33 Science -- Some Gases

How does a fire extinguisher work?

1 Answers

We know, fire extinguisher has a red metallic vessel containing a sodium bicarbonate solution and a bottle of sulphuric acid. When we need carbon dioxide gas to extinguish a fire, the vessel is inverted. Afterwards, the bottle of concentrated sulpheric acid strikes against the floor. The plug of the acid bottle falls down and and comes in contact with the sodium bicarbonate solution. When those chemical react together, they give carbon dioxide gas.
2NaHCO₃ + H₂SO₄ ----------> Na₂SO₄ + 2H₂O + 2CO₂↑
The gas produced in the above reaction comes out from the nozzle at high pressure and put off the fire, just like putting a blanket over the surface of the flame.

Write down the principle of laboratory preparation of ammonia gas with a balanced chemical eqn and well labeled figure.

In the laboratory, ammonia gas s prepared byheating the mixture of ammonium chloride andcalcium hydroxide in the ratio 2:1.
2NH₄CL + Ca(OH)₂ ---------> Cacl₂ +2H₂O + 2NH₃

How do you identify ammonia gas? Write down any three methods.

We can identifyammonia gas by the following ways:
-Treating moist red litmus paper withammonia.It turns blue since ammonia is basic in nature.
-It has a strong pungent odor.
-When a glass rod dipped in conc. Hcl is broughtincontact with ammoniagas,it forms a white fumeof NH₄cl.

Write down any four physical properties of ammonia gas?

Any four physical properties of ammonia gas are:
-It is colorless, tastelessgas having strong pungent odor.
-It is lighter than air.
-It is highly soluble in water.
-It is basic in nature.
-It is non-combustible gas.

Write down three chemical properties of ammonia gas with balanced chemical eqn .

Any three chemical properties of ammonia gas are:
- Ammonia dissolves in water and forms analkali ie, ammonium hydroxide.
NH₃ + H₂O ------> NH₄OH
-Ammonia is a basic gas. So, it reacts with acidto give salt.
NH₃+ Hcl -------> NH₄CL
-Ammonia reacts with water and Forms nitrogengas and water.
4NH₃ + 3O₂ -------> 2N₂ + 6H₂O

Describe Harber's process for industrial preparation of ammonia gas.

For commercial purpose, ammonia gas is manufacturedby Harber's process. In this process, a mixture of nitrogen and hydrogen (1:3) is combined directly at500ºc temperature and 200 to600 atm. For this reactionfinely powdered iron is taken as a catalyst andmolybdenumas apromoter.
N₂ + 3H₂ -----------> 2NH₃

The hard glass test tube is slight inclined during the preparation of ammonia gas. Why?

We all know, a hard glass test tube is slightlyinclined during preparation of ammonia gas, otherwisethe steam produced during the reaction exerts pressure, which maycrack the test tube. So, the HGTT isslanted to prevent it from cracking.

Ammonia is collected in inverted gas jar. Why?

We all know, ammonia is lighter than air. So, itflows upward in the free state. Therefore, the gas jar isinverted to collect the ammoniagas by downwarddisplacementof air.

Moist red litmus paper is brought near the mouth of gas jar filled with ammonia. Why?

Moist red litmus paper is brought near the mouth ofgas jar filled with ammonia to testwhether the gasis ammonia or not. Since, ammoniagas is basicinnature, it turns moist red litmus paper to blue.

Ammonia is not collected by the downward displacement of water. Why?

Ammonia gasis not collected by downward displacementof water because it is highly soluble in water andgives ammonium hydroxide.
NH₃ + H₂O ----------> NH₄OH

How is urea prepared? Write down its balanced chemical equation.

Urea is produced when ammonia and carbon dioxidereact together at about 1500Cunder certain pressure(30atom).
2NH₃ + CO₂----------> NH₂ - CO - NH₂ + H₂O

What are the uses of ammonia gas?

The uses of ammoniagas are:
-It is used to manufacture chemical fertilizers.
-Liquidammoniais used in refrigerators.
-It is used to develop blueprint of maps.
-It is used to make medicines.
-It is used as laboratory reagent.

Which gas is prepared by heating a mixture of NH4Cl and CA(OH)2? Write balanced chemical eqn.

Ammonia gas prepared by heating a mixture ofNH₄CL and CA(OH)₂.
2NH₄Cl + Ca(OH)₂---------> CaCl₂ + 2H₂O + 2NH₃

What happens when a glass rod dipped in conc. HCl is inserted into a gas jar of ammonia? Write the balanced chemical eqn.

When a glass rod is dipped in conc. HCl is brought incontact with ammonia gas, it forms a white fumeof ammonium chloride (NH₄Cl).
HCl + NH₃ ------------>NH₄Cl

Write down the principle of the laboratory preparation of carbon dioxide gas with a balanced chemical eqn and well balanced figure.

In the laboratory, carbon dioxide gas is preparedby the reaction of dilute hydrochloric acid withcalcium carbonate (limestone or marble).
CaCO₃ + 2HCl ----------> CaCl₂ + H₂O + CO₂

Describe the different methods to test the carbon dioxide.

