18. Rita was doing and activity, she observed that when crystals of copper sulphate are strongly heated the colour of copper sulphate changes from Blue to White. Why does so happen?
(A) Due to photodecomposition of copper sulphate.
(B) Due to loss of water molecules from Copper sulphate,
(C) Due to oxidation of Copper sulphate,
(D) Due to thermal decomposition of copper sulphate
19. If a few drops of a concentrated acid accidentally spill over the hand of a student, what should be done?
(A) Wash the hand with saline solution.
(B) Wash the hand immediately with plenty of water and apply a paste of sodium hydrogen carbonate.
(C) After washing with plenty of water and apply solution of sodium hydroxide on the hand.
(D) Neutralize the acid with a strong alkali.
20. Given below is the figure of stomata. Select the correct labeling for the diagram.
(A) 1 Epidermal cell, 2 Stoma, 3 Guard cell, 4 Chloroplast
(B) 1 Guard cells, 2 Stoma, 3 Epidermal cells, 4 Chloroplast
(C) 1 Stoma, 2 Epidermal cells, 3 Chloroplast, 4 Guard cell
(D) 1 Chloroplast, 2 Stoma, 3 Epidermal cells, 4 Guard cell
Answers
Answer:
18. c
20.d
19 a
answer is this if something is wrong sorry
18 (C) Due to oxidation of Copper sulphate,
19 (A) Wash the hand with saline solution.
20 (D) 1 Chloroplast, 2 Stoma, 3 Epidermal cells, 4 Guard cell
Due to the presence of water during crystallisation, copper sulphate crystals are blue in colour. The colour is only present due to the presence of crystallisation water.
When they are heated, anhydrous copper sulphate, which is white in colour, is created (colorless). This is due to the elimination of water from the crystallisation process.
When copper sulphate crystals are heated to a high temperature, what do you see?
The colour of copper sulphate crystals changes from blue to white when heated. The boiling tube's walls are covered in water droplets. White copper sulphate becomes blue when a few drops of water are added.