(a) Explain briefly the observations in each of the following processes:

(i) when carbon (IV) oxide is bubbled through lime water, It turns milky but the milkiness disappears when the gas is bubbled for a long time.

(ii) A precipitate of calcium hydroxide is insoluble in excess sodium hydroxide solution whereas that of lead (ii) hydroxide is soluble 

 

(b)(i) What is a primary standard solution?

(ii) Calculate the mass of sodium trioxocarbonate (V) required to prepare 250 cm\(^3\) of 0.15gmoldm\(^3\) solution hydroxide is soluble.  [Na = 23.0; O = 16.0; C = 12.0] 

 

(c) Name one gas that can be collected by 

(i) upward displacement of air 

(ii) downward displacement of air