What does below chemistry rebus means?

What's the best place to go shopping in the ocean?

What number comes next in the series?

5 15 5 18 5 24 14 20 _

What is so fragile that saying its name breaks it?

Find the hidden tiger in the given optical illusion ?

The person who makes it has no need for it; the person who buys it has no use for it. The person who uses it can neither see nor feel it. What is it?

Can you replace the question mark with the correct number in the below table sequence?

People put me on the table and cut me but do not eat me. What am I?

The host of a game show, offers the guest a choice of three doors. Behind one is a expensive car, but behind the other two are goats.
After you have chosen one door, he reveals one of the other two doors behind which is a goat (he wouldn't reveal a car).

Now he gives you the chance to switch to the other unrevealed door or stay at your initial choice. You will then get what is behind that door.

You cannot hear the goats from behind the doors, or in any way know which door has the prize.

Should you stay, or switch, or doesn't it matter?

Can you solve this tricky maths equation problem by replacing it? mark with the correct symbol?

19834 -----: 187
15921 -----: 153
17561 -----: 139
13734 -----: ???