PROPERTIES OF ACIDS & BASES

WEEK OUTLINE:

Monday: Properties of Acids & Bases

Tuesday: Acid Precipitation

Wednesday: Properties of Acids & Bases Lab Stations

Thursday: Neutralization Reactions

Friday: Acid/Base Quiz Making an Indicator – Acids & Bases at Home Lab

NEXT WEEK:

Monday (Dec 14): Review Class

Tuesday (Dec 15): Chemistry Test

Wednesday- Friday (Dec 16-18) Start Climate Change Unit

WHAT DO YOU THINK?

Page 265: True or False? Stomach acid can dissolve metals like a coin

in a child’s stomach? We all contribute to the production of acid

precipitation? Even diet soda drinks can cause tooth decay? Medications for heartburn work by cooling

the stomach? All acids are dangerous? Soft drinks can be used to make spilled drain

cleaner safer?

PROPERTIES OF ACIDS AND BASES

Young children like to explore by putting things in their mouths

Occasionally objects get swallowed! Coins are the most common object to be

swallowed Once in the stomach, the coin in bathed in a

corrosive mixture that includes hydrochloric acid (HCl (aq)) and other digestive juices

The concentration of HCl in your stomach is about the same as ones we have used in class - what do you think happens to the coin?

PROPERTIES OF ACIDS

Chemists classify substances by their properties

Acids - are substances that react with metals and carbonates, conduct electricity, turns blue litmus red, and neutralize bases

Acids also taste sour, but you should never taste chemicals in a lab!

Very useful in food industry - act as preservatives (vinegar and lemon juice)

PROPERTIES OF ACIDS

Reaction with Metals Acids react with metals to produce

hydrogen gasEx. hydrochloric acid + zinc →

hydrogen gas + zinc chloride 2HCl (aq) + Zn (s) → H2 (g) + ZnCl2 (aq)

PROPERTIES OF ACIDS

Reaction with Carbonates Acids react with carbonates to

produce carbon dioxide gas Ex. acetic acid + sodium hydrogen

carbonate → carbon dioxide + water + sodium acetateHC2H3O2 (aq) + NaHCO3 (aq) → CO2 (g) + H2O (l) + NaC2H3O2 (aq)

PROPERTIES OF ACIDS

Electrical Conductivity Many acids are good conductors of

electricity A solution can only conduct electricity

if it contains ions Since acids are molecular compounds

they do not contain ions

PROPERTIES OF ACIDS

Electrical Conductivity (Continued) However, collisions with water

molecules break acid molecules apart to form cations (hydrogen ions) and anions

Ex. Hydrochloric acid forms hydrogen and chloride ions: HCl (aq) → H+ (aq) + Cl- (aq)

CHEMICAL FORMULAS OF ACIDS

All acids produce hydrogen ions when dissolved in water

Hydrogen ions give acids their properties The chemical formula of an acid begins with

an H and is usually followed by an “(aq)” This is because an acid shows its properties

when dissolved in water Hydrogen chloride - gas that would dissolve

in water in lungs when inhaled = forming highly corrosive hydrochloric acid

NAMES OF ACIDS

Two common groups of acids: Binary Acids (Table 1 Page 269)

Acid Name Chemical Formula

Hydrofluoric acid HF (aq)

Hydrochloric acid HCl (aq)

Hydrobromic acid HBr (aq)

Hydrosulfuric acid H2S (aq)

NAMES OF ACIDS

Oxyacids – related to polyatomic ions (Table 2 Page 269)

Acid Chemical Formula

Related polyatomic ion

Polyatomic ion name

Acetic acid HC2H3O2 (aq) C2H3O2- (aq) Acetate

Nitric acid HNO3 (aq) NO3- (aq) Nitrate

Carbonic acid H2CO3 (aq) CO3-2 (aq) Carbonate

Sulfuric acid H2SO4 (aq) SO4 -2 (aq) Sulfate

Phosphoric acid H3PO4 (aq) PO4 -3 (aq) Phosphate

PROPERTIES OF BASES

Bases - conduct electricity, change the colour of acid-base indicators, feel slippery and taste bitter

PROPERTIES OF BASES

Electrical Conductivity Bases are electrolytes, meaning their

solutions are good conductors of electricity Ex. NaOH (sodium hydroxide) is an

electrolyte because in water it separates into ions as it dissolves NaOH (s) → Na+ (aq) + OH- (aq)

Many common bases are ionic compounds - they are made up of ions (unlike acids)

As they dissolve in water, their ions are released

NAMES AND CHEMICAL FORMULAS OF BASES

Table 4 Page 271

Base Chemical Formula

Sodium hydroxide NaOH (aq)

Calcium hydroxide Ca(OH)2 (aq)

Ammonium hydroxide NH4OH (aq)

Magnesium hydroxide Mg(OH)2 (aq)

Aluminum hydroxide Al(OH)3 (aq)

Sodium hydrogen carbonate (baking soda)

NaHCO 3 (aq)

COLOUR WITH ACID-BASE INDICATORS

A substance that changes colour depending on the acidity or basicity of the solution is known as an acid-base indicator

COLOURS OF COMMON SYNTHETIC ACID-BASE INDICATORS

Table 3 Page 270

Indicator Colour in Acid Colour in Base

Bromothymol blue Yellow Blue

Phenolphthalein Colourless Pink

Pheol Red Yellow Red/pink

Litmus Red Blue

Methyl orange Red Orange/Red

THE PH SCALE

pH scale - a numerical scale of all the possible values of pH from 0 to 14

pH is a measure of how acidic or basic a solution is

A solution with a pH of 7 is considered neutral

A solution with pH of less than 7 is considered acidic

A solution with pH of greater than 7 is considered basic

THE PH SCALE CONTINUED

Solutions with highest hydrogen ion concentration are near zero on pH scale

Solutions with highest concentrations of hydroxide ions are near 14 on pH scale

Can use the words “acidity” or “basicity” to describe the properties of acids or bases

ACID AND BASE HOMEWORK

Page 271 #1-5