ACID-BASE NEUTRALIZATION
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A neutralization reaction is a double displacement reaction between an acid and a base to produce a salt and water. The salt is
formed from the negative ion of the acid and the positive ion of the base. When just enough base is added to react exactly with
the acid in a solution, we say the acid has been neutralized.
NEUTRALIZATION: ACID + BASE → SALT + WATER
The effects of the acid and base are destroyed by the neutralization. The salt produced will determine the pH of the resulting
solution.
Ex: HCl + NaOH → NaCl + H2O
Ex: H2SO4 + 2NaOH → Na2SO4 + 2H2O
Notice in this reaction that complete neutralization takes place. The H2SO4 is polyprotic (has more than one hydrogen) however
all the protons are given away in the neutralization. We will consider all the acid-base reactions to be complete for polyprotic
acids when mixed with a strong base. All H+’s in a polyprotic acid are neutralized when neutralized by a strong base...OH- is
such a strong base that it will react completely with all of the H+ ions in solutions of strong acids.
In the case of a weak acid and hydroxide base, OH- is such a strong base that it will react completely with any weak acid that it
encounters and neutralizes all the H+ in that acid.
Ex. Show the complete molecular, complete ionic, and net ionic equations for the reaction of acetic acid and sodium
hydroxide. Even though acetic acid is a weak acid and does not ionize very strongly, the OH- neutralizes all of its H+ ions.
Molecular: HC2H3O2(aq) + NaOH(aq) → NaC2H3O2(aq) + H2O(l)
Complete ionic: HC2H3O2 + Na+ + OH− → Na+ C2H3O2− + H2O
Net ionic: HC2H3O2 + OH− → C2H3O2− + H2O
Ex: Write molecular, complete ionic, and net ionic form of the equation for the neutralization reaction between
phosphoric acid and sodium hydroxide.
NOTE: The special case of weak base ammonia NH3. Because there is no OH- ion , the reaction is:
HCl + NH3 → NH4Cl
Notice that there is no H2O produced in the reaction.
In the following neutralization reactions, predict the products and name the salt that is formed. Make sure that all reactions are
balanced. These are complete neutralizations. Rewrite the entire reaction in the box provided.
1.
H2SO4 + Ca(OH)2 →
2.
HC2H3O2 + LiOH →
3.
Nitric acid + magnesium hydroxide →
4.
Sulfuric acid + ammonium hydroxide →
5.
HCl + KOH →
6.
Phosphoric acid + barium hydroxide →
7.
H3PO4 + Ca(OH)2 →
Show the balanced neutralization reactions between the acid and base that would form each of these salts.
1.
Sodium chloride
2.
Potassium sulfate
3.
Lithium nitrate
4.
Magnesium chloride
5.
Calcium chloride
6.
Barium sulfate
7.
Sodium carbonate
8.
Lithium sulfite
9.
Ammonium nitrite
10. Ammonium carbonate
11.
Sodium sulfate
12. Potassium fluoride
ACID-BASE NEUTRALIZATION – QUANTITATIVE STUDIES
There is a point where the acid has been completely neutralized or reacted by the base. This point is called the
EQUIVALENCE POINT. At the equivalence point, the acid and base no longer exist; only the salt and water. This
involves stoichiometry to determine the equivalence point in neutralization.
Note: In the calculations below, MA = Molarity of the acid MB = Molarity of the base.
VA = Volume of the acid VB = Volume of the base.
One of the most important formulas you will use is a variation of the molarity formula.
Molarity = moles/volume
therefore, MOLES = MOLARITY x VOLUME
EXAMPLE PROBLEMS
STEPS IN SOLVING NEUTRALIZATION PROBLEMS:
• Write the balanced equation.
• Identify and list all knowns and unknowns (to eliminate the words). Use abbreviations like MA, VB, molesA, etc.
• Determine the relationship of moles of acid to moles of base.
• Use stoichiometry to solve.
Ex. 1: How many moles of NaOH are needed to completely neutralize 0.250 moles of hydrochloric acid?
Ex. 2: What volume of 0.0947M NaOH is needed to neutralize 21.4 mL of 0.106M HCl?
Ex. 3 In a certain experiment, 28.0 mL of 0.250 M nitric acid and 53.0 mL of 0.320 M potassium hydroxide are
mixed. Calculate the amount of water formed in the resulting reaction. What is the concentration of H+ and OHin
excess after the reaction goes to completion? (0.123M)
ASSIGNMENT:
1)
Calculate the mass of potassium hydroxide needed to prepare 250 cm 3 of a 0.200 mol dm-3 solution.
2) What is the molarity of Ca(OH)2 if 200.00 mL of Ca(OH)2 is required to completely neutralize 100.00 mL of
0.350M H3PO4?
3) Calculate the mass of magnesium sulfate heptahydrate required to prepare 0.100 dm 3 of a 0.20 mol dm-3 solution.
4) What concentration of HCl will be required if you use 100.0 mL of that acid to neutralize 0.010L of 3.0M sodium
hydroxide?
5) Calculate the number of moles of chloride ions in 0.250 dm3 of 0.020 mol dm-3 zinc chloride solution.
6) What volume of 5.0M H2SO4 is required to neutralize a NaOH solution in which 2.50 g of NaOH has been
dissolved in water to produce 100.0 mL of NaOH solution?
7) Determine the molarity of H3PO4 solution in which 40.0 mL of the acid has been neutralized by 120.0 mL of
0.531M NaOH. Consider only one replaceable hydrogen in H3PO4. (This is not a complete neutralization!)
8) 0.275 grams of solid NaOH was added to 35.4 mL of HCl. Complete neutralization occurred. What was the
molarity of the HCl?
9) What would be the volume of 0.250M monoprotic acid required to react with 0.500 grams of Ca(OH)2?
10) What would be the molarity of a solution prepared by diluting 250.0 mL of 0.400M sulfuric acid with 1000 mL of
water?
11) A solution was prepared by dissolving 25.0 grams of Ba(OH)2 in water to make one liter of solution. How many
milliliters of 0.200M H2SO4 would be required to react with 25.0 mL of the Ba(OH)2 solution?
12) What is the molarity of an oxalic acid (H2C2O4) solution if 22.50 mL of this solution requires 35.72 mL of 0.198
M NaOH for complete neutralization?
13) In the reaction of H2SO4 with lithium hydroxide, only one of the acidic protons is neutralized. What volume of
0.750M LiOH would be required to neutralize only one proton of 150.0 mL of 0.400M H2SO4?
(a) What volume of 0.400M acid would be required to completely neutralize 200.0 mL of 0.250M base to produce
the salt magnesium chloride?
(b) What is the mass of salt produced?
(c) What is the mass of water produced?
14) What is the molarity of phosphoric acid if 15.0 mL of the acid is completely neutralized by 38.5 mL of 0.15M
NaOH?
15) What volume of 2.00M ammonium hydroxide would be required to completely neutralize 150.0 mL of 3.00M
carbonic acid?