Acid Base Reactions
The addition of an acid to a base is called a neutralization reaction.
In grade 10 you learned that a neutralization reaction produces salt and water
Eg. HCl(aq) + NaOH(aq) à ___________ + __________
This is true for many acid base reactions but not all…
Eg. HCl(aq) + NH3(aq) à ________ + _______ (notice that water is not produced)
In both cases, however, the acid and base react and neutralize each other. Equivalence point ­ the point in a neutralization reaction where there is _________________________________________ of the acid and base. Eg. for the following neutralization reactions
1) HCl(aq) + NaOH(aq) à NaCl(aq) + H2O(l)
equivalence occurs when nHCl nNaOH 2) H3PO4(aq) + 3KOH à K3PO4(aq) + 3H2O(l)
equivalence occurs when nH3PO4 nKOH Knowing when the equivalence point occurs during the reaction allows for the determination of the concentration of acids or bases. There is no visible sign of when the equivalence point occurs however. Titration ­ a lab technique used to quantitatively determine the _______________ of an acidic or basic solution of unknown concentration. Acid­base indicator: substance that changes ________ depending on the [H3O+] (i.e. on how acidic or basic the solution is). When added to a neutralization reaction, the appropriately chosen indicator will change colour at the equivalence point.
Endpoint ­ point during a titration when there is a ______________ (i.e. colour change of the indicator).
Titration technique video (see website)
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Titration Problems (use the mole highway to find the concentration of the unknown, write the balanced reaction first)
1) In a titration of 25.00 mL of H2SO4 was added to 32.15 mL of 0.00983 mol/L NaOH to reach the endpoint. Find the concentration of the acid. 2) A nitric acid solution requires 26.80 mL of 0.0950 mol/L KOH to neutralize 15.00 mL of the acid. Calculate the concentation of the acid.
3) A 25.00 mL volume of barium hydroxide is completely neutralized by 36.20 mL of 0.100 mol/L HCl. Find the concentation of the base.
4) 32.4 mL of 0.65 mol/L magensium hydroxide are required to reach equivalence with 55.0 mL of phosphoric acid. What is the concentration of the phosphoric acid?
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