What does below chemistry rebus means?

Luis Garavito killed Density x Volume.

Who is Luis Garavito ?

If you remove one from eleven, it becomes ten. If you remove one from nine, it becomes ten.

How is this possible?

A Detective reviewed the information they had on the case so far.

A lady named 'Caterina' was found shot and they already had a list of suspects - Ankit, Tarun, Harish, Manoj and Manish.
The killer is a fan of challenges him by leaving notes ad various places.
* The first was found in a toilet room.
* The second was found in an art room.
* The third was in a restroom.
* the fourth in an underwater room.
* The fifth at the no-smoking room.

All of the notes read the same thing, 'The clues are where you find the notes.' Yet, nothing was found at any place the notes were.
Detective the genius, immediately solved the case.
Who was the killer?

Count the number of triangles in the given picture.

You can hear me, but you can't touch or see me.

What am I?

In one of the popular batman series movie "Batman Forever", there was a riddle that goes like "Tear me off and then scratch my head and I was red then and now I am back. Who am I?

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

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

I have branches, but no fruit, trunk or leaves. What am I?

Can you find the missing letter in the sequence?
S - T - I - L - ? - T - F - Y - C