 Next, we'll look at acids reacting with metals. Not all metals react with acids, but of those that do, this is the way they do it. Let's look at nitric acid reacting with iron. So one product we know, it's hydrogen gas. Where does that come from? Well it must be the protons from the acid, there are no other hydrogen atoms here. So they become the hydrogen gas. So then the salt must be formed from the metal and from the anion left over from the acid, so that would give us iron nitrate. And then we can balance the reaction. How about another? Sulfuric acid reacting with magnesium. One product is hydrogen, and the other will be made from the metal and the acid and iron. So magnesium sulfate. Now here's an interesting one. You know that when you put sodium metal into water it reacts, unlike many other metals. This turns out to be a very similar reaction, and this is what happens. Water and sodium give sodium hydroxide and hydrogen. Can you see the link? Here water is acting as an acid. It is donating protons to form the hydrogen gas, and then the remaining anion from the acid is hydroxide. So the salt that is formed is sodium hydroxide.