The different methods to test the carbon dioxide are:
-Putting the burning matchstick into the jar containing CO₂. If it extinguishes.
-When CO₂ is passed through lime water, it turnsmilky white due to the formation of insoluble CaCo₃.When CO₂ is passed in lime water for long time, themilky color disappearsdue to the formation of solubleCa(HCO₃)₂.
-CO₂ turns blue litmus paper to red because it isacidicin nature.

Write down the precautions needed during the laboratory preparation of carbon dioxide gas.

The precautions needed during the laboratorypreparation of CO₂ are:
-The apartus should be made air tight.
-The Lower end of deliverytube should not touch thesolution within the woulfe's bottle.
-The lower end of thistle funnel should be dipped inthe solution.
-Carbon dioxide is collected in the gas jar by theupward displacementof air.

Write any four physical properties of CO2 gas.

Any 4 physical properties of CO₂ gasare:
-It is colorless, odorless and tasteless gas.
-It is heavier than air.
-It is acidic in nature.
-It is neithercombustible nor a supporter ofcombustion.
-It is soluble in wader and produce carbonic acid when dissolved in water.

Write down any 3 chemical properties of carbon dioxide gas with balanced chemical eqn.

Any 3 chemical properties of carbon dioxide gas are:
-CO₂ reacts with water and gives carbonic acid.
CO₂ + H₂O ----------> H₂CO₃
-Green plants concert solar energy into chemicalenergy by photosynthesis. In this process CO₂ andwater react to give starch and oxygen.
6CO₂ + 6H₂O ----------> C₆H₁₂O₆ + 6O₂
- CO₂ reacts with lime water and gives insolublecalciumcarbonate (CaCO₃), which makes the solution milky white.
CO₂ + Ca(OH)₂ ----------> CaCO₃ + H₂O

How is CO2 manufacture on a commercial scale?

For commercial purpose, carbon dioxidegas ismanufactured by heating calcium carbonate. During thisprocess, calcium oxide i.e. lime or quick lime is alsoproduced.
CaCO₃ -------------> CaO + CO₂

When we pass CO2 in lime water, it becomes milky white. Why?

When we pass CO₂ in lime water, it becomesmilkywhite due to the formation of insoluble calcium carbonate (CaCO₃).

When carbon dioxide is passed for long time in milky white lime water, the milky color disappears. Why?

Whencarbon dioxide is passed in lime water for a long time, themilky colordisappearsslowly due to the formation of watersoluble calcium bicarbonate [Ca(HCO₃)₂].
CaCO₃ + H₂O + CO₂ --------> Ca(HCO₃)₂

Carbon dioxide is collected by upward displacement of air. Why?

Carbon dioxide gas is collected in the gas jar by the downward ofair because it is heavier than air which cause itto flow to the surface.

Carbon dioxide is found in deep wells, mines, caves, etc. Why?

We all know, carbon dioxide gas is heavier than air which causeit to flow to the lower surface. Therefore,carbon dioxide gas isfound in lower surface like deep wells, mines, caves,etc.

What is dry ice? Write down one use.

Dry ice is the solid substance formed when CO₂ gasis cooled to below -78c.
-It is used as a refrigerantto preserve foods.

What happens when CO2 is passed into line water for a while?

Lime water turns milky in color due to theformationof insoluble calcium carbonate (CaCO₃).
CO₂ + Ca(OH)₂ -------------> CaCO₃ + H₂O

What happens when a burning magnesium ribbon is inserted in the gas jar containing CO2?

The ribbon burns in CO₂gaswith dazzling light.

What happens when a balloon filled with CO2 is left free in the air?

A balloon filled with CO₂ left free in the air will fall on the surface of the land because CO₂ cause it to fall due to its higher density than that of air.

What happens when calcium bicarbonate solution is heated?

When Ca(HCO₃)₂ solution is heated, it gives calciumcarbonate, water and CO₂.
Ca(HCO₃)₂ -------------> CaCO₃ + H₂O + CO₂

What happens when a mixture of carbon dioxide and water tastes sour?

We all know, CO₂ gas is acidic in nature and wateris neutral. When a mixture of CO₂ and H₂O is madethe mixture will have acidicPH. which stimulates thetaste buds with sour taste.

What are the uses of carbon dioxide gas?

The uses of carbon dioxidegas are:
-Green plants use CO₂ during photosynthesis.
-It is used on fire extinguishers.
-It is used to manufacture fertilizers.
-It is used to make soft as well as hard drinks.
-It used in carbonation process to purifysugarcanejuice.

What do you mean by upward displacement of air?

During collection of gases in laboratory, if the freshly prepared gas settles at the bottom of the vessel or container (used to collect the gas), such that it displaces (moves) the air present in the container upwards. This is called upward displacement of air.

During preparation of Carbon Dioxide gas, as CO₂ is heavier than air, it settles at the bottom. This causes the earlier gases to move upward or displace upward.

What do you understand by downward displacement of air?

Ammonia gas can be prepared in the laboratory by heating two solid sunstances together. Write the name and molecular formula of two solid sunstances used in this process

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