Question

How do you calculate the moles of a product?

Answer 1

In order to calculate the moles of a product, you must know the mass of the product, and its molar mass (g/mol), which is the mass of one mole of of the product. You then divide the mass of the product by its molar mass.

Explanation:

Example:

Lets say you performed an experiment in which a double replacement reaction occurred and you obtained `"5.79g"` of solid silver chloride. The formula for silver chloride is `"AgCl"`.

The molar mass of an element is its atomic weight on the periodic table in grams/mol. The molar mass of `"Ag"` is `"107.8682g/mol"`, and the molar mass of `"Cl"` is `"35.45g/mol"`. The molar mass of `"AgCl"` is the sum of the molar masses of the silver and chlorine atoms, which equals `"143.32g/mol"`.

Known:

mass of product = `"5.79g"` `"AgCl"`
molar mass `"AgCl"` = `"143.32g/mol"`

Unknown:

moles of product `"AgCl"`

Solution:

Divide the mass of the product by its molar mass.

`(5.79color(red)cancel(color(black)("g")) "AgCl")/(143.32color(red)cancel(color(black)("g"))/"mol")="0.0404 mol AgCl"`