This is going to be difficult, these sorts of reactions aren't simple ones for beginning chemistry students. However, if you're going to take a stab at them, you're going to have to start out writing the reagents as chemical formulas. You'll have to use the descriptions you're given -- when nitrate is reduced to nitrite, what happens? And what else happens, when something is reduced. Understanding the color change can be difficult, but something was changed, from some chemical compound, to some other one. You may be able to look up the structures of what you've started with, and what you end up with.