Question

Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.
(a) How will she find the nature of the gas ?
(b) Write down word equations of all the reactions taking place in this process.
NCERT Class VIII
Science - Main Course Book
Chapter 4. Materials: Metals and Non-metals

Answer 1

The gas thus evolved is CO2. 
To find the nature of gas evolved, 
1. CO2 has no color or smell.
2. In the presence of CO2 the burning splint will stop burning.
3. CO2 will turn moist litmus paper from blue to red, and moist universal indicator paper to yellow.
Specific tests:
1.CO2 will tun lime water milky.
Lime water is the solution of calcium hydroxide.

Calcium Hydroxide + Carbon Dioxide= Calcium carbonate+ water
Ca(OH)(aq)           +    CO2(g)         =CaCO3(s)               +H2O(l)

Answer 2

a). Charcoal burns in

oxygen to give CO² .

This gas turns moist

blue litmus red. So this

has is acidic in nature. If

this has is passed

through clear lime

water, it turns the lime

water milky.

b). i). Carbon + oxygen =

carbon dioxide

C + 0² = CO²

ii). Carbon dioxide +

water = carbonic

acid

CO² + H²O = H²CO³

iii). CO² + Ca(OH)²

=. CaCO³ + H²O