Read the extract given below and answer the questions that follow:

How they toiled and sweated to get the hay in! But their efforts were rewarded, for the harvest was an even bigger success than they...

1. What are free electrons?
2. Why do they not leave the metal surface on their own?
3. How can they be made to leave the metal surface?

Identify the substance underlined in each of the following:

1. The electrode that increases in mass during the electro-refining of silver.
2. The acid that is a dehydrating as well as a drying agent.
3. The
...

F, B, N, O (In the increasing order of electron affinity)

Write a balanced chemical equation: Action of dilute sulphuric acid on zinc sulphide

1. Name the waves used for echo depth sounding.
2. Give one reason for their use for the above purpose.
3. Why are the waves mentioned by you not audible to us?

Two pendulums C and D are suspended from a wire as shown in the figure given below. Pendulum C is made to oscillate by displacing it from its mean position. It is seen that D also starts...

Displacement distance graph of two sound waves A and B, travelling in a medium, are as shown in the diagram below.

Study the two sound waves and compare their:

1. Amplitudes
2. Wavelengths

Action of dilute Hydrochloric acid on iron (II) sulphide.

An element with the atomic number 19 will most likely combine chemically with the element whose atomic number is:

1. 17
2. 11
3. 18
4. 20

The necessity to maintain International peace led to the establishment of the United Nations Organisation. With reference to the statement, answer the following: Write any four functions of the...

Heating of Ethanol at 170oC in the presence of conc. Sulphuric acid.

Write a balanced chemical equation.

Higher the pH value of a solution, the more __________ (acidic / alkaline) it is.

Reaction of Ammonia with heated copper oxide.

Action of heat on aluminum hydroxide.

Find the value of k for which the following equation has equal roots.

$x^2 + 4kx + (k^2 - k + 2) = 0$