English Medium Class 10 - CBSE Question Bank Solutions

A solid element X has four electrons in the outermost shell of its atom. An allotrope Y of this element is used as a dry lubricant in machinery and also in making pencil leads.

(a) What is element X?

(b) Name the allotrope Y.

(c) State whether allotrope Y is a good conductor or non-conductor of electricity.

(d) Name one use of allotrope Y (other than lubrication and pencil leads)

(e) Name two other allotropes of element X.

The electronic configurations of two elements A and B are given below:

1. What type of chemical bond is formed between the two atoms of A?
2. What type of chemical bond will be formed between the atoms of A and B?

You can buy solid air-freshners in shops. Do you think these substances are ionic or covalent? Why?

Give the formulae of the chlorides of the elements X and Y having atomic numbers of 3 and 6 respectively. Will the properties of the two chlorides be similar or different? Explain your answer.

An element E exists in three allotropic forms A, B and C. In allotrope A, the atoms of element E are joined to form spherical molecules. In allotrope B, each atom of element E is surrounded by three other E atoms to form a sheet like structure. În allotrope C, each atom of element E is surrounded by four other E atoms to form a rigid structure.
(a) Name the element E.
(b) What is allotrope A.
(c) What is allotrope B?
(d) What is allotrope C?
(e) Which allotrope is used in making jewellery?
(f) Which allotrope is used in making anode of a dry cell?

What happens when methane (natural gas) burns in air? Write the chemical equation of the reaction involved.

Which element exhibits the property of catenation to maximum extent and why?

Elements forming ionic compounds attain noble gas electronic configuration by either gaining or losing electrons from their valence shells. Explain giving reason why carbon cannot attain such a configuration in this manner to form its compounds. Name the type of bonds formed in ionic compounds and in the compounds formed by carbon. Also explain the reason why carbon compounds are generally poor conductors of electricity.

Distinguish between ionic and covalent compounds under the following properties:

(i) Strength of forces between constituent elements

(ii) Solubility of compounds in water

(iii) Electrical conduction in substances

Answer the following question.
What is methane? Draw its electron dot structure. Name the type of bonds formed in this compound. Why are such compounds:
(i) poor conductors of electricity? and  
(ii) have low melting and boiling points? What happens when this compound burns in oxygen?

The chemical formula for plaster of Paris is:

List two differences between the properties exhibited by covalent compounds and ionic compounds.

At what temperature is gypsum heated to form Plaster of Paris?

How many water molecules does hydrated calcium sulphate contain?

Which of the following is the purest form of carbon?

When ethyl alcohol and acetic acid are mixed, the resulting ester has a chemical formula ______.

The correct structural formula of butanoic acid is -

Acetic acid was added to a solid X kept in a test tube. A colourless, odourless gas Y was evolved. The gas was passed through lime water, which turned milky. It was concluded that ______.

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 ______.