I really suck at chemistry so please help me out

2Al2O3 --> 4Al + 3O2

Explanation:

Ok so balancing equations means that there is an equal amount of atoms on both sides.

So let's list how much there is on each side

Reactants:

Al-2

O-3

Products:

Al-1

O-2

First of all, oxygen has 2 on the products side but 3 on the reactants side. If you add a 2 to Al2O3 and a 3 to O2, they will have the same amount.

Al-4

O-6

Al-1

O-6

Ok now we need the Al to be balanced. This can be done by putting a 4 in front of Al.

Al-4

O-6

Al-4

O-6

It looks like a lot of work but over time you should be able to just look at it and know what's missing!!

why do the isotopes of a particular element behave differently in nuclear reactions but the same in chemical reactions? chemical reactions involve changes to electrons in an atom; isotopes do not differ in electrons, and so they react the same way during chemical changes.

c is the answer because when something is left after something evaporates that shows the chemical change.