Is it Acidic or Alkaline?
Name________________________________
In chemistry, pH is a measure of the acidity or alkalinity (basic) of a solution. pH can be approximated
by a logarithmic formula (base 10) of the molar concentration of dissolved hydronium ions (H3O+). A
low pH indicates a high concentration of hydronium ions, while a high pH indicates a low
concentration. An acid solution has a pH < 7, while a basic solution (alkaline) has a pH > 7. Pure
water has a neutral pH of 7.
pH
log( H 3O )
Questions:
1. A science textbook shows this formula to be pH
log10
1
H 3O
. Using the properties
associated with logarithms, show that the two formulas are equivalent.
2. Due to the citric acid, the pH level of orange juice is typically 3.5. What is the concentration of
hydronium ions in orange juice? Would you describe this has a high, or low, concentration?
3. What is the pH level of bleach if its concentration of hydronium is 2.5 x 10-13 ? Is it acidic or
basic?
4. The color of the flowers on a Hydrangea depends upon the pH of its soil.
If the soil is acidic, the flowers will be blue. If the soil is alkaline, the flowers
will be pink. If the soil shows a concentration of hydronium to be 6.3 x 10-5,
what is the pH level of the soil? Will the flowers be blue or pink?
All Rights Reserved © MathBits.com
5. The pH of your eyes is 7.2. Consequently, the ideal pH level in a swimming pool is 7.2. All pools
should be kept in the pH range between 7.0 and 7.6. If the pH level is too low, your eyes and nose
will burn, your swimwear will deteriorate, the water will not be well sanitized, and your skin will
become dry and itchy. If the pH level is too high, these same conditions will occur, in addition to
the water becoming cloudy. The pools listed below contain the indicated concentrations of
hydronium ions. Determine the pH level of each pool and state if it falls within the accepted range
stated here.
a) backyard pool: H 3O concentration = 2 10
-8
b) public outdoor pool: H 3O concentration = 7.9 10
-7
c ) private indoor pool: H 3O concentration = 6.31 10
-8
6. Maintaining a consistent pH level in an aquarium can be a daunting task. There simply is no
“normal” pH that applies to all types of fish. Saltwater fish prefer alkaline levels of 8.0 or higher,
while freshwater fish thrive in levels between 5.5 and 7.5. Listed below are the preferred pH levels
of some common freshwater fish. Determine the concentration of hydronium ions needed in the
water for an aquarium containing only that specific fish.
a) Goldfish 7.2
b) Angelfish 6.8
c) Siamese Fighting Fish 7.0
All Rights Reserved © MathBits.com