A chemical problem may be presented to you in units of moles, mass, or volume. Which one of these can be directly used in arithmetic no matter what the conditions are?
4 answers
moles
Why moles?
The equations we write represent mols. For example,
2NaOH + H2SO4 ==> 2H2O + Na2SO4
It reads, "two moles of sodium hydroxyde reacts with one mole of H2SO4 to produce 2 moles of water and one mole of sodium sulfate." If we have grams, we must convert to moles first before calculating problems with stoichiometry (moles = grams/molar mass). It it is volume, we must convert to moles first before proceeding (volume/22.4 L = moles).
2NaOH + H2SO4 ==> 2H2O + Na2SO4
It reads, "two moles of sodium hydroxyde reacts with one mole of H2SO4 to produce 2 moles of water and one mole of sodium sulfate." If we have grams, we must convert to moles first before calculating problems with stoichiometry (moles = grams/molar mass). It it is volume, we must convert to moles first before proceeding (volume/22.4 L = moles).
What this says is that chemicals react by mole ratios, not by grams or by volumes.
1 answer