English Medium इयत्ता १० - CBSE Question Bank Solutions

The table shows the electronic structures of four elements. 

1.  Identify which element(s) will form covalent bonds with carbon.
2. “Carbon reacts with an element in the above table to form several compounds.” Give suitable reason.

DDT was sprayed in a lake to regulate breeding of mosquitoes. How would it affect the trophic levels in the following food chain associated with a lake? Justify your answer.

In the following food chain, vertical arrows indicate the energy lost to the environment and horizontal arrows indicate energy transferred to the next trophic level. Which one of the three vertical arrows (A, C and E) and which one of the two horizontal arrows (B and D) will represent more energy transfer? Give reason for your answer.

A food chain in a forest ecosystem

Which of the following is the correct observation of the reaction shown in the above set up?

These consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below:

Assertion: On freely suspending a current – carrying solenoid, it comes to rest in Geographical N-S direction.

Reason: One end of current carrying straight solenoid behaves as a North pole and the other end as a South pole, just like a bar magnet.

A compass needle is placed near a current carrying wire. State your observations for the following cases and give reasons for the same in each case -

1. Magnitude of electric current in wire is increased.
2. The compass needle is displaced away from the wire.

"Carbon prefers to share its valence electrons with other atoms of carbon or with atoms of other elements rather than gaining or losing the valence electrons in order to attain noble gas configuration." Give reasons to justify this statement.

When is the force experienced by a current-carrying straight conductor placed in a uniform magnetic field.

1. Maximum
2. Minimum

In the following food chain, only 2J of energy was available to the peacocks. How much energy would have been present in Grass? Justify your answer.

GRASS → GRASS HOPPER → FROG → SNAKE → PEACOCK

State the reasons, why carbon cannot

1. Lose four electrons to form C⁴⁺ cation and
2. Gain four electrons to form C^4- anion.

How does carbon overcome this problem to form compounds?

Assertion (A): The energy which passes to the herbivores does not come back to autotrophs.

Reason (R): The flow of energy in a food chain is unidirectional.

Assertion (A): Melting point and boiling point of ethanol are lower than that of sodium chloride.

Reason (R): The forces of attraction between the molecules of ionic compounds are very strong.

To balance the following chemical equation the value of x and y should respectively be:

\[\ce{2NaOH + xAl_2O_3->yNaAlO_2 + H_2O}\]

If a harmful chemical enters a food chain comprising peacocks, plants, rats and snakes, which of these organisms is likely to have the highest concentration of the chemical in its body? Justify your answer. Name the process involved and define it.

When aqueous solutions of potassium iodide and lead nitrate are mixed an insoluble substance separates out. The chemical equation for the reaction involved is: 

The electron dot structure of chlorine molecule is:

Two LED bulbs of 12W and 6W are connected in series. If the current through 12W bulb is 0.06A the current through 6W bulb will be ______.

A student took a small amount of copper oxide in a conical flask and added dilute hydrochloric acid to it with constant stirring. He observed a change in colour of the solution. 

1. Write the name of the compound formed and its colour.
2. Write a balanced chemical equation for the reaction involved.

Use of several pesticides which results in excessive accumulation of pesticides in rivers of ponds, is a matter of deep concern. Justify this statement. 

It is observed that covalent compounds are had conductors of electricity. Give reason.