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
41
Which chemical compound is primarily responsible for the irritation caused by an ant's sting?
Answer:
Formic acid
Ant stings, particularly from certain species like Formicidae, inject a venom that contains formic acid (methanoic acid). This organic acid is responsible for the pain, redness, and swelling experienced at the site of the sting. The name 'formic' is derived from the Latin word 'formica', meaning ant.
42
Which of the following compounds conducts electricity in water and forms a basic solution?
Answer:
NaOH
Sodium hydroxide (NaOH) is a strong base that dissociates completely in water into Na+ and OH- ions. The presence of free ions allows the solution to conduct electricity, and the high concentration of hydroxide ions makes the solution basic.
43
What are the primary products formed during the neutralization reaction between an acid and an alkali?
Answer:
Salts and water
Neutralization is a chemical reaction in which an acid and a base react quantitatively with each other. In an aqueous solution, the H+ ions from the acid react with the OH- ions from the base to produce water (H2O), and the remaining cation and anion form an ionic salt.
44
What is the nature of soda water, which is produced by dissolving carbon dioxide in water?
Answer:
acidic in nature
When carbon dioxide (CO2) dissolves in water, it reacts to form carbonic acid (H2CO3). This weak acid dissociates slightly in water, lowering the pH of the solution. Consequently, soda water is acidic in nature, which contributes to its characteristic sharp, tangy taste.
45
Which substance is typically applied to treat the site of a bee sting?
Answer:
Baking soda
Bee venom is acidic in nature. Baking soda (sodium bicarbonate) is a mild base that helps neutralize the acid, thereby providing relief from the pain and irritation caused by the sting.
46
What is the general chemical equation representing a neutralization reaction between an alkali and an acid?
Answer:
Alkali + acid ⟶ salt + water
A neutralization reaction occurs when an acid reacts with a base (alkali) to produce a salt and water. The hydrogen ions from the acid combine with the hydroxide ions from the base to form water molecules, effectively neutralizing the acidic and basic properties.
47
What is the chemical composition of milk of magnesia?
Answer:
magnesium hydroxide
Milk of magnesia is a suspension of magnesium hydroxide, Mg(OH)2, in water. It is commonly used as an antacid to neutralize excess stomach acid because it is a mild base. When ingested, it reacts with hydrochloric acid in the stomach to form magnesium chloride and water, thereby relieving heartburn and indigestion.
48
Which of the following characteristics is NOT true regarding alkalis?
Answer:
Sour in taste
Alkalis are basic in nature and are characterized by a bitter, astringent taste and a soapy, slippery feel when touched. They are known to be corrosive to skin and materials. Sour taste is a defining characteristic of acids, not alkalis (bases). Therefore, stating that alkalis are sour is factually incorrect.
49
Which of the following substances will not produce carbon dioxide when it reacts with an aqueous solution of hydrochloric acid?
Answer:
Quicklime
Limestone, chalk, and marble are all forms of calcium carbonate (CaCO3), which reacts with HCl to release CO2. Quicklime is calcium oxide (CaO). When CaO reacts with HCl, it undergoes a neutralization reaction to form calcium chloride (CaCl2) and water (H2O), but it does not produce carbon dioxide gas.
50
What is the common scientific name for the substance known as muriatic acid?
Answer:
Hydrochloric Acid
Muriatic acid is a historical and industrial name for hydrochloric acid (HCl). It is commonly sold in hardware stores for cleaning masonry, adjusting the pH of swimming pools, and various other industrial cleaning applications. The term 'muriatic' is derived from the Latin word 'muria', meaning brine or salt.