states that a chemical compound always contains its constituent elements in a fixed ratio by mass, regardless of the source or method of preparation of the compound.