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Acidic, Basic and Neutral Solutions


Acidic, Basic and Neutral Solutions Chapter 9, Lesson 2 Acids An acid is a substance that releases a positively charged hydrogen ion, H+, in water. – PowerPoint PPT presentation

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Title: Acidic, Basic and Neutral Solutions

Acidic, Basic and Neutral Solutions
  • Chapter 9, Lesson 2

  • An acid is a substance that releases a positively
    charged hydrogen ion, H, in water.
  • Acids taste sour and turn blue litmus paper red.
  • The hydrogen ion from an acid combines with a
    water molecule in solution to form a hydronium
    ion, which has the formula H3O
  • Because acid solutions contain ions, they conduct

Hydronium ion
  • When an acid dissolves, it releases a hydrogen
  • The H ion combines with water to form H3O, the
    positively charged hydronium ion.

What is a hydronium ion?
Uses of Acids
  • Acids are important in several body processes,
    including breaking down food in the stomach.
  • Acids are also used in making many products, such
    as fertilizers, detergent, and cleaners.

  • A base is a substance that produces hydroxide
    ions when dissolved in water.
  • The formula for the hydroxide ion is OH-
  • Bases feel slippery on your skin, taste bitter,
    and turn red litmus paper blue.
  • Most bases are ionic compounds.

Hydroxide ion
  • In water, bases separate into a positive ion and
    the hydroxide ion (OH).
  • All the properties of bases are a result of the
    presence of hydroxide ions that form when the
    base is dissolved in water.

Uses of Bases
  • Common bases include baking soda and cleaning
  • Bases are also used to produce new products, such
    as soap, paper, and plaster.

Acids and Bases
What is pH?
  • pH is a numerical scale used to indicate how
    acidic or basic a solution is.
  • The pH scale runs from 0 to 14.
  • Acids are below 7 strong acids are near 0.
  • Bases are above 7 strong bases near 14.
  • Neutral solutions have a pH of 7.

pH and Hydronium ion Concentration
  • The higher the concentration of hydronium ions,
    the more acidic a solution is.
  • All acid and base solutions contain both
    hydronium ions and hydroxide ions.
  • In a neutral solution (pH7) the hydronium and
    hydroxide ion concentrations are equal.
  • A change in one pH unit represents a tenfold
    change in the acidity or alkalinity (how basic)
    of a solution.

(No Transcript)
  • When an acid and a base are mixed, a
    neutralization reaction occurs.
  • A neutralization reaction produces water and a
  • Stomach acid reacts with magnesium hydroxide in
    the following equation
  • 2HCl Mg(OH)2 ? MgCl2 2H2O
  • Neither of the products is acidic or basic.

How is pH measured?
  • An indicator is a compound that changes form one
    color to another within a particular pH range.
  • Indicators can be used to determine approximate
    pH, simply whether something is acidic or basic.

How is pH measured?
pH strips
  • Litmus is one of the simplest indicator test
    papers but also the least accurate.
  • pH testing strips are a quick way of determining
    the approximate pH of a solution.

pH Meters
  • pH meters are electronic instruments with an
    electrode that is sensitive to hydronium ions
    present in a solution.
  • Accurately measures pH
  • Requires an electric source to operate

pH Meters (contd)
Lesson Review 9-2
  • 1. An acid with a pH of 3 is contains how many
    times as many hydronium ions as an acid with a pH
    of 6?
  • A 1000
  • B 3
  • C 30
  • D 100

Lesson Review 9-2
  • 2. When an acid and base are mixed, the products
    are ____ and ____.
  • A water a base
  • B water ammonia
  • C water salt
  • D ammonia salt

Lesson Review 9-2
  • 3. Red litmus paper is dipped in a solution. The
    paper turns blue. The solution must have been
  • A acidic
  • B homogeneous
  • C basic
  • D polar

Lesson Review 9-2
  • 4. Blue litmus paper turns ____ in acid
  • A red
  • B orange
  • C green
  • D blue

Lesson Review 9-2
  • 5. Which of the following is a hydroxide ion?
  • A H3O
  • B H
  • C OH
  • D NH4

Lesson Review 9-2
  • 6. Which is a property of a base?
  • A sour taste
  • B produces OH in water
  • C produces H in water
  • D reacts with metal to produce hydrogen gas

Lesson Review 9-2
  • 7. What ions are present in the greatest amount
    in a solution with a pH of 2.5?
  • A hydroxide
  • B hydrogen
  • C hydronium
  • D oxygen

Lesson Review 9-2
  • 8. What is the symbol for the hydrogen ion?
  • A H3O
  • B H2O
  • C H
  • D OH