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
Which of the following substances is not classified as an alkali?
Answer:
C2H5OH
An alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Ethanol (C2H5OH) is an alcohol, which is a neutral organic compound containing a hydroxyl group covalently bonded to a carbon atom, and it does not dissociate to produce hydroxide ions in water.
2
Which of the following substances is not a standard component of gastric acid secreted in the human stomach?
Answer:
sulphuric acid
Gastric juice in the human stomach primarily consists of hydrochloric acid (HCl), along with potassium chloride (KCl) and sodium chloride (NaCl). Sulphuric acid (H2SO4) is a strong mineral acid that is not produced by the human digestive system; its presence would be highly corrosive and harmful to biological tissues.
3
What is the common element present in all Arrhenius acids?
Answer:
Hydrogen
According to the Arrhenius theory, an acid is a substance that dissociates in water to produce hydrogen ions (H+). Therefore, the presence of hydrogen is a defining characteristic of all Arrhenius acids, as these ions are responsible for the acidic properties observed in aqueous solutions.
4
Which of the following statements correctly defines the properties of an acid?
Answer:
Only 1 is correct
Acids are characterized by a sour taste. However, they turn blue litmus paper red, not red to blue. Therefore, statement 1 is correct, and statement 2 is incorrect. This makes option A the correct choice. Acids are proton donors or electron pair acceptors, and their interaction with litmus is a standard diagnostic test in chemistry.
5
What is the common name for a saturated solution of calcium hydroxide?
Answer:
Lemonade
The question refers to 'Limewater', which is the common name for a saturated aqueous solution of calcium hydroxide. While the provided option 'A' is labeled 'Lemonade', this is factually incorrect as limewater is chemically distinct from lemonade. We retain the provided answer key per instructions.
6
What is the chemical nature of antacids?
Answer:
base
Antacids are substances used to neutralize excess stomach acid (hydrochloric acid). They are chemically basic compounds, such as magnesium hydroxide or aluminum hydroxide, which react with the acid to form water and salts, thereby relieving symptoms of indigestion or heartburn.
7
Sodium chloride (NaCl) is a salt formed by the reaction of which types of substances?
Answer:
Strong acid and strong base
Sodium chloride is formed through the neutralization reaction between hydrochloric acid (HCl), which is a strong acid, and sodium hydroxide (NaOH), which is a strong base. Because both reactants are strong, the resulting salt is neutral with a pH of approximately 7.
8
Which specific acid is primarily responsible for the acidity of human gastric juice?
Answer:
Hydrochloric acid
Gastric juice in the human stomach contains a significant concentration of hydrochloric acid (HCl). This acid is secreted by the parietal cells of the stomach lining and serves a critical role in digestion by denaturing proteins and activating the enzyme pepsin, while also providing a defense mechanism against ingested pathogens.
9
Evaluate the following statement: 'Sulphuric acid is acidic in nature.' Which of the provided conclusions are valid?
Answer:
Neither conclusion 1 nor 2 is correct
Sulphuric acid (H2SO4) is a strong acid, so its pH is significantly lower than 7, not 7.5. Furthermore, sulphuric acid consists of hydrogen, sulphur, and oxygen; it does not contain phosphorus. Therefore, both provided conclusions are factually incorrect regarding the properties of sulphuric acid.
10
Which acid is primarily responsible for the tart or sour taste in carbonated beverages like Coca-Cola?
Answer:
phosphoric acid
Phosphoric acid is a common additive in many colas and carbonated soft drinks. It provides a sharp, tangy, or sour flavor profile and also acts as a preservative to inhibit the growth of molds and bacteria in the sugary solution.