ACIDS(LESSON 1)

Acids and bases

What’s your favorite drink?

Food for thought

What causes the erosion of the tooth?What is the reason behind this phenomenon?

Lesson objectives

Define acid in terms of ions produced in aqueous solution.

State and describe the chemical properties of acids.

State the physical properties of acids.Recognize and understand the use of litmus

paper and universal indicators.

Acids in action!

Common Acids Chemical Formula

Uses

Sulfuric acid H2SO4 Make detergent, fertilisers and soaps.Used in car batteries.

Hydrochloric acid HCl Remove rust from body of a car before painting.

Nitric acid HNO3 Make fertilisers

Ethanoic Acid (Vinegar)

CH3COOH Preserve vegetables.

Citric Acid C6H8O7 Found in fruits- orange and lemon.

When water is added into acid…

Sulfuric acidH2SO4 (aq) 2H+ (aq) + SO4

2-(aq)

Hydrochloric acidHCl (aq) H+ (aq) + Cl-(aq)

What do you notice about these two

equations?

What do you notice about these two

equations?

1 minute to think and discuss with your partner.

Hint: Three points to note. Focus on the product and the state symbols.

Sulfuric acidH2SO4 (aq) 2H+ (aq) + SO4

2-(aq)

Hydrochloric acidHCl (aq) H+ (aq) + Cl-(aq)

In both equations, 1. An anion and a cation is produced. 2. Cation is H+ 3. The acid and ions formed are in

aqueous state.

In both equations, 1. An anion and a cation is produced. 2. Cation is H+ 3. The acid and ions formed are in

aqueous state.

Sulfuric acidH2SO4 (aq) 2H+ (aq) + SO4

2-(aq)

Hydrochloric acidHCl (aq) H+ (aq) + Cl-(aq)

Dissociation/ Ionization of acids. i.e. Acid is being ionized in water to form H+ ions and SO4

2- ions.

Definition of an acid

An acid is a substance that produces hydrogen ions, H+(aq), when dissolved in water.

ExampleHNO3(aq) H+(aq) + NO3

-(aq)Role of water in acidic propertiesAcids only display the properties of acids when they are dissolved in water. Acids dissociate in water to produce H+ ions which are responsible for the acidic properties.

Nitric Acid

Chemical properties of acids

Acids can take part in the following reactions:

1.Acids + metals 2.Acids + metal carbonates3.Acids + bases (Metal oxides / Metal hydroxides)

Acid + metals

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

General word equationmetal + acid salt + hydrogen

Mg(s) + H2SO4(aq) MgSO4(aq) +H2(g)

Note:A salt is a compound obtained when the hydrogen of an acid is replaced by a metal or an ammonium ion, NH4

+

Salt of sulfuric acid sulfates

Salt of nitric acid nitrates

Salt of hydrochloric acid chlorides

magnesium

Dilute sulfuric acid Magnesium sulfateHydrogen

Acid + metal carbonates

Acid reacts with metal carbonates to form salt, carbon dioxide and water.

General word equation:

acid + metal carbonate salt + water + carbon dioxide

Example:Na2CO3(s) + 2HCl(aq) 2NaCl(aq) + H2O(l) +CO2(g) Sodium carbonate

Dilute hydrochloric acid

Sodium chloride

Water Carbon dioxide

Acid + bases

Acid reacts with bases (metal oxide or metal hydroxide) to form salt and water only. This reaction is known as neutralisation.

General word equation:Acid + metal oxide/ metal hydroxide salt + water

Example:

ZnO(s) + H2SO4(aq) ZnSO4(aq) + H2O(l)Zinc oxide

Dilute sulfuric acid

Zinc sulfate

Water

Physical Properties of Acid

Acids have sour taste.

In acids, the free moving ions are able to conduct electricity.

Physical Properties of Acid

Acids are corrosive.

Physical Properties of Acid

Acids turn damp blue litmus paper red.

Acids have pH values of less than 7.

What have we learnt today?

What are acids?Examples of common acids and their uses.The chemical properties of acidsThe physical properties of acids

Mini Checkpoint

Write the chemical equations for the following reactions:

1.Magnesium and hydrochloric acid2.Zinc oxide and nitric acid3.Calcium carbonate and nitric acid