Periodic Classification of Elements — Science STD 10 — Question

Explain the formation of a chlorine molecule on the basis of electronic theory of valency.

State the meaning of the functional group in an organic compound. Write the formula of the functional group present in alcohols, aldehydes, ketones and carboxylic acids.

A colourless lead salt, when heated, produces a yellow residue and brown fumes:

1. Name the lead salt.
2. Name the brown fumes.
3. Write a chemical equation of the reaction involved.

The human brain can be broadly divided into three regions. Name these three regions.

Find the position and nature of the image of an object 5cm high and 10cm in front of a convex lens of focal length 6cm.

A coil is connected to a galvanometer. When the N-pole of magnet is pushed into the coil, the galvanometer deflected to the right. What deflection, if any, is observed when:

1. The N-pole is removed?
2. The S-pole is inserted?
3. The magnet is a rest in the coil?

Leaves of a healthy potted plant were coated with vaseline. Will this plant remain healthy for long? Give reason for your answer.

F, CI and Br are the elements each having seven valence electrons. Which of these,

1. Has the largest atomic radius.
2. Is most reactive? Justify your answer stating reason for each.

The magnification of an image formed by a lens is -1. If the distance of the image from the optical centre of the lens is 25 cm, where is the object placed? Find the nature and focal length of the lens. If the object is displaced 15 cm towards the optical centre of the lens, where would the image be formed? Draw a ray diagram to justify your answer.

Explain why, a solution of cane sugar does not conduct electricity but a solution of common salt is a good conductor of electricity.