Transcript Introduction to pH - Kramersworld's Weblog

Introduction to pH
LAB-AIDS pH Kit #80
pH
• Living things have certain pH ranges for
normal biochemical processes to occur.
• pH is a logarithmic scale for measuring
acids and bases video
• Measured through indicators or pH meter
Properties of Acids & Bases
• Acid
• Base (Alkaline)
– Taste tart or sour
– Taste bitter
– Conduct electricity
– Feel slippery
– Have more hydronium
– Have more hydroxide
ions
ions
– H3O+
– OH–Buffers are chemicals that neutralize the effects of
adding small amounts of either an acid or a base to a
solution.
Strongest acid
Weak acid
Neutral
Weak Base
Strongest base
If “Normal
rain water”
is pH 6, then
what would
the pH of
acid rain be?
SAFETY
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NO tasting, smelling, touching of liquids
NO tasting, smelling of papers
NO wandering – be aware while cleaning up.
Everyone wears goggles to protect eyes from
splashes
• One person from team wears gloves while
handling materials
• First Aid – wash affected area with plenty of
water.
CLEANUP
• Use toothpicks to remove pH paper.
Throw toothpicks and pH paper in white
barrel near sink
• Pour contents of Chemplate into the
BEIGE water basin
• Dip the Chemplate into the GREEN bucket
5x
• Rinse Chemplate out in RUNNING water
• Leave Chemplate on counter
Data Table
• Create a data table to account for:
– Material tested (6 items)
– Cavity number (#)
– Original color
– Color change for acid (HCl)
– Color change for base (NaOH)
Lab Setup
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•
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Setup the Chemplate as follows:
Phenol red: one drop in cavities 1 and 2
Phenolphthalein: one drop in cavities 5 and 6
Bromthymol Blue: one drop in cavities 9 and 10
Red litmus paper: ¼” square in cavities 3 & 4
Blue litmus paper: ¼” square in cavities 7 & 8
Universal pH Indicator paper: ¼” square in
cavities 11 & 12
Lab Procedure
• Add one drop of dilute Hydrochloric Acid (HCl) to cavities
1,5, and 9. Stir with toothpick.
• Add one drop of dilute Sodium Hydroxide (NaOH), a
base to cavities 2,6, and 10. Stir with toothpick.
• Record data into table.
• For paper strips in cavities 3 and 7 add one drop of HCl.
Record data into table.
• For paper strips in cavities 4 and 8 add one drop of
NaOH. Record data into table.
• Cavity 11 – 1 drop of HCl; Cavity 12 – 1 drop of NaOH.
Compare color to pH scale on vial.
Post Lab Questions
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How do you think litmus paper is made?
Of what value is Universal pH Indicator paper?
How do you think Universal pH Indicator paper is made?
A student pH tests several items and is asked to place
the results in order of strongest acid to weakest acid.
What should the results look like? Values are 6.7, 7.0,
3.5, 4.2, 8.9, 2.0, and 13.
• Add to your notes – What color do acids turn blue litmus
paper? Red litmus paper? What color do bases turn
blue litmus paper? Red litmus paper?
Lab Materials
Before & After Photos
Chemplate after
setup / prior to
procedure
Chemplate after
procedure is
finished