If you mix NaOH and HCl, both having 45.0mL of volume, which of the two is the limiting reactant?
1 Answer
You can't tell without knowing the molarities of the two solutions.
Explanation:
Sodium hydroxide,
The balanced chemical equation for this neutralization reaction looks like this
#"NaOH"_text((aq]) + "HCl"_text((aq]) -> "NaCl"_text((aq]) + "H"_2"O"_text((l])#
Notice that you have a
In order to be able to determine which of the two reactants is a limiting reagent, you need to know how many moles of each you have.
When mixing two solutions of equal volumes, like you have here, the mole ratio becomes equivalent to a concentration ratio.
You know that a solution's molarity is defined as
#C = n/V" "# , where
In your case, you would have
#C_"HCl" = n_"HCl"/V " "# and#" "C_"NaOH" = n_"NaOH"/V#
This is equivalent to
#V = n_"HCl"/C_"HCl" implies n_"NaOH"/C_"NaOH" = n_"HCl"/C_"HCl"#
The mole ratio between sodium hydroxide nd hydrochloric acid is
#n_"NaOH"/n_"HCl" = C_"NaOH"/C_"HCl"#
Since equal volumes of equal concentration solutions will have equal numbers of moles of each reactant, it follows that the solution that has the lower concentration will act as a limiting reagent.
So remember, when you add equal volumes of each reactant, their respective molarities will determine which one acts as a limiting reagent and which one is in excess.