© boardworks ltd 20111 of 18. © boardworks ltd 20112 of 18 acids and alkalis how many examples of...


Acids and alkalis

How many examples of acids and alkalis can you spot?


Acids: true or false?


Alkalis: true or false?


Mixing an acid and an alkali

What happens when an acid and an alkali are mixed?

Mixing an acid and an alkali causes a chemical reaction.

How could you check that a chemical reaction has taken place?

+

acid alkali


Mixing acids and alkalis


What is neutralization?

The chemical reaction between an acid and an alkali is called neutralization.

What is the pH value of the mixture of salt and water?

The chemical reaction between an acid and an alkali can be written as:

+ acid alkali salt + water

+

acid alkali salt + water

The mixture of salt and water is neutral, so its pH is 7.


Neutralizing stings

Bee stings are acidic.

Which safe household substances could you use to treat a bee sting?

Wasp stings are alkaline.

Which safe household substances could you use to treat a wasp sting?


Separating a salt


Making salts

The salt produced by a neutralization reaction depends on the acid and the alkali used.

Sodium chloride is produced by the reaction between hydrochloric acid and sodium hydroxide.

Which acid and which alkali would be needed to make the salt potassium chloride?

potassium hydroxide

hydrochloric acid +

potassium chloride

water+

+ +sodium

hydroxidesodium chloride

hydrochloric acid

water


Naming salts

When an alkali reacts with hydrochloric acid, the salt produced is a chloride.

When an alkali reacts with sulfuric acid, the salt produced is a sulfate.

When an alkali reacts with nitric acid, the salt produced is a nitrate.

Which acid would be needed to make these salts?

1. copper nitrate

2. magnesium chloride

3. sodium sulfate


Making salts: word equations

potassium hydroxide

hydrochloric acid +

potassium chloride

water+

sodium hydroxide

sulfuric acid + sodium sulfate

water+

potassium hydroxide

nitric acid + potassium

nitratewater+

Complete these word equations:


Making salts: completing equations


Making salts: symbol equations

potassium hydroxide

potassium chloride

hydrochloric acid

water+ +

HCl KOH KCl H2O+ +

Complete these symbol equations:

magnesium hydroxide

magnesium sulfate

sulfuric acid water+ +

+H2SO4 Mg(OH)2 Na2SO4 2H2O +

potassium hydroxide

potassiumnitrate

nitric acid water+ +

HNO3 KOH KNO3 H2O+ +


Balancing equations

The balanced symbol equation for a chemical reaction shows the ratio of reactants and products involved. For example:

When a chemical reaction occurs, it can be described by a a symbol equation.

+

sodium hydroxide

sodium sulfate

sulfuric acid water+ +

H2SO4 2NaOH Na2SO4 2H2O +

An ‘unbalanced’ equation can be balanced by multiplying the different atoms and molecules on each side by different amounts, so that they match.


Balancing equations

If you count the number of atoms of each type on each side of this equation, you will see that they do not match.

So, multiply the sodium atoms on the left by 2:

Now that the number of sodium atoms on each side is equal the number of hydrogen atoms on the left side has increased. So multiply the number of hydrogen atoms on the right by 2.

+H2SO4 NaOH Na2SO4 H2O +

+H2SO4 2NaOH Na2SO4 H2O +

+H2SO4 2NaOH Na2SO4 2H2O +


Balancing equations for making salts


Indigestion remedies

Indigestion and heartburn are caused by an excess of acid in your stomach.

Indigestion remedies such as Milk of Magnesia contain antacids, like magnesium oxide and calcium carbonate.

What do you think antacids do to the acid in your stomach?

The acid in your stomach that helps you break down your food is called hydrochloric acid. It has a pH of between 1 and 2.

© boardworks ltd 20111 of 18. © boardworks ltd 20112 of 18 acids and alkalis how many examples of...

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