Assertion and Reason Questions and Answers

Answer: B

Correct answer: Both A and R are true but R is NOT the correct explanation of A.

Both statements are true, but the reason is too loose to be the explanation. What spoils washing is specifically the calcium and magnesium ions, which react with soap to form an insoluble scum instead of lather; other dissolved minerals do no such thing. R does not explain A.

Answer: A

Correct answer: R correctly explains A

Watt’s steam engine was developed for one industrial problem above all: pumping water out of flooded mines, which the earlier atmospheric engines did at ruinous cost in fuel. His separate condenser cut that fuel by three-quarters and made the engine practical, so R correctly explains A.

Answer: C

Correct answer: A is true but R is false

Kerosene poured on stagnant water does check malaria, so A is true. But it works mechanically: the thin film spreads over the surface and prevents the mosquito larvae from reaching air through their breathing tubes, so they suffocate. It is not acting as a poison. R is false.

Answer: D

Correct answer: R correctly explains A

Seals from Harappa and Mohenjo-daro have been found at Ur and other Mesopotamian sites, and Lothal has what is taken for a dockyard. Trade across the sea is evidence that the Indus people could navigate, so R correctly explains A.

Answer: A

Correct answer: R correctly explains A

The Himalayan rivers rise in glaciers and snowfields that melt through the summer, so they keep flowing even when the monsoon fails. Peninsular rivers, fed only by rain, run dry. R correctly explains A.

Answer: C

Correct answer: Both A and R are false.

Both statements are the wrong way round: Bangladesh is a great producer of raw jute and exports it, while it is India that holds most of the jute mills, concentrated along the Hooghly. Both A and R are false.

Answer: A

Correct answer: Both A and R are true and R is the correct explanation of A.

Watt’s engine was built for the task of draining flooded mines, and his separate condenser reduced its fuel consumption so far that the engine became commercially practical. The mining problem is precisely what drove its development. Both are true and R explains A.

Answer: A

Correct answer: Both A and R are true and R is the correct explanation of A.

Carbon dioxide traps outgoing infrared radiation, so more of it raises the global temperature - and it is warmer air and oceans that melt the polar ice. The rise in temperature is the mechanism linking the two. Both are true and R explains A.

Answer: A

Correct answer: Both A and R are true and R is the correct explanation of A.

Tamil Nadu receives most of its rain between October and December, when the retreating monsoon winds blow from the north-east across the Bay of Bengal and pick up moisture before striking the Coromandel coast. Both are true and R explains A.

Answer: B

Graphite possesses a layer structure with two successive layers held by weak force and able to slide over one another.
So, graphite is slippery and this property finds its use as a lubricant.
In graphite, each carbon atom is linked to three other carbon atoms while one electron in the carbon atom is delocalised.
So, graphite has free electrons.