 # Neutralization Reactions

## Presentation on theme: "Neutralization Reactions"— Presentation transcript:

Neutralization Reactions

Acid-Base Reactions If we mix a strong acid solution with a strong base solution we get a neutral solution that is neither acidic nor basic. For example: HCl + NaOH → NaCl + H2O H2SO4 + 2 KOH → K2SO4 + 2 H2O

Acid-Base Reactions Mixing a strong acid with a strong base gives us
water a salt the conjugate base of the acid plus the conjugate acid of the base In this case, a salt is an ionic compound of any kind.

Acid-Base Reactions In most cases, the net ionic equation of a neutralization reaction is: H3O+ + OH- → 2 H2O The salt that is formed usually stays in solution. The salt ions are spectator ions.

Titration Acids and bases combine in different ratios: 1:1
HCl + NaOH → NaCl + H2O 1:2 H2SO4 + 2 KOH → K2SO4 + 2 H2O 2:1 2 HCl + Ca(OH)2 → CaCl2 + 2 H2O

Titration The point where the number of mols of hydronium ions equals the number of mols of hydroxide ions is called the equivalence point. The stoichiometric ratio of the acid to the base in the balanced equation tells us where the equivalence point is.

Titration Example 1: How many mols of sulfuric acid are required to neutralize 0.50 mols of sodium hydroxide? nNaOH = 0.50 mol H2SO4 + 2 NaOH → Na2SO4 + 2 H2O nNaOH nH2SO4 2 1 1×nNaOH 2 0.50 mol 2 = nH2SO4 = = nH2SO4 = 0.25 mol

Titration A titration is a neutralization reaction under controlled conditions. We control the amounts of acid and base reacted while monitoring the pH of the reaction solution. When we reach neutralization (the equivalence point), we carefully measure the amounts of the acid and the base.

Titration A titration uses
a flask or beaker to hold the unknown solution a burette to hold the known (standardized) solution an indicator (added to the flask) to show the end of the titration.

Titration The burette shows the volume of titrant added to the flask.
We read the meniscus to find the amount added. Placing a white sheet with a black section below the meniscus can help to define the meniscus.

Titration We can use an indicator to show the equivalence point (end point) of the titration. We can also use a pH meter to find the end point by generating a pH curve.

Titration On the left, a strong base is added to a strong acid.
The equivalence point occurs at pH = 7.

Titration On the right, a strong acid is added to a strong base.
The equivalence point also occurs at pH = 7.

Titration nNaOH nNaOH nH2SO4 Example 2:
A 25-mL solution of H2SO4 is completely neutralized by 18 mL of 1.0 M NaOH. What is the concentration of the H2SO4 solution? MNaOH = 1.0 M VNaOH = 18 mL = L MH2SO4 = ? M VH2SO4 = 25 mL = L H2SO4 + 2 NaOH → Na2SO4 + 2 H2O nNaOH = MNaOHVNaOH = (1.0)(0.018) mol = 0.018 mol nNaOH nH2SO4 2 1 nNaOH 2 0.018 mol 2 = nH2SO4 = = = mol nH2SO4 VH2SO4 mol 0.025 L MH2SO4 = = = 0.36 M