How do you use stoichiometry to determine the volume of a gas at STP?

Stoichiometry is used to relate amounts of reactants and products in a chemical reaction. When gases are involved, we can use molar volume at STP to determine the volume.

At STP (Standard Temperature and Pressure: 0 °C and 1 atm), 1 mole of any gas occupies 22.4 liters. This is the key fact we use.

Steps to determine the volume of a gas at STP using stoichiometry:

1. Write the balanced chemical equation.
   – This tells you the mole ratio between reactants and products.
2. Convert the given quantity to moles.
   – If you’re given mass, use molar mass to convert to moles.
   – If you’re given particles, use Avogadro’s number.
3. Use the mole ratio from the equation.
   – Find how many moles of the gas are produced or required.
4. Convert moles of gas to volume.
   – Multiply the number of moles of gas by 22.4 L/mol at STP.

Example (no equations, just words):
Suppose hydrogen gas reacts with oxygen to form water. If you start with a certain number of moles of hydrogen, the balanced equation shows how many moles of oxygen are needed and how many moles of water form. For any gas in the reaction, you can multiply its moles by 22.4 to get the volume at STP.