Upload
oliver-jenkins
View
237
Download
0
Embed Size (px)
Citation preview
Acids, Bases, & pH
I. Macroscopic Properties
Easily Observable
A. Acids taste sour, bases taste bitter
B. Bases feel slippery (soap)
C. Acids & Bases react with each other
Acid-Base Indicators
D. Acids & Bases cause certain dyes to change color. These dyes are called acid-base indicators.
E. . Example: Litmus changes red in acid & blue when exposed to bases
F. Red cabbage, radishes & rose petals
Macroscopic cont.
G. Reactions with metals & carbonates
1. Acids react with metals to form H2
**acids cause metals to corrode
2. Acids react with carbonates to form CO2 & water.
** This causes pollution & the wearing away of limestone & marble.
II. Submicroscopic Properties
A. Acids and Bases Acids have formulas that begin with an “H”.
They have an acidic hydrogen- a H atom that can be transfered to water and is written 1st in a formula.
1 acidic H = monoprotic, ex: HCl
2 acidic H = diprotic, ex: H2SO4
Acids are proton donors Produce hydronium ions [H3O+]
A. Acids and Bases
The general reaction for an acid dissolving in water is
Bases often have formulas that end in OH
Bases are proton acceptorsBases produce hydroxide
ions [OH-]
A. The pH Scale
•Neutral pH = 7[H3O+]=[OH-]
•Acids pH<7[H3O+]>[OH-]
•Bases pH>7[H3O+]<[OH-]
A. The pH Scale
Because the pH scale is a log scale based on 10, the pH changes by 1 for every power of 10 change in the [H+].
B. Acid Strength • Weak acid – most of the acid molecules remain intact
(HC2H3O2)
Common AcidsStrong acids
– Sulfuric acid, H2SO4
– Hydrochloric acid, found in gastric juice, HCl
– Nitric acid, HNO3
Weak acids
–Acetic Acid, found in vinegar, HC2H3O2,
–Carbonic Acid, found in soft drinks, H2CO3
–Phosphoric Acid, H3PO4
Common Bases
Strong bases are Group 1 or 2 metals bonded with hydroxide.
ex: Sodium Hydroxide - NaOHPotassium Hydroxide – KOHCalcium Hydroxide - Ca(OH)2
Weak BasesHousehold ammonia = Ammonium Hydroxide = NH4OH
Ammonia= NH3
C. Water as an Acid and a Base
Water is amphoteric – it can behave as either an acid or as a base
Ionization of water
– Concentration of hydronium and hydroxide are equal
C. Water as an Acid and a Base
Product of [H3O+] and [OH] is always constant.
A. The pH Scale
The “p scale” is used to express small numbers. pH = log [H+]
A. The pH Scale
A. The pH Scale
pOH scale
pOH = log [OH]
pH + pOH = 14.00
A. The pH Scale
B. Measuring pH
Indicators – substances that exhibit different colors in acidic and basic solutions
– In an acid solution the indicator will be in the HIn form.
– In a basic solution the indicator will be in the In form.
C. Calculating the pH of Strong Acid Solutions
Determine the [H+]. pH = log[H+]