Reactions in Aqueous Solution Chapter 4 – Part 3

Acid Base Reactions Proton Transfer Reactions AKA - Neutralization

Acids: Substances that increase the concentration of H + when dissolved in water (Arrhenius). Proton donors (Brønsted–Lowry).

Acids There are only seven strong acids:

Monoprotic acids HCl H + + Cl - HNO 3 H + + NO 3 - CH 3 COOH H + + CH 3 COO - Strong electrolyte, strong acid Weak electrolyte, weak acid 4.3

Diprotic acids H 2 SO 4 H + + HSO 4 - HSO 4 - H + + SO 4 2- Strong electrolyte, strong acid Weak electrolyte, weak acid Triprotic acids H 3 PO 4 H + + H 2 PO 4 - H 2 PO 4 - H + + HPO 4 2- HPO 4 2- H + + PO 4 3- 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 Reactions Generally, when solutions of an acid and a base are combined, the products are a salt and water. HCl (aq) + NaOH (aq)  NaCl (aq) + H 2 O (l) Salts are less reactive than acids and bases. Why do they do that?

Neutralization Reactions When a strong acid reacts with a strong base, the net ionic equation is… HCl (aq) + NaOH (aq)  NaCl (aq) + H 2 O (l)

Gas-Forming Reactions Sometimes the expected product predicted by just switching the ion partners decomposes to give a gaseous product (CO 2 or SO 2 ). CaCO 3 (s) + HCl (aq)  CaCl 2 (aq) + CO 2 (g) + H 2 O (l) NaHCO 3 (aq) + HBr (aq)  NaBr (aq) + CO 2 (g) + H 2 O (l) SrSO 3 (s) + 2 HI (aq)  SrI 2 (aq) + SO 2 (g) + H 2 O (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: Na 2 S (aq) + H 2 SO 4 (aq)  Na 2 SO 4 (aq) + H 2 S (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 liters Molarity (M) =

4.5

Making Solutions M = molarity = moles of solute liters of solution What mass of KI is required to make 500. mL of a 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 solute before dilution (i) Moles of solute after dilution (f) = MiViMiVi MfVfMfVf = 4.5

How would you prepare 60.0 mL of M HNO 3 from a stock solution of 4.00 M HNO 3 ? 4.5

Using Molarities in Stoichiometric Calculations

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

4.7 What volume of a M NaOH solution is Required to titrate mL of a 4.50 M H 2 SO 4 solution?