Chapter 10 Acids and Bases

Brønsted-Lowry acid

- a substance that is able to give a hydrogen ion, H+, to another molecule or ion. - a substance that accepts H+ from an acid. • Acids are proton donors. • The reaction need not occur in water, and a Brønsted- Lowry acid need not give H+ ions in water.

strong weak bases strong acids

-_____ acids give up a proton easily and are essentially 100% dissociated in water. • _____ acids give up a proton with difficulty and are substantially less than 100% dissociated in water. • Weak _____ have little affinity for a proton. • _____ bases grab and hold a proton tightly. • Polyprotic ______ undergo stepwise dissociations in water. • The first dissociation occurs to the extent of nearly 100%. • The second dissociation takes place to a much lesser

conjugate acid-base pairs

Pairs of chemical species such as HBr, Br- and H2O, H3O+

amphoteric

Substances which can react as either an acid or a base

products

The ______of an acid-base reaction can also behave as acids and bases. • Many acid-base reactions are reversible.

1

The ratio of [HA] to A- should be close to ____

titration

The total acid or base concentration of a solution is found by carrying out a _____

water

_____ can act as both an acid and a base.

water yields water concentration

_____can dissociate to form hydronium and hydroxide ions. • Because each dissociation reaction ______ one H3O+ ion and one OH- ion, the concentrations of the two ions are identical. • The ion-product constant for ____ (Kw) is the H3O+ and OH- molar concentrations in water or any aqueous solution times the OH- concentration. Kw = [H3O+][OH-] = 1.00 × 10-14 • We can determine the concentration of one species, if we know the ______ of the other.

acid

a substance that produces hydrogen ions, H+, when dissolved in water. HCl ----> H+ + Cl-

base

a substance that produces hydroxide ions, OH-, when dissolved in water.

Buffer

mixtures of a weak acid and its conjugate base. Example: Acetic acid and sodium acetate • _____ solutions maintain the pH of blood and other fluids within narrow limits. • If OH- is added to this solution, the pH increases only slightly; the acid component of the buffer neutralizes the added OH-. • If H+ is added to this solution, the pH decreases only slightly; the base component of the____neutralizes the added H+.

Henderson- Hasselbalch equation

pH of a buffer can be expressed using the _________:

sour citric slippery

• Acids generally have a ____ taste: • Lemons, oranges, and grapefruit contain ___ acid, and sour milk contains lactic acid. • Bases are _____ and present in many household cleaning agents. • Sulfuric acid, H2SO4 (a strong acid) • Hydrochloric acid, HCl (a strong acid) • Nitric acid, HNO3, is a strong oxidizing agent. • Acetic acid, CH3CO2H (a weak acid) • Phosphoric acid, H3PO4 (a weak acid) • Sodium hydroxide, NaOH, caustic soda or lye, (a strong base) • Calcium hydroxide, Ca(OH)2, or slaked lime • Magnesium hydroxide, Mg(OH)2 • Ammonia, NH3 (a weak base)

acid 1 H

• Different _______ can supply different numbers of H+ ions. • Acids with ____ proton (HCl) are monoprotic acids. • H2SO4 is diprotic because it has two protons to donate. • H3PO4 is triprotic because it has three protons to donate. • Acidic ___ atoms are bonded to electronegative atoms.

aqeous

• The pH of an _____ solution is a number, usually between 0 and 14, that indicates the H3O+ concentration of the solution. pH = -log[H3O+] or [H3O+] = 10-pH • pH <7, an acidic solution. • pH >7, a basic solution. • pH =7, a neutral solution. [H3O+] = 4.6 x 10-3 M (two significant figures) pH = 2.34 (two digits after the decimal) For a solution of known pH, [H3O+] can be Calculated If the pH of a solution is 8.50, what is the [H3O+]? [H3O+] = 3.2 x 10−9 M

acid-base paper

• The simplest but least accurate method of pH determination is ____ indicators. These change color depending on the pH of the solution. • Test kits contain a mixture of indicators known as universal indicator that give approximate pH measurements in the range 2-10. • pH ____ makes it possible to determine pH simply by putting a drop of solution on the paper and comparing the color that appears to the color on a calibration chart. • A much more accurate way to determine pH is an electronic pH meter. Electrodes are dipped into the solution, and the pH is read from the meter.