English Medium Class 10 - CBSE Question Bank Solutions for Science

The electronic configurations of three elements X, Y and Z are as follows:

(a) Which two elements will combine to form an ionic compound?
(b) Which two elements will react to form a covalent compound?
Give reasons for your choice.

Which of the following cannot exhibit isomerism?
(a) C₄H₁₀
(b) C₅H₁₂
(c) C₃H₈
(d) C₆H₁₄

The pencil leads are made of mainly:
(a) lithium
(b) charcoal
(c) lead
(d) graphite

The number of isomers formed by the hydrocarbon with molecular formula C₅H₁₂ is:
(a) 2
(b) 5
(c) 3
(d) 4

An element A has 4 valence electrons in its atom whereas element B has only one valence electron in its atom. The compound formed by A and B does not conduct electricity. What is the nature of chemical bond in the compound formed? Give its electron-dot structure.

The number of carbon atoms joined in a spherical molecule of buckminsterfullerene is:
(a) fifty
(b) sixty
(c) seventy
(d) ninety

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:

(a) What type of chemical bond is formed between the two atoms of A?
(b) 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 substance 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. In 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.

Write the balanced equation for the following chemical reaction.

\[\ce{Barium chloride + Aluminium sulphate -> Barium sulphate + Aluminium chloride}\]

Your mother always thought that fruit juices are very healthy for everyone. One day she read in the newspaper that some brands of fruit juices in the market have been found to contain certain level of pesticides in them. She got worried as pesticides are injurious to our health.
(a) How would you explain to your mother about fruit juices getting contaminated with pesticides?
(b) It is said that when these harmful pesticides enter our body as well as in the bodies of other organisms they get accumulated and beyond a limit cause harm and damage to our organs. Name the phenomenon and write about it.

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

"Energy flow in food chains is always unidirectional". Justify this statement. Explain how the pesticides enter a food chain and subsequently get into our body.

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.

Dry raisins were soaked in water for 2 hours, to determine the percentage of water absorbed by raisins. Before final weighing of swollen raisins, the extra water left on the surface of soaked raisins was removed by:

While performing the experiment with raisins to determine the percentage of water absorbed by them, a student made following measurements:

Mass of water in the beaker = 40 g

Mass of raisins before soaking = 5 g

Mass of raisins after soaking for 2 hours = 8 g

Mass of water left in the beaker after the experiment = 35 g

The percentage of water absorbed by raisins is: