Transcript Acids and Bases Part II

Tuesday, May 20th (P1/2)
• PDN:
• Name H(NO3) and HI
• Write the formula for zinc (II) hydroxide and phosphoric acid
• Daily Log:
• Review Naming Acids and Bases
• Take Home due tomorrow
• Quiz on Thursday!
Tuesday, May 20th (P 6/7)
• PDN:
• Name Co(OH)3
• Write the formula for nitrous acid
• Daily Log:
• Review Naming
• Quiz Tomorrow
• pH notes
Section 20.2
Hydrogen Ions and Acidity
• OBJECTIVES:
• Given the hydrogen-ion or
hydroxide-ion concentration,
classify a solution as neutral,
acidic, or basic.
Section 20.2
Hydrogen Ions and Acidity
• OBJECTIVES:
• Convert hydrogen-ion
concentrations into values of pH,
and hydroxide-ion concentrations
into values of pOH.
pH
• pH is a measure of
the acidity or basicity
of an aqueous
solution.
Logarithms and the pH concept
• definition: pH = -log[H+]
• (Logarithms are powers of ten.)
Neutral solution: pH = 7
• Acidic solution: pH = less than 7
• Basic solution: pH= greater than 7
pH and pOH
• pOH = -log [OH-]
• pH + pOH = 14
• Basic Solution: pOH = less than 7
• Acidic Solution: pOH = greater than 7
Calculation Practice
What is the pH and pOH of a 1.2 x 10-3 M HBr solution?
FIRST ASK YOURSELF: IS HBr AN ACID OR A BASE?
Calculation Practice:
• What is the pH and pOH of a 2.34 x 10-5 M NaOH
solution?
FIRST ASK YOURSELF: IS NaoH AN ACID OR A BASE?
Calculation Practice:
• Determine the [H3O+] of a solution with a pH of 2.81
• Determine the [OH-] of a solution with a pH of 11.21
Calculation Practice
• Determine the pH of a magnesium hydroxide solution in
which 17.1 grams are dissolved in 1L.
Measuring pH
• Why measure pH?
• Everything from swimming pools, soil
conditions for plants, medical
diagnosis, soaps and shampoos, etc.
• Sometimes we can use indicators,
other times we might need a pH meter
Acid-Base Indicators
• An indicator is an acid or base that
undergoes dissociation in a known pH
range, and has different colors in
solution (more later in chapter)
• Examples: litmus, phenolphthalein,
bromthymol blue:
Acid-Base Indicators
• Although useful, there are limitations
to indicators:
• usually given for a certain
temperature (25 oC), thus may
change at different temperatures
• what if the solution already has
color?
• Ability of human eye to distinguish
colors
Acid-Base Indicators
• A pH meter may give more definitive
results
• Gives numerical pH values
• some are large, others portable
• works by measuring the voltage
between two electrodes
• needs to be calibrated