What does below chemistry rebus means?

How many sides does a circle have?

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

Can you find the thief by just looking at the picture below?

I am not a bull but I have horns.
I am not an ass but I have a pack saddle.
Wherever I go, I leave silver behind me.

Who am I?

In two decks of cards, what is the least amount of cards you must take to be *guaranteed* at least one four-of-a-kind?

Using mathematical symbols like +, -, and x in order to make the equations correct. Replace # with the above-given symbols.

9 # 8 # 7 # 6 # 5 # 4 = 91

By moving exactly three matchsticks can you make the below equation true.It can be solved by 3 ways.

What kind of band never plays music?

I went to the bookshop and spent one-half of the money that was in my purse.

When I came out, I found that I had as many cents as I had dollars and half as many dollars as I had cents when I went in. Find the money in my purse when I entered the store.