# Lab 5

```The MicroLAB™ Interface:
Plotting Measured Data to Generate
a Graph
Lab 5
Purpose
• You will learn to use
MicroLAB™ for data
acquisition and analysis.
• A graphical representation
of temperature and pH
changes will demonstrate
chemical changes related
to acid-base reactions.
pH
• The pH scale ranges from 0
to 14.
• The pH of a solution tells us
if that solution is acidic,
basic or neutral.
Acids
• Acids are compounds that
donate H+ to a solution.
• The pH of an acid always
falls below 7.
• The stronger the acid, the
closer the pH is to 0.
• HCl (hydrochloric acid) is
considered a strong acid.
• What is an example of
another strong acid?
Bases
• Bases are compounds that
donate OH- to solutions.
• The pH of bases always fall
above 7.
• The stronger the base, the
closer the pH is to 14.
• NaOH (sodium hydroxide) is
considered a strong base.
• What is an example of
another strong base?
Neutral Solutions
• Neutral Solutions have a
pH of 7.
• These solutions are neither
acidic nor basic.
• Water is considered
“neutral.”
• What is an example of
another neutral
compound?
Comparison of pH, [H+], and [OH-]
Acid-Base Reactions
HCl(aq) + NaOH(aq) → H2O(l) + Na+(aq) + Cl-(aq) + heat
•A strong acid and a strong base react to produce
water and a salt (neutralization). This process
releases heat (exothermic reaction).
•We can measure the change
in temperature that takes place.
•We can measure the pH change.
Calculations
• You can determine the
volume of base needed to
today by using the
equation MaVa = MbVb
• You must know the values
for the other three
variables first.
Calculations
•
•
•
•
Ma = 0.25* M HCl
Va = 85.0 mL
Mb = 0.25* M NaOH
Vb = Unknown
 Va   Ma   85.0mL   0.25 *M
Vb =
Mb 
 0.25 * M
*Get the exact number from
the appropriate carboy!
pH and Temperature Probes
– Be careful! The pH probes are
fragile.
– You will use a pre-calibrated
template for the temperature
probe.
– Remember to rinse and dry the
probes before each transfer. This
will prevent cross-contamination.
– Your instructor will show you how to
set up your probes and glassware.
Safety Concerns
• Reagents:
– HNO3 (1 N) / HCl (0.2 N)
– NaOH / KOH
• Eye Contact:
– Irritating, burns, permanent eye damage, tearing,
redness, pain, impaired vision, blindness
• Skin Contact:
– Irritating, redness, pain, soreness, severe skin burns,
ulcers, stains, destruction, scaling, and blistering
• Inhalation:
– Breathing difficulties, pneumonia, pulmonary
edema, coughing, choking, irritation of nose,
throat, and respiratory tract, burns, and death
• Ingestion:
– Pain and burns of the mouth, throat, esophagus and
gastrointestinal tract. Corrosive to mucous
membranes, perforation of the esophagus and
stomach, abdominal pain, nausea, vomiting,
abnormal sensations of hands and feet, and general
gastro-intestinal upset.
Waste and Solutions
• Conserve distilled water during
cleanup!
• Only neutral solutions can go
down the sink after you are