Chemistry Past Questions and Answers

A piece of sea shell, when dropped into a dilute solution of hydrochloric acid, produces a colourless, odourless gas which turns clear limewater milky. The sea shell contains

A Sodium chloride
B Ammonium nitrate
C Calcium carbonate
D Calcium chloride
E Magnesium chloride

Question 37:

Which of the following electrodes is used in electrolysis of bauxite (Al₂O₃) in molten cryolite?

A Steel electrodes
B Carbon electrodes
C Mercury electrodes
D Carbon anode and steel cathode
E Carbon cathode and stell anode

Question 38:

An aqueous solution of a metal salt, M, gives a white precipitate with NaOH which dissolves in excess NaOH. With aqueous ammonia, the solution of M also gives a white precipitate which dissolves in excess ammonia. Therefore cartion in M is

A Zn ⁺⁺
B Ca⁺⁺
C Ai⁺⁺⁺
D Pb⁺⁺
E Cu⁺⁺

Question 39:

At S. T. P how many litres of hydrogen can be obtained from the reaction of 500 cm³ of 0.5 M H ₂SO ₄ with excess zinc metal?
(Gram molecular volume of H₂ = 22. 4 dm ³)

A 22.4 dm ³
B 11 . 2 dm ³
C 6. 5 dm ³
D 5. 6 dm ³
E 0. 00 dm ³

Question 40:

The solubility curves of four substances are shown in the figure above. Which of the four substances would crystallize from a saturated solution cooled from 353K(80^oC)to 323K(50[sup][/sup]C)?

A P and Q
B P and R
C P and S
D R and S
E Q and R