Other Conversions (like Volume and Heat)

Here's some more of those good ol' conversions.

Volume at STP can be found using the conversion factor 22.4 L/mol. In chemical reactions, HEAT can be included as a separate term... this is called Enthalpy
Reactions that release heat are exothermic
Reactions that absorb heat are endothermic

Here are some examples of converting to/from volume! It's very very similar to previous conversions... just remember to use 22.4 L/mol!

Ex. 1:
Find the mass of sodium required to produce 5.68 L of hydrogen gas at STP from the reaction described by the following equation:
2Na + 2H2O -> 2NaOH + H2   Here the balanced equation is written out for you

5.68 L H2   x     1 mol    x    2     x    23 g    =   11.7 g       

                            28 g          1          1 mol   
ALWAYS convert the volumes to moles first. You cannot go from volume to mass

Ex 2:
How many litres of Oxygen are necessary for the combustion of 425 g of sulfur, assuming that the reaction occurs at STP?

 S + O2 -> SO2                Write out the balanced equation first.

425 g S  x   1 mol    x   1    x    22.4 L    = 297 L    Remember, convert to moles first!

                     32.1 g       1           1 mol