Cbse '- Class X - Science Worksheet - Byju'S, 2013 Page 5
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11(B) II, III and IV
(C) III, IV and I
(D) I, II and IV
Q28 Read the following statements: (1)
I.
When a red litmus paper is dipped into reaction mixture of a saponification reaction, it turns
blue and the reaction is exothermic.
II.
When a blue litmus paper is dipped into reaction mixture of a saponification reaction, its
colour does not change and the reaction is exothermic.
III.
When a red litmus paper is dipped into reaction mixture of a saponification reaction, its
colour does not change and the reaction is endothermic.
IV.
When a blue litmus paper is dipped into reaction mixture of a saponification reaction, its
colour does not change and the reaction is endothermic.
Which of the above statements are correct?
(A) I and II
(B) II and III
(C) III and IV
(D) I and IV
Q29 Hard water required for an experiment is not available in a school laboratory. However,
following salts are available in the laboratory. Select the salts which may be dissolved in water to
make it hard for the experiment. (1)
(1) Calcium Sulphate
(2) Sodium Sulphate
(3) Calcium Chloride
(4) Potassium Sulphate
(5) Sodium Hydrogen Carbonate
(6) Magnesium Chloride
(A) 1, 2 and 4
(B) 1,3 and 6
(C) 3,5 and 6
(D) 2,4 and 5
Q30 A student focused the image of a distant object using a device ‘X’ on a while screen ‘S’ as shown
in the figure. If the distance of the screen from the device is 40 cm, select the correct statement
about the device. (1)
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