6.2 - The pH Scale and Indicators
The ______________ is a numerical scale, ranging from _____________, that is used to classify solutions as
_________________, __________________, or _____________________.
The pHs of a variety of solutions (pool water, foods and beverages, and solutions from industrial processes)
are regularly monitored.
Acidic: ___________
Basic: _______________
Neutral: ______________
A pH (__________________________) value relates to the _____________________________________ in
a solution. Values __________________ or _________________ exponentially (by a _________________)
as you move up or down the scale.
Determining the pH of a Solution
____________________________ are substances that change colour to show the concentration of hydrogen
ions (_______) and hydroxide ions (________) in a solution.
______________________ have a sensor or probe that electronically produces a ______________________
(real time) reading of the pH of a solution that is displayed digitally on the meter.
______________________________________________________ – chemically treated indicator paper.
Acids _________ Blue ______________ Red. Bases _________ Red _______________ Blue. This simple
indicator can determine whether a solution is acidic, basic, or neutral.
_________________________ and ________________ are composed of a mixture of indicators that change
to different colours under different pH conditions. These indicators cover the ________ pH range from 0-14.
Other pH Indicators
1
pH Indicators in Nature - A variety of plants contain juices that can act as natural acid-base indicators. A
few of these are listed below.
Acids and Bases: Similarities and Differences
2
6.3 - Reactions of Acids and Bases
__________________________ is the reaction of an acid and a base to form a ________ and ___________.
___________(aq) + _____________(aq) 
____________(l) + ____________(aq)
Neutralizing Stomach Acid
________________ such as those shown below (e.g.
tums) are taken to ________________ excess acid
produced in the dark pits of the ____________ lining
shown on the right. This excess acid leads to a
_______________ sensation called ______________.
Neutralizing Acid Spills
The environmental damage caused by accidental acid spills like the one from the train derailment shown
below can be reduced by __________________________________________________________________
________________ (aq) + ________________(aq)  _______________(aq) + ______________ (l)
Acid Precipitation
_____________________________ (a.k.a. _________________) is rain that has a pH lower than that of
normal rain (which is around ________________).
Acid precipitation is primarily caused by emissions of ___________________ and ____________________
that combine with _________ and other gases in the atmosphere to produce _________ and _____________
Sulfure oxide emissions: __________ (g) + __________(l)  _____________ (aq)
Nitrogen oxide emissions: __________ (g) + __________(l)  _____________ (aq)
Effects of Acid Precipitation
Changes in the pH of water can be __________________ when a rapid snowmelt in the spring releases
__________________amounts of acid __________________________________.
____________ changes in the pH of waterways can reduce _________ and ________________ populations
dramatically. Food that these animals rely on _________________, and low pH levels have a
___________________ effect on ________________________.
Renewing Acidified Lakes
One strategy for reversing the effects of acid precipitation is to _________________________________ to
neutralize the acid in lakes. _____________________________ involves the application of basic materials,
typically __________________________, to renew acidified lakes and regions.
Homework
Read Pages 229-235 and Answer Q’s 1-4 on Page 235 and Read Pages 236-246 and do Q`s 1,2,4
3
DATE:
NAME:
CHAPTER 6
Section 6.2 Review
(Alternative Format)
CLASS:
BLM 6-8
1. What is the general pattern in chemical formulas that allows one to determine if a substance is an acid or
a base? Provide examples.
_________________________________________________________________________________
_________________________________________________________________________________
2. What is a pH scale and what is the main purpose for its use?
_________________________________________________________________________________
_________________________________________________________________________________
3. What does pH stand for?
_________________________________________________________________________________
4. Draw a pH scale and place these substances on the scale:
baking soda
human blood
battery acid
Milk of Magnesia®
bleach
tomatoes
drain cleaner
vinegar
gastric juice
water
5.
Fill in the blanks.
a. __________ substances have a pH of less than 7.
b. __________ substances have a pH of 7.
c. __________ substances have a pH of more than 7.
6. A solution has a pH of 5. Explain how the number of hydroxide ions in the solution compares to the
number of hydrogen ions.
_________________________________________________________________________________
_________________________________________________________________________________
4
7. How much more acidic is a solution with a pH of 4.5 than a solution with a pH of 6.5? Explain.
_________________________________________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
8. What is an indicator? List different types of indicators: 3 natural and 3 chemical.
_________________________________________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
9. How does a universal indicator differ from other types of indicators?
_________________________________________________________________________________
_________________________________________________________________________________
10. Use a Venn diagram to compare the properties of acids and bases.
Section 6.3 Review
(Alternative Format)
Use the words below to complete questions 1 through 10. You can use words more than once.
salt
metals
neutralization
nitric acid
ores
increasing
limestone
OH–
water
destroyed
lowered
H2O
tailing
magnesium
hydroxide
pH
H2SO4
precipitation
antacids
non-metal oxides heartburn
neutralize
bases
sulfur dioxide
1
double
displacement
AB
gastric
BC
digestion
NO2
hydrogen ions
H+
acidic
hydrochloric
acid
1. An acid reacts with a base to produce ______________________ and ________________________.
2. This type of reaction is called ______________________________.
3. In the reaction (H+) _________________ _________________ combine with (____) hydroxide ions
to form (HOH or _________________) water molecules. ________ + OH- → H2O
4. The word neutralization is used because the acid and base properties of H+ and OH- are
_________________ or neutralized.
5
5. Neutralization is a type of ___________________ ___________________ reaction where
_____ + CD → AD + ______.
6. Neutralization can also occur in the body. Your stomach contains a solution of _________________
_________________ called _________________ juice that has a pH of about _________________.
7. The gastric juice is important to break down food particles during the process of _________________.
Too much acid may damage the lining of the stomach and cause pain.
A common treatment for _________________ is the use of _________________. They are designed
to _________________ the acid because they are _________________ containing (Mg(OH)2)
_________________ _________________ and (Al(OH)3) aluminum hydroxide.
8. Acid _________________ forms when _________________ such as nitrogen dioxide
(_________________) and _________________ _________________ (SO2) dissolve in water. This
reaction creates _________________ solutions such as ________________ _________________
(HNO3) and sulfuric acid (_________________).
9. Acid precipitation damages rivers and lakes because the _________________ of the water source is
_________________. Lakes may be renewed by adding _________________ to _________________
the pH of the water. This process helps to _________________ the acid and raise the pH.
10. Acids are used in industry for extracting _________________ such as copper, gold, and nickel from
_________________. This process sometimes causes contamination of the _________________
materials.
11. Explain if it is reasonable for a chemist to use the following reaction to produce solid silver.
K(s) + Ag(NO3)(aq)
_________________________________________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
6