What does below chemistry rebus means?

A shepherd had 18 sheep, out of which, all but ten died.

Can you tell us how many sheep was he left with?

Imagine you are in a room with no windows or doors. How will you get out?

A man dies of old age on his 25 birthday. How is this possible?

Double it and multiply it by 4. Then divide it by 8 and you’ll have it once more. What number is it?

Here is what you have to do. You have to throw a ball as hard as you can but it must return back to you even if it does not bounce at anything. Also, you have nothing attached to the ball. There is no one on the other end to catch that ball and throw it back at you.

How will you do it?

In front of you, there are 9 coins. They all look absolutely identical, but one of the coins is fake. However, you know that the fake coin is lighter than the rest, and in front of you is a balance scale. What is the least number of weightings you can use to find the counterfeit coin?

Manish and Manoj play 5 games of chess.
Both Manish and Manoj win the exact same number of games. There is no tie at all.

How?

As we know that white starts the game of chess. Can you find the scenario shown in the picture below is possible when all the white pieces are at the original place while the black pawn is not as in the below picture?

Find the number of squares in the below picture