Q9 of 30 Page 1

An aqueous solution 'A' turns phenolphthalein solution pink. On addition of an aqueous solution 'B' to 'A, the pink colour disappears. The following statement is true for solution 'A' and 'B'.

Phenolphthalein is often used as an indicator in acid–base titrations. For this application, it turns colourless in acidic solutions and pink in basic solutions.

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The sky appears dark to passengers flying at very high altitudes mainly because :

 8

An element ‘X’ is forming an acidic oxide. Its position in modern periodic table will be

A. Group 1 and Period 3


B. Group 2 and Period 3


C. Group 13 and Period 8


D. Group 16 and Period 3


OR


Consider the following statements about an element ‘X’ with number of protons 13.


(A) It forms amphoteric oxide


(B) Its valency is three


(C) The formula of its chloride in XCl3


The correct statements(a) is/are


A. only (A) B. only (B)


C. (A) and (c) D. (A),(B) and (C)


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In which of the following, the identity of initial substance remains unchanged?

 11

Several factories were pouring their wastes in rivers A and B. Water samples were collected from these two rivers. It was observed that sample collected from river A was acidic while that of river B was basic. The factories located near A and B are