What does below chemistry rebus means?

In an Art Gallary, When the clock hit 11 am, Artist hung the painting number 30. When it struck 4 pm, he hung painting number 240 and when it struck 7:30 pm, he hung painting number 315.

Can you determine, which painting number will he hang when the time is 9:20 pm?

What has a bottom at the top?

A man is approaching a broad and barren land. He has a package with him. If somehow, he is unable to open the package before reaching the land, he will die.

Can you guess what is present in the package?

Make eight squares by moving only two matchsticks.
Note- Square can be of different sizes.

I have a five and a three-gallon jar. Assuming there is an infinite supply of water, how can I measure one-gallon water?

You find yourself in a strange place guarded by two guards.One of the guard always say truth while other always lies.You don't know the identity of the two.You can ask only one question to go out from there. What should you ask?

All of the flowers I have are orchids except two. All of the flowers I have are hibiscuses except two. All of the flowers I have are roses except two.

Can you tell me how many flowers I have?

I am sometimes honest
Sometimes dishonest
I can be sweet and also bitter
I can hurt you real bad and
also make u smile and blush ☺️
What am I?

Baseball bat and ball cost $100. If the bat cost $99 more than the ball, what is the cost of each?