UPSC Prelims 2006 · General Studies

Question 19: Science and Technology

Assertion (A): Cellulose is used in making shatter-proof glass. Reason (R): Polysaccharides are not soluble in water.

aBoth A and R are true and R is the correct explanation of A

bBoth A and R are true but R is not a correct explanation of A

cA is true but R is false

dA is false but R is true

AnswerThe answer is (a).

Laminated safety glass holds fragments together with a plastic interlayer. Early safety glass used cellulose derivatives such as cellulose acetate or nitrate for this, so the Assertion is accepted. Cellulose and most other polysaccharides are large molecules that do not dissolve in water, which helps such a film stay stable. The key treats both statements as true, with R explaining A, though that link is loose.

A. Cellulose derivatives were used in laminated safety glass.
R. Polysaccharides like cellulose are not soluble in water.

How you could have got this

If you were sure statement 1 is correct, (d) goes. Then judge the second statement; if it is correct too, decide whether it explains the first.

This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.

Which options go is worked out from UPSC’s key and the options, not by a model.

Why each option is right or wrong

(a) The given key: both are true and R is taken as the explanation.
(b) Both are true, but this treats R as unrelated to A, which the key does not.
(c) R is true, not false.
(d) A is accepted as true, not false.

Worth knowing: Arguable: modern shatter-proof glass uses polyvinyl butyral, and water-insolubility is only one reason a cellulose derivative suits it, so (b) can be defended.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2006, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.