CBSE 12th Standard Chemistry Subject The p-Block Elements Value Based Questions 3 Mark Questions With Solution 2021
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CBSE 12th Standard Chemistry Subject The p-Block Elements Value Based Questions 3 Mark Questions With Solution 2021
12th Standard CBSE
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Reg.No. :
Chemistry
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It is desired to produce ammonia gas from nitrogen and hydrogen according to the reaction:
\({ N }_{ 2 }(g)+3H_{ 2 }(g)\rightleftharpoons 2NH_{ 3 }(g)+Heat\)
Above reaction is exothermic and therefore, favored by low temperature. As a student of chemistry,which temperature would you suggest 350k or 750 k? Justify -
Nitrogen fertilizers are commonly used to promote the growth of plants and boost the crop yield.As a student of chemistry,can you suggest a farmer whether he should use excess nitrogen fertilizers to get maximum yield or not?
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Sulphuric acid is manufactured by Contact process.During the process,the following reaction takes place:
\({ 2SO }_{ 2 }(g)+O_{ 2 }(g)\rightleftharpoons 2SO_{ 3 }(g)\)
This reaction is favoured by high pressure, However,the pressure is not increase beyond 3 bar.As a students of chemistry how will you justify this? -
Account for the following:
(i) Iron on reaction with HCI forms FeCl2 and not FeCI3.
(ii) Draw structure of XeO3.
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CBSE 12th Standard Chemistry Subject The p-Block Elements Value Based Questions 3 Mark Questions With Solution 2021 Answer Keys
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The reaction is exothermic and therefore, according to Le Chatelier's principle, it should be favoured by low temperature. However, the reaction should be carried out at an optimum temperature of about 750 K and not at 350 K. This is because the collision frequency of the reactant molecules decreases with decrease in temperature. As a result, the rate of reaction would decrease at a lower temperature. Consequently, at low temperature, the yield of the product will be less. Hence, the reaction should be carried out at about 750 K.
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Nitrogen fertilisers are very useful for the growth of plants because these provide essential plant nutrients to the soil. However, these should not be used in excessive quantities. The excessive use of fertilisers has many disadvantages also. Some of these are:
(i) The excessive use of nitrogenous fertilisers concentrates nitrates in the soil and water. Nitrate rich water is unfit for drinking. When this water is carried off into surface water bodies such as rivers, lakes and ponds, it proliferates the growth of algae. These algae consume dissolved oxygen from water and therefore, decrease the oxygen content in water leading to the death of useful aquatic life such as fish. Such an increase in growth of algae in rivers, lakes, ponds etc. resulting in the reduction of oxygen content in water is called eutrophication. Eutrophication destroys the life-supporting environment in rivers, lakes and ponds.
(ii) Excessive use of fertilisers over a long period may affect the alkalinity or acidity of the soil and may adversely affect the crop production. Thus, as a student of chemistry, we should suggest the farmer use only required quantities of nitrogen fertilisers. -
Since the volume of the gaseous products is less than that of the gaseous reactants, high pressure should favour the oxidation of sulphur dioxide. But a very high pressure may cause the corrosion of the vessel in which oxidation is carried. Therefore, a pressure of 2 to 3 bar is sufficient for the oxidation.
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(i) Liberation of hydrogen prevents the formation of FeCI3.
(ii) Structure of XeO3
