Life Processes — Science STD 10 — Question

Carbon forms four covalent bonds by sharing its four valence electrons with four univalent atoms, e.g. hydrogen. After the formation of four bonds, carbon attains the electronic configuration of:

Which of the following metals are extracted by the electrolysis of their molten chlorides?

In cockroaches, air enters the body through:

Which of the following carries substances upwards as well as downwards in a plant?

Out of aluminium, copper, calcium and tin, the most reactive metal is:

An aqueous solution 'A' turns the phenolphthalein solution pink. On addition of an aqueous solution 'B' to 'A', the pink colour disappears. Which of the following statement is true for the solutions 'A' and 'B'.

The electrical resistance of insulators is :

If copper is kept open in air, it slowly loses its shining brown surface and gains a green coating. It is due to the formation of :

The growth of a pollen tube towards the ovule caused by a sugary substance as stimulus is an example of:

A student has obtained a magnified image of a flame on a screen using a convex lens. To draw the corresponding ray diagram, to show the image formation, which of the following two rays whose paths after refraction are shown he should select?