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
51
Aqua regia is a highly corrosive mixture composed of concentrated hydrochloric acid and concentrated nitric acid in what volume ratio?
Answer:
Three
Aqua regia is prepared by mixing concentrated hydrochloric acid (HCl) and concentrated nitric acid (HNO3) in a 3:1 molar ratio by volume. This mixture is famous for its ability to dissolve noble metals like gold and platinum due to the formation of nitrosyl chloride and nascent chlorine, which act as powerful oxidizing agents.
52
Which of the following statements regarding the chemical properties of acids is incorrect?
Answer:
Acids react with alkali and increase salts which is called decomposition reaction
Statement B is incorrect because the reaction between an acid and an alkali (base) is called a neutralization reaction, not a decomposition reaction. Neutralization involves the formation of salt and water. The other statements (A, C, and D) correctly describe the standard chemical reactivity of acids with metal oxides, active metals, and carbonates respectively.
53
Which organic acid is responsible for the sour taste of curd?
Answer:
acetic acid
Curd is produced by the fermentation of milk by lactic acid bacteria, primarily Lactobacillus. These bacteria convert lactose into lactic acid, which lowers the pH and gives curd its characteristic sour taste. Note: The provided answer key indicates C (acetic acid), which is factually incorrect as acetic acid is found in vinegar. Lactic acid is the correct chemical component.
54
Which of the following acids does not contain oxygen in its molecular structure?
Answer:
Hydrochloric Acid
Hydrochloric acid (HCl) is a binary acid consisting of hydrogen and chlorine, containing no oxygen atoms. In contrast, oxyacids like nitric acid (HNO3) and sulphuric acid (H2SO4) contain oxygen atoms bonded to the central atom. Therefore, HCl is the correct choice.
55
What is the chemical composition of common table salt (NaCl) in terms of its acid-base origin?
Answer:
A strong acid and a strong base
Sodium chloride (NaCl) 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 components are strong, the resulting salt is neutral in aqueous solution.
56
Which of the following statements regarding strong acids is incorrect?
Answer:
Acids are chemical substances that have a salty taste
The statement that acids have a salty taste is incorrect; acids are characterized by a sour taste. Strong acids are defined by their complete dissociation in aqueous solutions, releasing a high concentration of hydrogen ions. Common examples include HCl, H2SO4, and HNO3, which are highly reactive.
57
Identify the incorrect statement regarding acid classification and properties.
Answer:
Organic acid ⟺ obtained from chemical fertilizers
Organic acids are typically derived from biological sources (plants and animals), not chemical fertilizers. The other statements are correct: strong acids dissociate completely in water, mineral acids are often highly corrosive and dangerous, and dilute acids contain a low ratio of solute to solvent.
58
Which of the following is NOT a characteristic property of acids?
Answer:
The taste of acid is bitter
Acids are characterized by a sour taste and the ability to turn blue litmus paper red. They also react with bases (alkalis) in neutralization reactions to produce salts and water. A bitter taste is a property associated with bases (alkalis), not acids. Thus, option B is the incorrect property.
59
Any substance which accepts H+ is base favours the concept___________________?
Answer:
Lowrys
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60
Source of caproic acid is
Answer:
butter
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