Reactions in Aqueous Solution

Chapter 4 – Part 3

Acid Base Reactions

Proton Transfer ReactionsAKA - Neutralization

Acids: Substances that

increase the concentration of H+ when dissolved in water (Arrhenius).

Proton donors (Brønsted–Lowry).

AcidsThere are only seven strong acids:

Monoprotic acids

HCl H+ + Cl-

HNO3 H+ + NO3-

CH3COOH H+ + CH3COO-

Strong electrolyte, strong acid

Strong electrolyte, strong acid

Weak electrolyte, weak acid

4.3

Diprotic acidsH2SO4 H+ + HSO4

-

HSO4- H+ + SO4

2-

Strong electrolyte, strong acid

Weak electrolyte, weak acid

Triprotic acidsH3PO4 H+ + H2PO4

-

H2PO4- H+ + HPO4

2-

HPO42- H+ + PO4

3-

Weak electrolyte, weak acid

Weak electrolyte, weak acid

Weak electrolyte, weak acid

4.3

Bases: Substances that

increase the concentration of OH− when dissolved in water (Arrhenius).

Proton acceptors (Brønsted–Lowry).

Bases

The strong bases are the soluble salts of hydroxide ion:

Neutralization ReactionsGenerally, when solutions of an acid and a base are combined, the products are a salt and water.

HCl (aq) + NaOH (aq) NaCl (aq) + H2O (l)

Salts are less reactive than acids and bases.

Why do they do that?

Neutralization ReactionsWhen a strong acid reacts with a

strong base, the net ionic equation is…

HCl (aq) + NaOH (aq) NaCl (aq) + H2O (l)

Gas-Forming Reactions Sometimes the expected product predicted

by just switching the ion partners decomposes to give a gaseous product (CO2 or SO2).

CaCO3 (s) + HCl(aq) CaCl2(aq) + CO2(g) + H2O (l)

NaHCO3(aq) + HBr(aq) NaBr(aq) + CO2(g) + H2O(l)

SrSO3(s) + 2 HI(aq) SrI2(aq) + SO2(g) + H2O(l)

Why do they do that?

Gas-Forming Reactions This reaction gives the predicted

product, but you had better carry it out in the hood, or you will be very unpopular!

Just as in the previous examples, a gas is formed as a product of this reaction:

Na2S (aq) + H2SO4 (aq) Na2SO4 (aq) + H2S (g)

Solution Stoichiometry

Count with Volume!

Molarity Two solutions can contain the

same compounds but be quite different because the proportions of those compounds are different.

Molarity is one way to measure the concentration of a solution.

moles of solute

volume of solution in litersMolarity (M) =

4.5

Making Solutions

M = molarity =moles of solute

liters of solution

What mass of KI is required to make 500. mL ofa 2.80 M KI solution?

4.5

Dilution is the procedure for preparing a less concentrated solution from a more concentrated solution.

Dilution

Add Solvent

Moles of solutebefore dilution (i)

Moles of soluteafter dilution (f)=

MiVi MfVf=4.5

How would you prepare 60.0 mL of 0.200 MHNO3 from a stock solution of 4.00 M HNO3?

4.5

Using Molarities inStoichiometric Calculations

Titration

The analytical technique in which one can calculate the concentration of a solute in a solution.

4.7

What volume of a 1.420 M NaOH solution isRequired to titrate 25.00 mL of a 4.50 M H2SO4 solution?