6.8 CHAPTER 6. QUANTITATIVE ASPECTS OF CHEMICAL CHANGE
- In a balanced chemical equation, the numberin front of the chemical symbols describes the
mole ratio of the reactants and products.
- The empirical formula of a compound is an expression of the relativenumber of each type of
atom in the compound.
- The molecular formula of a compound describes the actual number ofatoms of each element
in a molecule of the compound.
- The formula of a substance can be used to calculate the percentage by mass that each element
contributes to the compound.
- The percentage composition of a substance can be used to deduce its chemical formula.
- One mole of gas occupies a volume of 22.4 dm^3.
- The concentration of a solution can be calculated using the following equation,
C =
n
V
where C is the concentration (in mol.dm−^3 ), n is the number of moles of solute dissolved inthe
solution and V is the volume of the solution (indm^3 ).
- Molarity is a measure of the concentration of a solution,and its units are mol.dm−^3.
- Stoichiometry is the calculation of thequantities of reactants and products in chemical reactions.
It is also the numerical relationship between reactants and products.
- A limiting reagent is the chemical that is used up first in a reaction, and which therefore deter-
mines how far the reaction will go before it hasto stop.
- Anexcessreagent is a chemical that is in greater quantity than the limiting reagent in the reaction.
Once the reaction is complete, there will still be some of this chemicalthat has not been used
up.
