The Acid Test
Name: ____________________________________________ Score: _____/10
1. Put on goggles upon entering the lab.
2. Obtain a vial of pH paper and a well plate. Your teacher will show you what a well plate looks like.
3. At your station, take 5 drops of each concentration sample of HCl (hydrochloric acid) or if someone else is using the HCl,
begin with the NaOH (sodium hydroxide). There are six different concentrations of each. When completed you should have
twelve wells with five drops in each.
4. Pull out one trip of pH paper being careful to touch it only on the edges.
5. Dip one end of the pH paper in the sample. Keep holding the one end of the pH paper that is not in the sample. Compare it
to the color code chart on the pH paper vial. Record the pH in the data table. Return the sample to its original location.
6. Repeat steps 4 and 5 until you have tested all the samples. Use a clean, dry piece of pH paper for every sample. Use both
ends of the pH paper before discarding it in the trashcan. You should have two samples tested with one strip of pH paper—
test one sample on each end.
7. Put one drop of universal indicator (a substance that changes color at different pH values) in each well. Record the color and
compare with the pH color chart on the pH paper vial for a similar approximate pH value.
8. Clean up your area and get your teacher’s initials when you have done so. Don’t forget to wash your hands using soap and
warm water before leaving the lab and definitely before eating!
___________________ (teacher’s initials)
9. Complete the graph and questions.
Acid or Sample Concentration Concentration Hypothesize pH reading Color of sample pH reading
Base? in Scientific what you from the pH w/universal indicator from
Notation believe the paper universal
pH will be indicator
Graph 1: Graph the pH of the acid vs. its concentration
a) Title the graph
b) Label and scale the x-axis for the concentrations (mol/L or M)
c) Label the y-axis for the pH values (there are no units for pH values)
d) Plot the points of the graph
e) Connect the dots (do NOT use a best fit line)
Graph: 2: Graph the pH of the BASE vs. its concentration
f) Title the graph
g) Label and scale the x-axis for the concentrations (mol/L or M)
h) Label the y-axis for the pH values (there are no units for pH values)
i) Plot the points of the graph
j) Connect the dots (do NOT use a best fit line
Graph 1: Graph the concentrations of the acids and bases against the pH values using a BAR GRAPH
k) Title the graph
l) Label and scale the x-axis for the concentrations (mol/L or M)
m) Label the y-axis for the pH values (there are no units for pH values)
n) draw the bars for each sample; be careful not to put the bars next to each other—allow at least one blank
column between each sample
o) Color in the bar with the same color (or as close as you can) as the concentration turned with the universal