March 7- Stoichiometry Calculation

Today we did stoichiometry calculations involving Molarity and STP.

Molarity is easily defined by this one equation. Molarity=  Moles
                                                                                   Litres

STP is 22.4 litres/mole

Example

1. How many moles of nitrogen gas is needed to react with 44.8 liters of hydrogen gas to produce ammonia gas?

3H₂   +   N₂    2NH₃
GIVEN: 44.8 L of H₂ at STP.
FIND: mols of N₂.
Here the sequence is: GIVEN liters of H₂ at STP, CHANGE liters of H₂ at STP to mols of H₂, MOL RATIO to change from H₂ to N₂. There is no need to go any further to change the N₂ into mols, because the mol ratio leaves the material in that unit anyway.






How many liters of ammonia are produced when 89.6 liters of hydrogen are used in the above reaction?
The "above reaction" from problem #1 is: N₂   +   3H₂    2NH₃

GIVEN: 89.6 L of H₂ at STP.
FIND: Volume of ammonia (in liters at STP)
Take the GIVEN quantity, use the Molar Volume of Gas at STP (MVG) to change it to mols, change the material with the mol ratio (MR), and change the mols of new material to the requested liters at STP using the MVG again.