Which is the most reasonable explanation for a drop of temperature for gas

Astudent reacts 13 moles of iron with 21 moles of oxygen according to the following equation:

You have a liquid that exhibits diltancy. you want to pour it from a bottle. what should you do to the bottle before pouring

How many moles of lead are in 1.50 x 10^12 atoms of lead? could you explain the answer as well and not just give it to me i am refreshing for finals and i need to know how to do it