Acids & BasesSvante Arrhenius (1887) ACIDS Turn indicator dye litmus

from blue to red React with active metals

such as zinc, iron, and tin, dissolving the metal and producing hydrogen gas

Taste sour, if diluted enough to be tasted safely

React with certain compounds called alkalis or bases to form water and compounds called salts

BASES Turn the indicator dye

litmus from red to blue Feel slippery or soapy

on the skin Taste bitter React with acids to

form water and salts

Acids Arrhenius proposed that these characteristic

properties of acids are actually properties of the hydrogen ion (H+), and that acids are compounds that yield H+ in aqueous solutions. Slightly modified today

Hydronium ion (H3O+) For simplification, we’ll stick with the H+

terminology.

Acids Monoprotic

One H+

Diprotic Two H+

Triprotic Three H+

Polyprotic General term for acids

that give up more than one H+

Strong Acids Ionize completely (or

nearly completely) in water

HCl (hydrochloric acid)

Weak Acids Ionize only slightly in

water CH3COOH (acetic

acid)

Bases Yield hydroxide ions (OH-) in aqueous solutions

Monobasic One hydroxyl anion

Dibasic Two hydroxyl anions

Tribasic Three hydroxyl anions

Polybasic General term for bases that give up more than one OH-

Strong Bases Completely ionize

NaOH (sodium hydroxide; lye) All the bases of Group I and Group II are strong bases

Weak Bases NH3 (ammonia)

pH Scale pH = -log [H+]

Brønsted-Lowry Acid-Base Theory By the 1920’s chemists were working with

solvents other than water.

Acid Proton (H+) donor

Base Proton (H+) acceptor

Acid-Base Titrations Method used to

determine just how much acid (or base) there is in a solution of unknown concentration

Burette A piece of laboratory

glassware designed to deliver known amounts of liquid into another container

Acid-Base Titrations One mole of NaOH will react completely with

one mole of H+

Using volumetric analyses with a pH indicator, you can determine the moles of H+

A Word About Moles…. A mole used in chemistry is something

like the dozen we use every day.

A mole simply means that you have 6.02 x 1023 of whatever you’re talking about. Avogardo’s number

Molarity is defined as the number of moles of solute divided by the number of liters of solution Molarity (M) = moles of solute liters of solution

Water Hardness Calcium (Ca2+) Magnesium (Mg2+)

Why the concern?

Types of Water Hardness Temporary

Permanent

EDTA Ethylenediaminetetracetic acid

Chelating agent

Eriochrome Black T (EBT)

Example Calculations 50.0 mL sample of tap water analyzed

Beginning volume of EDTA = 22.57 mL End volume of EDTA = 6.23 mL

Amount of EDTA titrated = 16.34 mL

Questions:1. How many moles of EDTA were used?2. What is the molarity of metal ion present in the

water?3. What is the concentration of CaCO3 in ppm in the

water?

1. How many moles of EDTA were titrated?Molarity of EDTA = 0.01000 M

Moles of EDTA = (Molarity)(Liters of solution) = (0.01000 mol/L)(0.01634 L) = 0.0001634 moles EDTA = 1.634 x 10-4 moles EDTA

2. What is the molarity of the metal ion present in the water?

Molarity of metal ion = moles of EDTA liters of water sample

= 0.00001634 mol EDTA 0.050 L water

= 0.003268 mol/L of EDTA = 0.003268 mol/L metal

ions

3. What is the concentration of CaCO3 in ppm in the water?

CaCO3 ppm = Molarity of metal ion X molecular weight of Ca2+ X 1000 mg/g

CaCO3 ppm = 0.003268 mol/L X 40.08 g/mol X 1000 mg/g

CaCO3 ppm = 131 mg/L

= 131 ppm