# In the equation: A + B -> C+D, what are A and B?

Jun 12, 2017

Reactants

#### Explanation:

In a chemical equation you have

Reactants $\rightarrow$ Products

The reactants are the compounds which react to make the products.

Jun 12, 2017

$A$ and $B$ are called the reactants of the chemical reaction.

#### Explanation:

For any chemical reaction, we write the chemical equation with the sfcolor(red)("reactants" on the sfcolor(red)("left side", the sfcolor(blue)("products" on the sfcolor(blue)("right side", and the reaction arrow between them, pointing most often to the right, to indicate that the reaction progresses from reactants to products.

[In the case where the reaction progresses to a state of equilibrium, you'll often see the arrow pointing in both directions ($r i g h t \le f t h a r p \infty n s$) to indicate that the rate of the forward reaction (reactants form the products) is the same as the rate of the reverse reaction (products form the reactants)].

Jun 12, 2017

$\text{Reactants" => "Products}$

#### Explanation:

underbrace("A+B")_ "Reactants" => underbrace("C+D") _"Products"

Example: for mass/mass calculations in equations...

$2 M {g}^{o} \left(s\right) + {O}_{2} \left(g\right) \implies 2 M g O \left(s\right)$

$\underbrace{\overbrace{\text{45.0 g")^(color(blue)("mass of Mg")) + overbrace(?color(white)(.)"g")^(color(blue)("mass of O"_ 2)))_ (color(purple)("the mass of the reactants")) => underbrace( overbrace("74.62 g")^(color(blue)("mass of MgO")))_ (color(purple)("the mass of the product}}}$*

(*Underbrace formatting from Stefan V post.)