Acids, Bases and salts

Acids and Bases

What are the
properties of acids
and alkalis?
What is
neutralisation?
What are
indicators?

Acids
Acids form acidic solutions in
water. Acids produce hydrogen
ions, H+ in aqueous solution. For
example:

HCl(aq) → H+(aq) + Cl-(aq)

Acidic solutions have pH values less
than 7.

Alkalis
Alkalis form alkaline solutions in
water. Alkalis produce hydroxide
ions, OH- in aqueous solution. For
example:

NaOH(aq) → Na+(aq) + OH-(aq)

Alkaline solutions have pH values
greater than 7.

Multiple Choice

Which of the following word pairs correctly completes the sentence below?
_______ are corrosive substances characterized as having a strong smell, a sour taste, and a _______.

• Acids; pH less than 7

• Acids; pH greater than 7

• Bases; pH greater than 7

• Bases; pH less than 7

Multiple Choice

Which of the following is a base?

• orange juice

• water

• vinegar

• dishwashing detergent

Multiple Choice

 Which of the following is an acid?

• shampoo

• baking soda

• orange juice

• water

Multiple Choice

 Which of the following is an acid?

• shampoo

• baking soda

• orange juice

• water

Multiple Choice

Which type of ion does a base produce when it is dissolved in water?

• oxide

• oxygen

• hydrogen

• hydroxide

Multiple Choice

Which of the following is true about acids and bases?

• The lower the pH, the stronger the acid

• the higher the pH, the stronger the acid

• The lower the pH, the more neutral the acid

• The higher the pH, the weaker the base

Multiple Choice

On the pH scale what numbers are bases?

• 8-14

• 0-7

• 7

• 1

Multiple Choice

On the pH scale what numbers are acids?

• 8-14

• 0-7

• 7

• 1

Multiple Choice

Which of the following word pairs correctly completes the sentence below?

_______ are corrosive substances characterized as having a oily feel, a bitter taste, and a _______.

• Acids; pH less than 7

• Acids; pH greater than 7

• Bases; pH greater than 7

• Bases; pH less than 7

Multiple Choice

Which type of ion does an acid produce when it is dissolved in water?

• oxide

• oxygen

• hydronium

• hydroxide

Neutral solutions
A neutral solution is neither acidic,
nor alkaline. A neutral solution has
a pH value of 7.

Indicators and the pH scale
The pH scale measures the acidity
or alkalinity of a solution. The pH
of a solution can be measured
using a pH probe, or estimated
using universal indicator and a
colour chart.

Universal indicator is one
example of an acid-alkali
indicator. Indicators show
whether a solution is acidic,
neutral (pH 7) or alkaline.

Multiple Choice

If an acid is combined with a base of equal strength, the result will most likely be

• a neutral solution.

• a stronger acid.

• impossible to tell without testing the pH.

• a stronger base

Multiple Choice

Pure water has a pH of 7. Pure water _______.

• is a base

• is a neutral substance

• could be either an acid or a base

• is an acid

Multiple Choice

Explain what happens when a strong acid and a strong base are poured into the same container.

• they form separate layers

• they mix physically but not chemically

• they break apart into separate elements

• they react chemically to form a salt

Multiple Choice

On the pH scale what numbers are neutrals?

• 8-14

• 0-7

• 7

• 1

Multiple Choice

When an equal strength acid and base are mixed, what kind of chemical reaction occurs?

• Neutralization

• Combustion

• Oxdation

• Decomposition

Indicators are used to determine whether a solution is acidic or
alkaline. Acids react with metals, bases and carbonates to produce
salts. Neutralisation is the reaction between an acid and a base.

Neutralisation
Bases and alkalis
A base is any substance that reacts with an acid to form a salt and
water only. This means that metal oxides and metal hydroxides are
bases.

Bases that are soluble in water are called alkalis and they dissolve in
water to form alkaline solutions. For example:
copper oxide is a base, but it is not an alkali because it is insoluble
in water. Sodium hydroxide is a base, and it dissolves in water so it is
also an alkali.

