Acids and bases Acids (Lesson 1)

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 acid H2SO4 (aq) 2H+ (aq) + SO42-(aq) Hydrochloric acid HCl (aq)  H+ (aq) + Cl-(aq) What do you notice about these two equations?

Sulfuric acid H2SO4 (aq) 2H+ (aq) + SO42-(aq) 1 minute to think and discuss with your partner. Hint: Three points to note. Focus on the product and the state symbols. Sulfuric acid H2SO4 (aq) 2H+ (aq) + SO42-(aq) Hydrochloric acid HCl (aq)  H+ (aq) + Cl-(aq)

In both equations, An anion and a cation is produced. Cation is H+ The acid and ions formed are in aqueous state. Sulfuric acid H2SO4 (aq) 2H+ (aq) + SO42-(aq) Hydrochloric acid HCl (aq)  H+ (aq) + Cl-(aq) Dissociation/ Ionization of acids. i.e. Acid is being ionized in water to form H+ ions and SO42- ions.

Definition of an acid An acid is a substance that produces hydrogen ions, H+(aq), when dissolved in water. Example HNO3(aq)  H+(aq) + NO3-(aq) Nitric Acid Role of water in acidic properties Acids 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.

Chemical properties of acids Acids can take part in the following reactions: Acids + metals Acids + metal carbonates Acids + bases (Metal oxides / Metal hydroxides)

Acid + metals Acids react with reactive metals to form hydrogen gas and salt. General word equation metal + acid  salt + hydrogen Mg(s) + H2SO4(aq)  MgSO4(aq) +H2(g) magnesium Dilute sulfuric acid Magnesium sulfate Hydrogen 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

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) Water Zinc oxide Dilute sulfuric acid Zinc sulfate

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 acids The physical properties of acids

Mini Checkpoint Write the chemical equations for the following reactions: Magnesium and hydrochloric acid Zinc oxide and nitric acid Calcium carbonate and nitric acid