What does below chemistry rebus means?

Which is the smallest number that you can write using all the vowels exactly once?

Can you convert the number zero(0) into a positive number using just one mathematical operator ?

On the dull night when the blonde was dozing, she heard an odd clamour and she saw that there was a bizarre man with a gun simply outside her home. So she raced to the telephone to call the police, however, she can't dial 911. Why?

A Doctor always sneezes before the rain. Doctor sneezes, Will it rain?

There are forty elephants and they have forty-fore heads. How can this be possible?

I am 5 letters long.
My first two tell you who I am
My first 3 could be a medicine
My last three reversed could be a young boy.
My 4th, 3rd and 2nd in that order could be a fruit drink.
If you have me you may hang me round your neck
WHAT AM I ?

I am not alive, but I grow; I don't have lungs, but I need air; I don't have a mouth, but water kills me. What am I?

What does this rebus means ?

PROG WORKRESS

A horse was tied to a rope 5 meters long and the horses food was 15 meters away from the horse. How did the horse reach the food?