Chemical Synthesis

Lesson 2

Learning objective: To explain the reactions involving acids.

• Must: Describe the pH scale. Grade D• Must: Describe what happens during a

neutralisation reaction. Grade C• Should: Predict the name of products formed

during acid reactions. Grade B• Could: Write balanced symbol equations for the

acid reactions. Grade A

• Keywords: pH scale, salt, acid, word equation and balanced equation.

Let’s make a rainbow.

• Key skill used.• That you can read and

understand texts and take the appropriate action.

• As a team worker you can collaborate with others to work towards common goals.

pH scale.

• The pH scale tells us how acidic or alkaline a solution is. It is used to measure and help control the pH in a range of industries.

1. Indicators can be used to find out whether a solution is acid, alkaline or neutral

2. Universal Indicator can be used to find the pH of a solution

• Acid – red, pH less than 7• Neutral – green, pH = 7• Alkali – blue, pH greater than 7

pH scalepH scalepH scalepH scale

pH scale

pH scalepH scalepH scalepH scale

pH scale

pH scalepH scalepH scalepH scale

pH scale

Important acids.

• Hydrochloric acid – HCl(aq)

• Nitric acid– HNO3(aq)

• Sulfuric acid – H2SO4(aq)

• Make sure you learn and remember them!• What does the (aq) mean?

Acidic compounds in different states.

• Acids that are solids – citric and tartaric.• Acids that are liquids – nitric, sulfuric and

ethanoic.• Acids that are gases – hydrogen chloride.

Formula of some alkalis.

• Sodium hydroxide – NaOH• Potassium hydroxide – KOH• Magnesium hydroxide – Mg(OH)2

• Learn and remember these!

What is an acid?

• All acids contain hydrogen atoms.• When acids dissolve in water they produce

hydrogen ions, H+.• HCl(g) H+(aq) + Cl-(aq)

• That is why acids only behave like acids when they are dissolved in water.

What about alkalis?

• The same can be applied to alkalis.• This time it is the presence of the OH- ion that

makes a substance an alkali.• Strong alkalis like NaOH sodium hydroxide

split up completely.• NaOH(aq) Na+(aq) + OH-(aq)

What happens to the ions during neutralisation.

Ionic equations

• The reaction between acids and alkalis can be represented by the following equation:

• Acid and alkali

• H+(aq) + OH-

(aq) H2O(l)

• Note that water is produced.

Learning objective: To explain the reactions involving acids.

• Must: Describe the pH scale.• Must: Describe what happens during a

neutralisation reaction.• Should: Predict the name of products formed

during acid reactions.• Could: Write balanced symbol equations for the

acid reactions.

• Keywords: pH scale, salt, acid, word equation and balanced equation.

Neutralisation – Hydrochloric acidNeutralisation – Hydrochloric acidNeutralisation – Hydrochloric acidNeutralisation – Hydrochloric acid

Neutralisation

Neutralisation – Sulphuric acidNeutralisation – Sulphuric acidNeutralisation – Sulphuric acidNeutralisation – Sulphuric acid

Neutralisation

Neutralisation – Nitric acidNeutralisation – Nitric acidNeutralisation – Nitric acidNeutralisation – Nitric acid

Neutralisation

Discover - Monitoring Neutralisation.

• Follow the instructions for AC6.13.

• Add 5 cm3 of HCl up to 35cm3 and then 1cm3 up to 45cm3

• Record your results and plot the graph.

• Make sure you wear goggles.

• Key skills• Read and understand

texts and take appropriate action.

• Use appropriate mathematical procedures.

• Examine patterns and relationships.

• Team worker – collaborate with others to work towards common goals.

Strong acid/base titration.

This is the shapeof the curve when a strong acidis reacted with a strong base.

What do you noticeabout the shape?

Testing understanding.

• Click here for more examples of neutralisation reactions.

• Click here for more information and tests about acids and alkalis.

Learning objective: To explain the reactions involving acids.

• Must: Describe the pH scale.• Must: Describe what happens during a

neutralisation reaction.• Should: Predict the name of products formed

during acid reactions.• Could: Write balanced symbol equations for the

acid reactions.

• Keywords: pH scale, salt, acid, word equation and balanced equation.

Discover - Investigating acids.

• Follow the instructions for AC6.3.

• Record your results and write word equations for each reaction.

• Make sure you are wearing goggles.

• Key skills.• Read and understand

texts and take appropriate action.

• Team worker – collaborate with others to work towards common goals.

1.Acids react with alkaline solutions to form a salt and water

• Hydrochloric acid produces chlorides

• Nitric acid produces nitrates• Sulphuric acid produces

sulphates

Naming SaltsNaming SaltsNaming SaltsNaming Salts

Neutralisation

Reactions of metals with acidsReactions of metals with acids

Copy and complete the following reactions:

1) Calcium + hydrochloric acid

2) Zinc + hydrochloric acid

3) Iron + hydrochloric acid

4) Lithium + sulphuric acid

METAL + ACID SALT + HYDROGEN

e.g. magnesium + hydrochloric acid magnesium chloride + hydrogen

MgH Cl Mg

Cl

ClH

H

H Cl

Reactions of metal oxides with Reactions of metal oxides with acidacidA metal oxide is a compound containing a metal and oxide. They are

sometimes called BASES. For example:

Mg O NaNa

O

O

Al

AlO

O

Magnesium oxide

Sodium oxide Aluminium oxideMETAL OXIDE + ACID SALT + WATER

Copy and complete the following reactions:

1) Magnesium oxide + hydrochloric acid

2) Calcium oxide + hydrochloric acid

3) Sodium oxide + sulphuric acid

Mg OH Cl

Mg ClCl

HH OH Cl

Acid alkali reactionsAcid alkali reactionsA neutralisation reaction occurs when an acid reacts with an alkali. An alkali is a metal oxide or metal hydroxide dissolved in water.

ACID + ALKALI SALT + WATER

NaClH

H OH ClNa O

H

Copy and complete the following reactions:

1) Sodium hydroxide + hydrochloric acid

2) Calcium hydroxide + hydrochloric acid

3) Sodium hydroxide + sulphuric acid

4) Magnesium hydroxide + sulphuric acid

Reactions of metals carbonates with Reactions of metals carbonates with acidacid

A metal carbonate is a compound containing a metal, carbon and oxygen.

METAL CARBONATE + ACID SALT + CARBON DIOXIDE + WATER

Copy and complete the following reactions:

1) Magnesium carbonate + hydrochloric acid

2) Calcium carbonate + hydrochloric acid

3) Sodium carbonate + sulphuric acid

Mg H ClMg

Cl

Cl

HH

H Cl

C

O

O

OO

OO

C

Testing understanding.

• Click here for more word and symbol equations for reactions involving acids.

• Click here for revision notes and test on reactions involving acids.