A neutralisation reaction is a reaction between an acid and a base.
Remember:
•acids in solution are sources of hydrogen ions, H+
•alkalis in solution are sources of hydroxide ions, OH-
In acid-alkali neutralisation reactions, hydrogen ions from the acid react with
hydroxide ions from the alkali:
H+(aq) + OH-(aq) → H2O(l)

Multiple Choice

What would be the best way to determine if a substance is an acid or a base?

• Drop some on your skin.

• Taste it.

• Use an indicator such as litmus or universal indicator.

• Add it to some metal and test any gas that evolves.

Multiple Choice

If a student tested a solution with blue litmus paper and it remained blue, what does this mean?

• The litmus paper is old, they should open a new pack and try again.

• The solution is neutral.

• The solution is an acid.

• The solution is a base.

• Need to test with red litmus for confirm that the solution is a base

Multiple Choice

Which of the following statements about litmus and universal indicator are true?

• Universal indicator can determine the strength of an acid or base, whereas litmus cannot.

• Litmus gives qualitative data while universal indicator provides quantitative data.

• Both litmus and universal indicator test solutions not solids.

• All these statements are correct.

Multiple Choice

What color would you expect an acidic solution to turn if universal indicator was added to it?

• Yellow

• Dark Green

• Blue

• Violet

Multiple Choice

What color would you expect basic solution to turn if universal indicator was added to it?

• Green

• Violet

• Red

• Yellow

Multiple Select

Which solution can turn phenolphthalein pink?

• Sodium hydroxide

• Vinegar

• Tomato

• Hydrochloric acid

Multiple Select

Which solution can turn phenolphthalein pink?

• Sodium hydroxide

• Vinegar

• Tomato

• Hydrochloric acid

Multiple Select

Which solution can turn phenolphthalein pink?

• Sodium hydroxide

• Vinegar

• Tomato

• Hydrochloric acid

Multiple Select

Which solution would turn litmus red?

• Potassium hydroxide

• Sodium chloride

• HNO₃

• Ammonia

Multiple Select

Which solution would turn litmus blue?

• HCl

• Citric fruits

• H₂SO₃

• NH₃

Multiple Select

What is the nature of the solution present in the beaker?

• Alkali

• Acidic

• Neutral

• Water

Multiple Select

Which of the set of pH paper depicts that the dipped solution is highly acidic?

(compare with the pH scale and find out)

Multiple Choice

Which solution can turn phenolphthalein pink?

• NaOH_(aq)

• CH₃COOH_(aq)

• CH₂OH_(aq)

• HCl_(aq)

Multiple Choice

Household vinegar has a pH of approximately 3.0. Which would appear yellow when added to a vinegar solution?

• Methyl orange

• Bromcresol green

• Phenophthalein

• Litmus

Multiple Choice

Which solution would turn litmus red?

• KOH_(aq)

• NaCl_(aq)

• HCl_(aq)

• NH_3(aq)

Multiple Choice

Which solution would turn litmus blue?

• HCl_(aq)

• CH₃COOH_(aq)

• H₂SO_3(aq)

• NH_3(aq)

Multiple Choice

Phenolphthalein has a pink color in a solution that has a pH of

• 5

• 11

• 1

• 7

Multiple Choice

Which indicators would cause a solution with a pH of 2 to turn red?

• Bromthymol blue and thymol blue

• Bromcresol green and litmus

• Litmus and methyl orange

• Methyl orange and phenolphthalein

Multiple Choice

An indicator was used to test a water solution with a pH of 3. Which indicator color would be observed?

• Yellow with methyl orange

• Pink with phenolphthalein

• Blue with litmus

• Yellow with bromcresol green

Multiple Choice

To neutralize a solution of HCl_(aq), what solution should be added?

• NaOH_(aq)

• H₃PO_4(aq)

• HNO_3(aq)

• C₁₂H₂₂O_11(aq)

Multiple Choice

Which of the following colors are false with a solution with a pH of 9?

• Litmus will beblue

• Bromthymol blue will be yellow

• Bromcresol green will be blue

• Phenolphthalein will be colorless