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 gas Ex. hydrochloric acid + zinc → hydrogen gas + zinc chloride 2HCl (aq) + Zn (s) → H 2 (g) + ZnCl 2 (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 acetate HC 2 H 3 O 2 (aq) + NaHCO 3 (aq) → CO 2 (g) + H 2 O (l) + NaC 2 H 3 O 2 (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 NameChemical Formula Hydrofluoric acidHF (aq) Hydrochloric acidHCl (aq) Hydrobromic acidHBr (aq) Hydrosulfuric acidH 2 S (aq)

NAMES OF ACIDS Oxyacids – related to polyatomic ions (Table 2 Page 269) AcidChemical Formula Related polyatomic ion Polyatomic ion name Acetic acidHC 2 H 3 O 2 (aq)C 2 H 3 O 2 - (aq)Acetate Nitric acidHNO 3 (aq)NO 3 - (aq)Nitrate Carbonic acidH 2 CO 3 (aq)CO 3 -2 (aq)Carbonate Sulfuric acidH 2 SO 4 (aq)SO 4 -2 (aq)Sulfate Phosphoric acidH 3 PO 4 (aq)PO 4 -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 BaseChemical Formula Sodium hydroxideNaOH (aq) Calcium hydroxideCa(OH) 2 (aq) Ammonium hydroxideNH 4 OH (aq) Magnesium hydroxideMg(OH) 2 (aq) Aluminum hydroxideAl(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 IndicatorColour in AcidColour in Base Bromothymol blueYellowBlue PhenolphthaleinColourlessPink Pheol RedYellowRed/pink LitmusRedBlue Methyl orangeRedOrange/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