Acids and Alkalis

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Transcript Acids and Alkalis

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Acids and Alkalis

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What are acids and alkalis?

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What are bases?

All alkalis are

bases

. Bases are substances that react with acids by absorbing hydrogen ions (

H +

The oxides, hydroxides and carbonates of metals, such as sodium hydroxide, are bases.

Some bases are soluble in water. These are called

alkalis

All alkalis contain hydroxide ions (

OH –

). The more

OH –

ions in the solution, the stronger the alkali.

What are indicators?

Indicators

are chemicals that change colour in the presence of an acid or an alkali.

There are many different indicators. Lots of them come from plants, like red cabbage. Different indicators turn different colours. Geranium plants grown in acidic soil have red flowers, while geraniums grown in alkali soil have blue flowers.

Universal indicator

is a mixture of indicators. It is useful because it shows a range of colours from pH 1 –14.

What does the pH scale show?

The pH scale runs from 1 to 14. The numbers 1 to 6 represent acidic conditions and 8 to 14 represent alkali conditions. A pH value 7 is neutral. What are the pH values of some everyday items?

1 2 3 4 5 6 7 8 9 10 11 12 13 14

What does the pH scale show?

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What is the order of pH?

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Acids and bases – true or false?

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Making salts

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pH change during neutralization

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How are salts made and named?

When an acid reacts with a base, a

neutralization

reaction occurs and produces a chemical called a

salt

acid + base



salt + water

The name of the salt depends on the names of the reactants.

 The

first part

of the salt’s name comes from the metal in the

base

:  The

second part

of the salt’s name comes from the

acid

: e.g. sulfuric acid …sulfate For example, if sodium hydroxide neutralizes sulfuric acid, the product is a salt called sodium sulfate.

Naming salts

Making salts with an acid and an alkali

When an acid reacts with an alkali,

H +

and

OH -

ions from the acid ions from the alkali combine to produce a salt and water.

Water is formed because the oxygen and hydrogen from the alkali react with the hydrogen from the acid to produce molecules of water (H 2 O).

For example:

hydrochloric acid + sodium hydroxide H Cl

(aq) 

sodium chloride + + Na OH

(aq) 

NaCl

(aq)

+ water H 2 O

Glossary

Multiple-choice quiz