Science: 2016: CBSE: [Delhi]: Set – III
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Q1
Select saturated hydrocarbons from the following :
C3H6 ;C5H10 ; C4H10 ; C6H14 ; C2H4
Marks:1View AnswerAnswer:
C4H10 and C6H14
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Q2
What happens when a Planaria gets cut into two pieces?
Marks:1View AnswerAnswer:
Planaria reproduces by regeneration. If a planaria gets cut into two pieces, both the parts regenerate and develop into two new planaria.
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Q3
Why are green plants called producers?
Marks:1View AnswerAnswer:
Green plants are called producers because they prepare their own food by the process of photosynthesis.
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Q4
What is meant by power of a lens? What does its sign (+ve or –ve)indicate? State its S.I. unit. How is this unit related to focal lengthof a lens?
Marks:2View AnswerAnswer:
Power of a lens is defined as the reciprocal of the focal length expressed in metres. It’s positive value indicates that the lens is convex and it’s negative value indicates that the lens is concave. SI unit of power of lens is m-1, called diopter (D). Power is related to focal length of the lens in following ways:
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Q5
List four advantages of properly managed watershed management.
Marks:2View AnswerAnswer:
The four advantages of properly managed watershed management are:
i. It helps to maintain equal and sustainable distribution of water.
ii. It enhances the level of groundwater.
iii. It maintains the quality of water.
iv. It provides protection from floods by controlling the flow of rainwater. -
Q6
“Reuse is better than recycling of materials”. Give reason to justify this statement.
Marks:2View AnswerAnswer:
Reuse is better than recycling as reusing saves money, energy and labour. It also creates less air, water and land pollution as compared to recycling.
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Q7
Name the compound formed when ethanol is heated in excess ofconc. sulphuric acid at 443 K. Also write the chemical equation ofthe reaction stating the role of conc. sulphuric acid in it. What
would happen if hydrogen is added to the product of this reactionin the presence of catalysts such as palladium or nickel?
Marks:3View AnswerAnswer:
Ethene is formed when ethanol is heated in excess of conc. sulphuric acid at 443 K.
In this reaction Conc. H2SO4 acts as a dehydrating agent and removes the water from the reactant.
If hydrogen is added to the product of this reaction in the presence of catalysts such as palladium or nickel Ethane (C2H6) will be formed.
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Q8
When ethanol reacts with ethanoic acid in the presence of conc. H2SO4, a substance with fruity smell is produced. Answer the following:
(i) State the class of compounds to which the fruity smelling compounds belong. Write the chemical equation for the reaction and write the name of the product formed.
(ii) State the role of conc. H2SO4in this reaction.
Marks:3View AnswerAnswer:
(i) The fruity smelling compound belongs to the class of esters.
The name of product is Ethyl ethanoate.
(ii) In this reaction, conc. H2SO4 acts as a dehydrating agent and helps in the removal of water formed in the reaction.
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Q9
Two elements ‘A’ and ‘B’ belong to the 3rd period of Modernperiodic table and are in group 2 and 13 respectively. Comparetheir following characteristics in tabular form :
(a) Number of electrons in their atoms
(b) Size of their atoms
(c) Their tendencies to lose electrons
(d) The formula of their oxides
(e) Their metallic character
(f) The formula of their chlorides
Marks:3View AnswerAnswer:
S.No.
Characteristics
Element A
Element B
(a)
Number of electrons in their atoms
12
13
(b)
Size of their atoms
Bigger
Smaller
(c)
Their tendencies to lose electrons
More
Less
(d)
The formula of their oxides
AO
B2O3
(e)
Their metallic character
More
Less
(f)
The formula of their chlorides
ACl2
BCl3
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Q10
An element ‘M’ with electronic configuration (2,8,2) combines separately with (NO3)–, (SO4)2– and (PO4)3– radicals. Write the formula of the three compounds so formed. To which group and period of the Modern Periodic Table does the elements ‘M’ belong? Will ‘M’ from covalent or ionic compounds? Give reason to justify your answer.
Marks:3View AnswerAnswer:
The electronic configuration (2, 8, 2) of the element ‘M’ suggests that itbelongs to group 2 (presence of 2 electrons in valence shell) and period 3 (presence of 3 shells) of the Modern Periodic Table and its valency is 2.
The chemical formulas of three compounds are –
M (NO3)2 , MSO4 , M3 (PO4)2respectively.
‘M’ will form ionic compounds by losing two electrons present in the valence shell.
