In order to study the properties of HCl acid, a student add dilute HCl to a test tube containing a compound X.  As a result A colourless and odourless gas is evolved, which turns the lime water milky. What could be the compound X ?Name the gas formed. What would happen on passing the gas in excess of lime water?

Asked by pdcavita | 28th Dec, 2017, 08:29: PM

Expert Answer:

Dilute HCl on reaction with metallic carbonates liberates carbon dioxide gas, 
which is colourless, odourless gas which turns lime water milky.

CaCO subscript 3 space space space plus space space space 2 HCl space space space rightwards arrow space space space space CaCl subscript 2 space space space plus space space straight H subscript 2 straight O space space space plus space space CO subscript 2 space end subscript upwards arrow space space
The compound 'X' is calcium carbonate. 
The gas formed is carbon dioxide.
When carbon dioxide is passed through lime water, it turns lime water milky due to formation of CaCO3.
But if excess of CO2 is passed through lime water then water soluble calcium bicarbonate will formed and  solution remains clear.

Answered by Varsha | 29th Dec, 2017, 11:13: AM