Substances, Mixtures, and Solubility - McGraw-Hill Higher Education

Topic: Indicators
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links to information about the
types of pH indicators.
Activity Describe how plants
can act as indicators in acidic and
basic solutions.
Figure 20 The pH of a solution
is more acidic when greater
amounts of hydronium ions are
present.
Define what makes a pH 7 solution
neutral.
Indicators
What is a safe way to find out how acidic or basic a solution
is Indicators are compounds that react with acidic and basic
solutions and produce certain colors, depending on the solution’s
pH.
Because they are different colors at different pHs, indicators
can help you determine the pH of a solution. Some indicators,
such as litmus, are soaked into paper strips. When litmus paper
is placed in an acidic solution, it turns red. When placed in a
basic solution, litmus paper turns blue. Some indicators can
change through a wide range of colors, with each different color
appearing at a different pH value.
Neutralization
Perhaps you’ve heard someone complain about heartburn or
an upset stomach after eating spicy food. To feel better, the person
might have taken an antacid. Think about the word antacid
for a minute. How do antacids work
Heartburn or stomach discomfort is caused by excess
hydrochloric acid in the stomach. Hydrochloric acid helps break
down the food you eat, but too much of it can irritate your
stomach or digestive tract. An antacid product, often made from
the base magnesium hydroxide, Mg(OH) 2
, neutralizes the excess
acid. Neutralization (new truh luh ZAY shun) is the reaction of
an acid with a base. It is called this because the properties of
both the acid and base are diminished, or neutralized. In most
cases, the reaction produces a water and a salt. Figure 20 illustrates
the relative amounts of hydronium and hydroxide ions
between pH 0 and pH 14.
What are the products of neutralization
pH 0 7
14
238 CHAPTER 8 Substances, Mixtures, and Solubility