Daily NEET MCQ- May 5, 2022 - NEET MCQ

In the case of liquids when temperature increases, viscosity decreases because it is the result of molecular bonds (electromagnetic forces) between particles which weaken due to random motion brought about by increase in temperature. In the case of gases, the molecules vibrate more randomly, leading to more obstruction in the path of bodies trying to move through it. And we interpret this increased obstruction as increased viscosity of the gas.

We know that the shear strain rate is v/l, where v is velocity of layer and l is distance of that layer from layer having zero speed Here, the layer in contact with pipe wall will have zero speed. Therefore, the velocity will increase as one goes away from the wall and will be maximum at centre.

The group valance can be calculated from Lewis symbols either by subtracting it from eight (more than 4) or having it equal (less than 4). The halogen family has 7 electrons in their outer orbit. So 8 – 7 = 1. Therefore the valency of the halogen family is 1.

According to Kossel, Highly electropositive Alkali metals are separated from highly electronegative halogens by noble gases. This is because Alkali metals are the 1st group and halogens the 17th group. Elements in 18th group i.e. nobles are preceded by group 17 elements and succeeded by group 1 elements.

As per the electronic theory of chemical bond that’s put forth by Lewis &Kossel states that the atoms follow the octet rule by sharing or transfer of electrons from one atom to the other to attain stable octet configuration.

The mode of classifying plants as shrubs, herbs and trees come under artificial classification. In this mode of classification, morphological characteristics of plants are considered to be the basis of classification.

Natural classification overcomes the limitations of the plants. Both internal and external structures are considered to be the basis of natural classification. Natural classification considers reproductive mode, embryotic structure and ultra structure of plants. It establishes close relationship between plants.

Phylogenetic classification considers evolutionary relationships between organisms. Fossil records, cytotaxonomy, chemotaxonomy and numerical taxonomy help in studying their evolutionary structures.

Numerical classification is based on mathematical calculations based on observable characteristics. In this mode of classification, each character is given a number or a code. The more the number of similar characters, the more is the chance that they belong to similar taxon. The main disadvantage of numerical taxonomy comes with the variation in result with variation in set of characteristics.

Cytotaxonomy is based on the chromosomes present in the organism. Cytotaxonomy involves both internal and external characteristics of plant. Cytotaxonomy involves characteristics like number of chromosomes, division of cell and position centromere. Chemotaxonomy is based on the chemical composition of plants.