Acids Bases & Salts (Acids)

an e-learning series by ycs

Learning Objectives

• By the end of the lesson, pupils would be able to– Define the meaning of acids– Name common acids– Explain the importance of water as solvent– Describe the physical properties of acids– Describe the chemical reaction of acids– Explain the basicity of acids

Types of Acids

• Mineral acids– hydrochloric acid,

HCl

– nitric acid, HNO3

– sulphuric acid, H2SO4

• Organic acids– ethanoic acid

(vinegar), CH3COOH

Definition

• A substance when dissolved in water

produces hydrogen ions as the only positive ions

HCl (aq) H+ (aq) + Cl- (aq)

H+ ion

click icon

Releasing the H+ ions

• Water is needed for the release of H+ ions and not organic solvent.

– e.g. If the gas hydrogen chloride, HCl(g), is dissolved in methylbenzene, no H+ ions would be produced.

What does the H+ do?

• The hydrogen ion is responsible for the properties and chemical reactions of acids.

• What are some properties and chemical reactions of acids?

Properties of Acids

• Sour taste

• Turns blue litmus red

• Changes the colour of indicators like universal indicator, methyl orange..etc

Indicators & pH Scale

• Click on the pH Scale below to learn more about indicators and the pH.

The pH Scale

Chemical Reactions

• Acids react with metals to form salt and hydrogen gas.

Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g)

Fe(s) + 2HNO3(aq) Fe(NO3)2(aq) + H2(g)

Ca(s) + H2SO4(aq) CaSO4(aq) + H2(g)

• Acids react with carbonates to form salt, water and carbon dioxide gas.

CaCO3(s) + 2HCl(aq)

CaCl2(aq) + H2O(l) + CO2(g)

Na2CO3(s) + H2SO4(aq)

Na2SO4(aq) + H2O(l) + CO2(g)

Chemical Reactions

• Acids react with bases to form salt and water.

NaOH(aq) + HNO3(aq) NaNO3(aq) + H2O(l)

CuO(s) + 2HCl(aq) CuCl2(aq) + H2O(l)

• This reaction is known as neutralisation and is represented by the ionic equation,– H+ (aq) + OH- (aq) H2O (l)

Chemical Reactions

• If an acid contains one replaceable hydrogen, it is a monobasic acid

• What can you say about dibasic and tribasic?

• Determine the basicity of these acids,– HCl– H2SO4

– H3PO4

Basicity of Acids

• Write the chemical equations for the following reaction

calcium + dilute hydrochloric acid Iron(II) carbonate + dilute nitric acidmagnesium oxide + dilute sulphuric acid

Nutshell Activity

• Hydrogen chloride was bubbled into an organic solvent, methylbenzene. The resulting solution has no effect on litmus paper. Explain this observation.

Nutshell Activity

• Acids contain replaceable hydrogen. For each hydrogen replaced by a positive ion, a salt is produced. How many types of salts can be produced from a dibasic acid?

• Give an example of a monobasic, dibasic and tribasic acid.

Nutshell Activity

• To learn more about the topic on acids you can follow this link here to Chinese High School Chemistry VLE’s webpage.

Extension