Which natural indicator (acid-base) is used in kitchens of our homes?

(1) Sodium chloride
(2) Tea leaves
(3) Sodium carbonate
(4) Turmeric

Copper sulphate solution is electrolysed with platinum electrodes. Which of the following changes does not occur in the process?

(1) The blue colour of the solution gradually fades 
(2) O₂(g) is liberated at anode 
(3) pH of the solution decreases 
(4) H⁺ concentration decreases

The concentration of hydroxide ion in a solution is 1 × 10^–10 mole per litre. Its pH value will be:

(1) 4
(2) 8
(3) 10
(4) –10

The compound containing both covalent and ionic bond is

(1) MgCl₂
(2) NH₄Cl
(3) CaO
(4) AlBr₃

Which of the following does not form salt with alkali but forms with acid?

(1) BeO
(2) ZnO
(3) CaO
(4) SnO