English Medium कक्षा १० - CBSE Question Bank Solutions for Science

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. 

Carbon can neither form C^4- cation nor C⁴ anion. Why?

Name the following:

\[\ce{CH3 - CH2CH = CH2}\]

Show the covalent bond formation in nitrogen molecule.

• Assertion: A compass needle is placed near a current-carrying wire. The deflection of the compass needle decreases when the magnitude of the current in the wire is increased.
• Reason: The strength of a magnetic field at a point near the conductor increases by increasing the current.

Dil. HCl is added to Zn granules. How will you prove that chemical change has taken place here? Support your response with two arguments.

The number of single and double bonds present in a molecule of benzene (C₆H₆) respectively, are ______.

Study the picture given below showing three food chains (a), (b) and (c) and answer the following questions:

1. Name the type of ecosystems that exist in food chains (b) and (c).
2. The first trophic level in all food chains is producers. Why? What percentage of solar energy do these producers capture for their use?
3. Why are the arrows shown in the diagram in one direction only and not vice versa? Justify.