ACIDS &

BASES

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)

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)

WHAT MAKES THEM DIFFERENT FROM EACH

OTHER? PROPERTIES OF :

ACIDS BASE

* Tends to be corrosive to metals and skin

* Have a slippery feel

* Taste Sour * Turns red litmus paper blue

* Reacts with bases * Reacts with acids

* Has a relatively low pH * Has a relatively high pH

* Changes the colour of some indicators

* Are caustic

* Turns blue litmus paper to red

* Taste Bitter

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.

The most common indicator is found on "litmus" paper. It is red below pH 4.5 and blue above pH

8.2.

Colour Blue Litmus

Red Litmus

Acid Turns red

Stays same

Base Stays same

Turns Blue

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) Zn 2+

(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

General reaction types involving acids?

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) + SO4

2-(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

REACTION TYPE 3: Acid + Metal oxide salt + waterRef: 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

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

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

REFERENCES:

1. http://www.elmhurst.edu/~chm/vchembook/182bases.html (acids and bases)

2. http://www.elmhurst.edu/~chm/vchembook/186indicator.html (Indicators)

3. HEINEMANN CHEMISTRY 1 TEXTBOOK (Five general acid reaction type examples)