What we are doing NOW…
Turning in, stapled and IN ORDER:
Lab #2: The Scientific Method
Pre-Lab exercise (41 & 42), LAB QUESTIONS (49-51)
Sticker for completed work but NOT to tear
out:
Lab #3: Investigations into Properties of
Solution pH and Conductivity
Pre-Lab exercise (62-65)
Due NEXT CLASS:
• Lab #3: Investigations into Properties of Solution
pH and Conductivity
– Pre-Lab exercise (62-65)
– LAB EXCERISES with REVIEW QUESTIONS (66-68)
• Lab #4: What’s in Our Food?
– Pre-Lab exercise to check for completion (75-77)
Tuesday, March 3
Thursday, February 26
Friday, February 27
503
501
502
551
506
550
HEADS UP for Extra Credit opportunity
Article and summary about nutrition
OR
My Food Plan (with synopsis)
Due in TWO weeks
Part I: Testing the pH of diluted acid
• Make a serial dilution of 0.1 M HCl.
1 mL
1 mL
A
.1M HCl
pH 0
1 mL
B
1 mL
1 mL
C
D
E
pH 2
pH 3
pH 4
pH 5
9 mL
of H2O
9 mL
of H2O
9 mL
of H2O
9 mL
of H2O
9 mL
of H2O
A
pH 1
• What is the independent variable you have created?
• The dependent variable?
• What is being held constant?
Part I: Testing the pH of diluted acid
Once the solutions have been made and you have recorded your
predictions, place the pH strips on a paper towel to make the pH
observation. Write the solution version above the pH paper.
A
B
C
D
E
Part II: Conductivity Test
• Prepare 0.1 M glucose solution and 0.1M salt solution
• Test the conductivity of glucose, salt, acid and base solutions
Particles dissolved =
solute
Water = solvent
Part II: Solutions, Dilutions!
If you are given: 100mL of a 0.1 M glucose solution…
molar mass* X desired molarity X desired volume in Liters
= number of grams of solute
(C6H12O6 {180g/mol}) X (0.1mol/L) X (.1L) =
__1.8 g___
* Use the periodic chart on page 70
Part II: Solutions, Dilutions!
How do you prepare 100 mL of 0.25 M HCl
from a 6 M acid stock solution?
(C1) (V1) = (C2) (V2)
Additional Homework:
How do you prepare a 100 mL of 0.5 M NaCl solution
from a 3 M salt stock solution?
Part III: Testing Buffers
Test Tube 1:
• 5 mL of water
Test Tube 2:
• 5 mL of
phosphate buffer
• 10 mL of water
• ? drops of
Phenol Red
for change
• ? drops of
Phenol Red
for change
Phenol red is a color indicator.
At neutral, it is color red, acidic environment = yellow, basic environment = purple.
Let’s get to WORK!!!
I will demonstrate part III
for you after parts I and II
(so there will be one less lab for you to clean up).
Be sure to CAREFULLY review your
procedures, take notes on what occurs,
and carefully clean/dry your materials
before placing them back in the bin.