ACIDS & BASES

1. ACIDS & BASES

2. What are Acids? • An acid is any compound that yields hydrogen ions (H+) or hydronium ions (H3O+) when dissolved in water. • Hydronium ions are really the combination of H+ ions and H2O molecules, i.e. • H+ + H2O  H3O+. • Examples of Common Acids • citric acid (from certain fruits and veggies, notably citrus fruits) • ascorbic acid (vitamin C, as from certain fruits) • vinegar (5% acetic acid) • carbonic acid (for carbonation of soft drinks) • lactic acid (in buttermilk)

3. What are Bases? • A base is any compound that yields hydroxide ions (OH-) when dissolved in water. There are quite a few identifiable bases with hydroxide in the formula such as sodium hydroxide (NaOH) and magnesium hydroxide (Mg(OH)2). • NaOH  Na+ + OH- • Examples of Common Bases • detergents • soap • lye (NaOH) • household ammonia (aqueous)

4. WHAT MAKES THEM DIFFERENT FROM EACH OTHER?

5. What are Indicators? • An indicator is a large organic molecule that works somewhat like a " colour dye". • Whereas most dyes do not change colour with the amount of acid or base present, there are many molecules, known as acid - base indicators , which do respond to a change in the hydrogen ion concentration. • Most of the indicators are themselves weak acids. • Universal Indicator, which is a solution of a mixture of indicators is able to also provide a full range of colours for the pH scale.

6. General reaction types involving acids? REACTION TYPE 1: Acid + Reactive metal  salt + hydrogen Example 1: Reaction between dilute hydrochloric acid and zinc metal can be represented by the equation: 2HCl(aq) + Zn(s) ZnCl2(aq) + H2(g) Represent the ionic equation for the following reaction. Note: To construct the ionic equation you need to look at the aqueous solutions in the reaction and determine whether it has be ionised from the reactant to the product in the reaction. STEP 1: 2H +(aq) + 2Cl -(aq) + Zn(s) Zn2+(aq) + 2Cl -(aq) + H2(g) STEP 2: 2H +(aq) + Zn(s) Zn 2+(aq) + H2(g) {Ionic Equation} Example 2: Reaction between Sulfuric acid and Magnesium Example 3: Reaction between Hydrochloric acid and Lead

7. REACTION TYPE 2: Acid + Metal hydroxide  salt + water Example 1: Reaction between sulfuric acid and sodium hydroxide can be represented by the equation: H2SO4(aq) + 2NaOH(aq) Na2SO4(aq) + 2H2O(l) Represent the ionic equation for the following reaction. Note: To construct the ionic equation you need to look at the aqueous solutions in the reaction and determine whether it has be ionised from the reactant to the product in the reaction. STEP 1: 2H+(aq) + SO42-(aq) + 2Na+(aq) + 2OH-(aq) 2Na+(aq) + SO42-(aq) + 2H2O(l) STEP 2: 2H+(aq) + 2OH-(aq) 2H2O(l){Ionic Equation} Example 2: Reaction between Nitric acid and Calcium hydroxide Example 3: Reaction between Sulfuric acid and Zinc Hydroxide

8. REACTION TYPE 3: Acid + Metal oxide  salt + water Ref: pg 237 • Example 1: Reaction between dilute nitric acid and solid calcium oxide can be represented by the equation: • 2HNO3(aq) + CaO(s) Ca(NO3)2(aq) + 2H2O(l) • Represent the ionic equation for the following reaction. • Note: To construct the ionic equation you need to look at the aqueous solutions in the reaction and determine whether it has be ionised from the reactant to the product in the reaction. • STEP 1: • 2H+(aq) + 2NO3-(aq) + CaO(s) Ca2+(aq) + 2NO3-(aq)+ 2H2O(l) • STEP 2: 2H +(aq) + CaO(s  Ca2+(aq) + 2H2O(l) {Ionic Equation} • Example 2: Reaction between Hydrochloric acid and Potassium oxide • Example 3: Reaction between Sulfuric acid and Sodium oxide

9. REACTION TYPE 4: Acid + Metal carbonate  salt + water + carbon dioxide Example 1: Reaction between nitric acid and solid Magnesium carbonate can be represented by the equation: 2HNO3(aq) + MgCO3(s) Mg(NO3)2(aq) + H2O(l) + CO2(g) Represent the ionic equation for the following reaction. Note: To construct the ionic equation you need to look at the aqueous solutions in the reaction and determine whether it has be ionised from the reactant to the product in the reaction. STEP 1: 2H +(aq) + 2NO3-(aq) + MgCO3(s) Mg 2+(aq) + 2NO3-(aq) + H2O(l) + CO2(g) STEP 2: 2H +(aq) + MgCO3(s) Mg 2+(aq) + H2O(l) + CO2(g) {Ionic Equation} Example 2: Reaction between Hydrochloric acid and Sodium carbonate Example 3: Reaction between Sulfuric acid and Calcium carbonate

10. REACTION TYPE 5: Acid + Metal hydrogen carbonate  salt + water + carbon dioxide • Example 1: Reaction between hydrochloric acid and sodium hydrogen carbonate can be represented by the equation: • HCl(aq) + NaHCO3(aq) NaCl(aq) + H2O(l) + CO2(g) • Represent the ionic equation for the following reaction. • Note: To construct the ionic equation you need to look at the aqueous solutions in the reaction and determine whether it has be ionised from the reactant to the product in the reaction. • STEP 1: • H +(aq) + Cl -(aq) + Na+(aq) + HCO3- (aq) Na+(aq) + Cl -(aq) + H2O(l) + CO2(g) • STEP 2: 2H +(aq) + HCO3- (aq) H2O(l) + CO2(g) {Ionic Equation} • Example 2: Reaction between Nitric acid and Potassium hydrogen carbonate • Example 3: Reaction between Hydrochloric acid and Tin hydrogen carbonate

11. REFERENCES: http://www.elmhurst.edu/~chm/vchembook/182bases.html (acids and bases) http://www.elmhurst.edu/~chm/vchembook/186indicator.html (Indicators) HEINEMANN CHEMISTRY 1 TEXTBOOK (Five general acid reaction type examples)