In the equation: #A + B -> C+D#, what are A and B?
In a chemical equation you have
The reactants are the compounds which react to make the products.
For any chemical reaction, we write the chemical equation with the
[In the case where the reaction progresses to a state of equilibrium, you'll often see the arrow pointing in both directions (
#underbrace("A+B")_ "Reactants" => underbrace("C+D") _"Products"#
Example: for mass/mass calculations in equations...
#underbrace( overbrace("45.0 g")^(color(blue)("mass of Mg")) + overbrace(?color(white)(.)"g")^(color(blue)("mass of O"_ 2)))_ (color(purple)("the mass of the reactants")) => underbrace( overbrace("74.62 g")^(color(blue)("mass of MgO")))_ (color(purple)("the mass of the product"))#*
(*Underbrace formatting from Stefan V post.)