Carbondioxide Gas
* Laboratory method of preparation of CO2 gas.
CaCO3+dil2HCL ® CaCl2 +H2O+CO2
* Industrial preparation of CO2 gas.
CaCO3 ®CaO+CO2
* When passes into lime water for some time then lime water becomes milky. But the colour disappears if CO2 is passed for longer time.
Ca(OH)2 +CO2 ® CaCO3+H2O
CaCo3+H2O+ CO2® Ca(HCO3)2
* Used of CO2 Gas.
– In the manufacture of soft drinks
– As five extinguishes
– When it is cooked to -78OC then changes to white solid form called dry ice.
– Used for the manufacture of urea.
– Used by plants during photosynthesis.
* Laboratory preparation of NH3 gas.
2NH4Cl+Ca(OH)2®CaCl2+2H2O +2NH3
* Uses of ammonia gas:
– Used in the manufacture of chemical fertilizer.
– Used for developing blue prints of maps.
– Used as cleansing agent
– Used for the manufacture of nitric acid, explosives, plastics etc.
REASONABLE FACTS
1. A moist red litmus paper is used to test the ammonia gas.
Ans- Ammonium hydroxide is an alkali. So a wet litmus paper is used to test the gas whether it is ammonia or not. If the gas is ammonia, it reacts with wet litmus paper and forms ammonium hydroxide that changes the litmus into blue colour.
2. The mouth of hard glass test tube is slightly slanted during the preparation of ammonia gas.
Ans- During the preparation of ammonia gas, the mixture of ammonium chloride and calcium forms steam and reaches at the upper end of the test tube and later liquefies that may come back at the bottom of the test tube. It may cause cracking of the test tube. So the hard glass test tube is slightly slanted to prevent the glass tube from cracking.
OR
The month of hard glass test tube is slightly slanted during the preparation of ammonia gas because for the following reasons:
– To avoid the water drops which flow down if the test tube is not inclined.
– To prevent from cracking of test tube.
3. Ammonia gas is not collected over water.
Ans- Ammonia gas is highly soluble in water. One volume of water dissolves 100 volumes of ammonia gas. Hence, ammonia gas is not collected over water.
4. Ammonia gas is not collected in the gas jar by upward displacement of air.
Ans- Ammonia gas is not collected in the gas jar by upward displacement of air because it is lighter than air.
5. Ammonia gas cannot be collected in the gas jar either by the downward displacement of water or upward displacement of air.
Ans- Ammonia gas cannot be collected in the gas jar either by the downward displacement of water because this gas is highly soluble in water and forms ammonium hydroxide when passed in water. But this gas is also lighter than air so it cannot be collected in the gas jar by the upward displacement of air.
6. Ammonia solution is alkaline in nature.
Ans-Ammonia solution is alkaline in nature because it turns red litmus into blue.
7. The sulphuric acid is placed in a glass bottle.
Ans- Because of the following reasons:
– A glass bottle can break easily when the knob is pressed down.
– It is not eroded by acid.
8. The sulphuric acid is placed in a glass vessel in a fire extinguisher.
Ans- The sulphuric acid is placed in a glass vessel in a fire extinguisher because glass vessel is not eroded by sulphuric acid.
9. CO2 gas is used in the fire extinguisher because of the following reasons:
– It is neither combustible gas nor supporter of combustion
– It is heavier than air so it covers the fire as a blanket and the fuel does not burn in the absence of oxygen.
10. Carbon dioxide is not collected in a gas jar containing water.
Ans- Carbon dioxide is not collected in a gas jar containing water because it is soluble in water and forms carbonic acid.
11. Bubbles come out when a soda water bottle is opened.
Ans- Bubbles come out when a soda water bottle is opened because in the manufacture of soda water, CO2 is dissolved at extreme pressure. When the lid of soda water is opened the pressure reduces and carbon dioxide liberates out from the soda water in the form of bubbles.
12. If moist litmus paper is introduced into the CO2 gas filled jar, it turns into red.
Ans- If moist litmus paper is introduced into the CO2 gas filled jar, it turns into red because the CO2 gas is acidic gas.
13. NaOH solution is used to separate the CO2 gas from the mixture but Ca(OH)2 is used to test CO2 gas.
Ans- Since NaOH absorbs CO2 gas but Ca(OH)2 turns into milky colour. Hence, NaOH solution is used to separate the CO2 gas from the mixture but Ca(OH)2 is used to test CO2 gas.
14. CO2 gas cannot be collected by downward displacement of water.
Ans- CO2 gas is about 1.5 times heavier than air and highly soluble is water. So it is collected by upward displacement of air.
15. CO2 gas is found in deep wells, mines and caves.
Ans- CO2 gas is about 1.5 times heavier than air so can be found in caves and mines and it is also highly soluble in water so can be found in deep wells.
16. CO2 gas does not burn in air and does not support combustion but burning magnesium
ribbon burns in it.
Ans- Mg is a strong electropositive element. Thus, it retains oxygen from CO2 at high temperature at high temperature. Hence, Magnesium burns in CO2 gas.
17. CO2 gas is not prepared by reaction of limestone and sulphuric acid in lab.
Ans- It is because when limestone reacts with sulphuric acid calcium sulphate is formed which covers the entire surface of limestone and prevents from the further reaction and formation of CO2 gas stops.
