reactions of acids


• Write an equation for a neutralisation reaction.

• State the difference between an alkali and a base


Metal oxide

Metal oxides are compounds made from a metal and oxygen.

For example, burning magnesium in oxygen produces magnesium oxide.

magnesium magnesium oxideoxygen+ �

Acids react with metal oxides to make a salt and water.

For example, sulfuric acid reacts with copper oxide to make copper sulfate and water.

copper oxide

copper sulfate

sulfuric acid water+ � +


Base or alkali?

Bases are substances that react with acids, which include metals oxides, hydroxides and carbonates.

Alkalis are substances that react with acids and which are soluble in water.

Copper oxide is a base, but not an alkali, because it reacts with acids, but does not dissolve in water.

Sodium hydroxide is an alkali (and a base), because it reacts with acids and it is soluble in water.

bases: react with acids

alkalis: soluble in

water


Acids and metal oxides


Making copper sulfate


Metal oxides + acids


What is the formula?


Formulae

How do we know that the formula of sodium chloride is NaCl, while the formula of copper chloride is CuCl2?

It is because of the combining power of the atoms.

Sodium has a combining power of 1, so it bonds with one other atom.

Chlorine also has a combining power of 1, so it bonds with one other atom.

Copper, though, has a combining power of 2, so it needs to bond to two chlorine atoms.

The formula of magnesium chloride is MgCl2, so what do you think is the combining power of magnesium?


Formulae and combining powers

Here are the combining powers of some metal and non-metal atoms:

1

1

2

2

Na

K

Mg

Cu

metal atomcombining

powernon-metal

atomcombining

power

Cl

F

O

N

1

1

2

3


Formulae and combining powers


Acid and carbonate

When a carbonate reacts with an acid, it gives off carbon dioxide gas.

How could you test the gas given off, to confirm that it is carbon dioxide?

What would you observe in this test?

carbon dioxide

limewater


Acid and carbonate

Calcium carbonate is a substance that is naturally found in the shells of sea creatures and snails.

What salt do you think will be produced by the reaction of hydrochloric acid and calcium carbonate?

calcium carbonate

calcium chloride

hydrochloric acid

water+ � +carbon dioxide+

The products of the reaction between a carbonate and an acid are a salt, carbon dioxide and water.


Reaction of carbonates


Acid and metal

Acids also react with metals to make a gas.

When an acid reacts with a metal, the gas produced makes a lighted splint go pop.

What is this gas?

A salt is also produced during the reaction. What is the name of the salt that will be produced by the reaction of hydrochloric acid with calcium?

calciumcalcium chloride

hydrochloric acid + � hydrogen+


Choose your reaction

Some metals react violently with acids, so it wouldn’t be safe to use them to make a salt in the classroom.

However, if you still wanted to make that salt, you could use the metal carbonate instead.

Sodium reacts very violently with sulfuric acid, so should not be uses to make sodium sulfate. However, you could safely use sodium carbonate.

Could you safely use sodium hydroxide to make sodium sulfate? What about sodium oxide?

sodium carbonate

sodium sulfate

sulfuricacid + �

carbon dioxide+ water+


Choose your reaction


What is acid rain?

Rainwater has a pH of about 5.6, which means that it is naturally slightly acidic.

Rainwater with a lower pH than normal is called acid rain.

Burning of fossil fuels in power stations and cars forms pollutants such as sulfur dioxide and nitrogen oxides.

Why is acid rain a serious environmental problem?

These gases dissolve in rainwater to make sulfuric acid and nitric acid, which are strong acids, so also form acid rain.

This natural acidity is due to carbon dioxide in the air dissolving into the rain, forming a weak acid called carbonic acid.


How does acid rain work?


Effects of acid rain

Acid rain has many damaging effects on the environment:

The acids in acid rain speed up the chemical weathering of rocks and buildings.

What can be done to reduce acid rain and its effects?

Soil that becomes more acidic has fewer nutrients so trees and other plants cannot grow. Acid rain also damages trees by breaking down the waxy coating of leaves.

Rivers, lakes and streams become more acidic so that animals and plants cannot live in them.


Reducing acid rain

Governments are working to reduce the emissions of the acidic pollutants produced by burning fossil fuels.

Sulfur dioxide is formed when coal containing sulfur is burned in power stations. This acidic pollutant can be removed from the gases before they are released into the atmosphere.

How do these changes help to reduce acid rain?

Nitrogen oxides are formed when petrol burns in a car’s engine. Exhaust systems can be fitted with a catalytic converter which turns harmful gases into harmless gases.


Acid rain – a global problem

Forests in Scandinavian countries such as Sweden have suffered greatly from the damaging effects of acid rain.

However, scientists have shown that the acid rain that falls in Sweden is not produced there. The source of the acidic pollutants is in fact more likely to be UK factories and power stations.

Is it right that a country can directly cause pollution in another?

This happens because air pollution can be carried high up into the sky, where it is pushed by strong winds towards other countries.


Should pollution be contained?


Limiting the effects of acid rain: opinions


Glossary


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Multiple-choice quiz

reactions of acids

Science

base boardworks

metal oxides boardworks

powers boardworks

mnttempunoconv2014 boardworks

copper sulfate boardworks

reaction of hydrochloric

combining power of magnesium

combining powers