Science: 2017: CBSE: [Delhi]: Set – III

The molecular formula of first member is CH₃OH and the molecular formula of second member is C₂H₅ OH.

Plasmodium reproduces asexually through the process of multiple-fission. In this method, repeated division of the parent nucleus is followed by division into many daughter cells.

A lake ecosystem is a natural ecosystem consisting of biotic components - all plants, animals and micro-organismsin that area functioning together with abiotic components - all of the non-living physical factors of the environment.

Focal length = radius of curvature/2

= 30 cm/2 = 15 cm

Thus, the object is placed between the pole and the focus of the concave mirror. The ray diagram in this case is as shown below:

Four characteristics of the image formed by the mirror are:

(i) The image is formed behind the mirror.

(ii) The image formed is virtual.

(iii) The image formed is erect.

(iv) The image formed is enlarged.

Natural resources are limited in nature so we must aim at adopting steps in daily life for conservation of natural resources. For long term perspective we must aim at judicious use of natural resources as they are limited in nature and we should conserve them for future generation. We should use natural resources in judicious and ecofriendly manner to ensure equal distribution among the people.

Wildlife is defined as the biota including both, animals and plants that grow independentlyof people, usually in the natural ​conditions. It includes all the non-domesticated and non-cultivated flora and fauna of a geographic region.

Wildlife is important as it plays an essential role in the functioning of the food webs and the food chains and thus maintaining the ecological balance of an ecosystem. Not just this, it is also important for the maintenance of aesthetic, educational, historical and scientific values, for maintaining the genetic diversity.All crops and domestic animals have descended from their wild varieties and many wildlife species yield products of immense medicinal value.

The general formula of alkenes is C_nH_2n. Therefore, the molecular formula C₄H₈ represents an alkene

The general formula of alkanes is C_nH_2n+2. Therefore, the molecular formula C₃H₈ represents an alkane.

Alkane is a saturated hydrocarbon whereas alkene is an unsaturated hydrocarbon. Since, addition reactions are characteristic of alkenes. Therefore, C₄H₈   is likely to show addition reactions. The reaction in which an unsaturated hydrocarbon combines with another substance to give a single product is called an addition reaction. It is a characteristic property of unsaturated hydrocarbons (alkenes and alkynes).

The unsaturated compounds have multiple bonds. During the addition reactions, the addition takes place at multiple bond and new single bonds are formed.

Modern Periodic Table has 18 vertical columns known as ‘Group’ and 7 horizontal rows are known as ‘Period’.

(a) On moving down in a vertical column metallic character increases because on moving down in a group atomic size increases due to addition of a new shell, therefore, it can easily lose electrons from its valence shell.

(b) On moving left to right in a horizontal row atomic size decreases because nuclear charge on valence shell electrons increases.

(i) Positions in Periodic Table:

Electronic configuration of element with atomic number 20 is 2, 8, 8, 2. According to its configuration, P belongs to 2^nd group because it has 2 electrons in its outermost shell and 4^th period of the modern periodic table as the element is of N electronic shell.

On the other hand, electronic configuration of element ‘Q’ with atomic number 17 is 2, 8, 7. According to its configuration, Q belongs to 17^th group because it has 7 electrons in its outermost shell and 3^rd period of the modern periodic table as the element is of M electronic shell.

(ii) Molecular formula of compound formed:

Atomic number of P = 20
Electronic configuration of P = 2,8,8,2
Number of valence electrons of P = 2
Valency of P = 2

Atomic number of Q= 17
Electronic configuration of Q = 2,8,7
Number of valence electrons of Q = 7
Valency of Q = 8 - 7 = 1
Therefore the formula of the compound formed is PQ₂.