Science 2016 CBSE [All India] Set-II
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Q1
Write the name and structure of an alcohol with four carbon atoms in its molecule.
Marks:1View AnswerAnswer:
The name of the alcohol with four carbon atoms in its molecule is butanol (C4H9OH).
The structure of butanol or butanol-1 is as follows:
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Q2
What are those organisms called which bear both the sex organs in the same individual. Give one example of such organism.
Marks:1View AnswerAnswer:
Organisms bearing both the sex organs in the same individual are called hermaphrodite or bisexual. Example: Hibiscus.
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Q3
Write one negative effect, on the environment, of affluent life style of few persons of a society.
Marks:1View AnswerAnswer:
Affluent life style of few persons of today’s society has increased the demand of material goods used by them. To fulfill this demand, over exploitation of natural resources is occurring, leading to more pollution.
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Q4
“The magnification produced by a spherical mirror is -3”. List four informations you obtain from this statement about the mirror/image.
Marks:2View AnswerAnswer:
The following information is obtained from the statement:
(a) Image is real
(b) Image is inverted
(c) Image is 3 times magnifies or enlarged as compared to the object.
(d) The mirror used is a Concave mirror.
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Q5
Forest are “biodiversity hot spots”. Justify this statement.
Marks:2View AnswerAnswer:
Biodiversity hot spots are the areas where the large numbers of different types of species are present. In forests, different species of plants, animals and microorganisms are present. That is why, forests are called “biodiversity hot spots”.
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Q6
What is water harvesting? How can this technique help in the conservation of water?
Marks:2View AnswerAnswer:
Water harvesting is the collection of rain water or any run off water to conserve water. This technique helps in the conservation of water in the following ways:
(1) By recharging the ground water.
(2) Ground water does not evaporate and spreads out to recharge wells.
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Q7
On dropping a small piece of sodium in a test tube containing carbon compound ‘X’ with molecular formula C2H6O, a brisk effervescence is observed and a gas ‘Y’ is produced. On bringing a burning splinter at the mouth of the test tube the gas evolved burns with a pop sound. Identify ‘X’ and ‘Y’. Also write the chemical equation for the reaction. Write the name and structure of the product formed, when you heat ‘X’ with excess conc. sulphuric acid.
Marks:3View AnswerAnswer:
The evolved gas (Y) is hydrogen because it burns with a pop sound.The compound having molecular formula C2H6O is ethanol (C2H5OH. When it reacts with sodium, hydrogen and sodium ethoxide are formed.
Hence, X= Ethanol
Y = Hydrogen
When ethanol (X)is heated with the excess of conc. H2SO4, dehydration of ethanol takes place leading to the formation of ethene.
Thus, ethene (H2C=CH2) and water (H2O) are obtained on heating ethanol with excess conc. sulphuric acid.
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Q8
An aldehyde as well as a ketone can be represented by the same molecular formula, say C3H6O. Write their structures and name them. State the relation between the two in the language of science.
Marks:3View AnswerAnswer:
As both the aldehyde and the ketone can be represented by the same molecular formula, C3H6O, the aldehyde is propanal and the ketone is propanone.
The organic compounds, having the same molecular formula but different fuctional groups are known as fuctional isomers.
Hence, both propanal and propanone are called functional isomers. They have different physical properties due to different functional groups. Propanal has aldehyde group (-CHO) while paropanone contains ketone group, , where R and R’ are alkyl groups.
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Q9
An element ‘X’ belongs to 3rd period and group 16 of the Modern Periodic Table.
(a) Determine the number of valence electrons and the valency of ‘X’.
(b) Molecular formula of the compound when ‘X’ reacts with hydrogen and write its electron dot structure.
(c) Name the element ‘X’ and state whether it is metallic or non-metallic.
Marks:3View AnswerAnswer:
(a) As the element ‘X’ belongs to 3rd period and group 16, its electronic configuration will be 2,8,6. The number of valence electrons in the element ‘X’ is 6. It gains two electrons to complete its octet. Therefore, the valency of the element ‘X’ is 2.
(b)
Molecular formula of the compound when sulphur reacts with hydrogen is H2S (Hydrogen sulphide).
Electron dot structure of H2S is as follows:
(c) The element ‘X’ is sulphur and it is non-metallic.
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Q10
Three elements ‘X’, ‘Y’ and ‘Z’ have atomic numbers 7, 8 and 9 respectively.
(a) State their positions (Group number and period number both) in the Modern Periodic Table.
(b) Arrange these elements in the decreasing order of their atomic radii.
(c) Write the formula of the compound formed when ‘X’ combines with ‘Z’.
Marks:3View AnswerAnswer:
(a)
Element
Atomic number
Group number
Period number
X
7
15
2
Y
8
16
2
Z
9
17
2
(b) On moving left to right in a period, the atomic radius decreases.The decreasing order of the atomic radii of X, Y and Z are as under:
X>Y>Z
(c) Electronic configuration of X (At.No.7) = 2,5
Electronic configuration of Z (At.No.9) = 2,7
The formula of the compound formed when ‘X’ combines with ‘Z’ is XZ3. It will be a covalent compound.
