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 compound undergoes hydrolysis in the presence of an acid or base to yield an alcohol and a carboxylic acid?
Answer:
ester
Esters are chemical compounds derived from an acid and an alcohol. Through the process of hydrolysis, which is catalyzed by either an acid or a base, the ester bond is cleaved. This reaction regenerates the original carboxylic acid and the alcohol from which the ester was synthesized. This is a fundamental reaction in organic chemistry known as saponification when performed with a base.
2
Which of the following pairs of organic acids and their natural sources is incorrectly matched?
Answer:
Ascorbic acid ⟺ Tamarind
Ascorbic acid (Vitamin C) is typically found in citrus fruits, whereas tamarind primarily contains tartaric acid. Therefore, the pairing in option A is incorrect. The other options correctly identify the primary organic acids found in those specific substances.
3
What is the primary chemical compound responsible for the acidity and characteristic properties of vinegar?
Answer:
Ethanoic acid
Vinegar is essentially a dilute solution of acetic acid, which is systematically named ethanoic acid (CH3COOH). It is produced through the fermentation of ethanol by acetic acid bacteria. While other trace compounds exist, ethanoic acid is the dominant component.
4
Which organic acid is primarily found in ripe bananas?
Answer:
Malic acid
Ripe bananas contain several organic acids, with malic acid being one of the primary contributors to their flavor profile. While citric acid is also present, malic acid is widely recognized as a significant component of the fruit's acidity.
5
Which organic acid is naturally present in curd?
Answer:
lactic acid
Curd is produced through the fermentation of milk by lactic acid bacteria, such as Lactobacillus. These bacteria convert the lactose sugar present in milk into lactic acid. This process lowers the pH of the milk, causing the milk proteins to coagulate and form the semi-solid texture characteristic of curd.
6
Which class of chemical compounds is commonly utilized in the production of fragrances?
Answer:
ester
Esters are widely known for their pleasant, fruity odors. Because of this characteristic, they are extensively used in the perfume and food flavoring industries to mimic natural scents. Many naturally occurring fragrances in flowers and fruits are composed of various ester molecules, making them the standard choice for synthetic fragrance production.
7
Which class of organic compounds is typically characterized by a pleasant, fruity odor?
Answer:
Ester
Esters are organic compounds formed by the reaction of a carboxylic acid with an alcohol. Many low-molecular-weight esters possess distinct, pleasant, and fruity aromas, which is why they are widely used in the food and perfume industries as flavoring agents and fragrances.
8
Which chemical substance is commonly used to effectively remove rust stains from fabrics?
Answer:
Oxalic acid solution
Oxalic acid is effective at removing rust stains because it reacts with iron(III) oxide (rust) to form a soluble iron-oxalate complex. This complex can then be easily washed away from the fabric fibers, making it a standard reagent for stain removal in laundry and textile cleaning applications.
9
Which of the following chemical compounds does not possess a carboxylic acid functional group (-COOH)?
Answer:
Picric acid
Picric acid is 2,4,6-trinitrophenol. Despite its name, it is a phenol derivative, not a carboxylic acid. Its acidity arises from the strong electron-withdrawing effect of the three nitro groups attached to the benzene ring, which stabilizes the phenoxide ion. In contrast, vinegar (acetic acid), salicylic acid, and benzoic acid all contain the -COOH functional group.
10
Which acid is responsible for the stinging sensation in ant bites?
Answer:
Formic acid
Formic acid, or methanoic acid, is the simplest carboxylic acid. It is naturally produced by various insects, including ants, and is injected into the skin during a bite or sting, causing irritation and pain due to its acidic nature.