acids & bases svante arrhenius (1887) acids turn indicator dye litmus from blue to red react...
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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)
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
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