Acids and Bases Chapter 23

Common Acids and Name Formula Strong/Weak Where is it found?   Hydrochloric acid HCl Strong The stomach, in the lab. Sulphuric acid H2SO4 Acid rain, car batteries, the lab. Nitric acid HNO3 Acid rain, in the lab. Ethanoic (acetic) acid CH3COOH Weak Vinegar Methanoic (formic) acid HCOOH Ant & nettle stings, descalers Citric Acid C6H8O7 Citrus fruits

Acids Acids are H+ or proton donors: Properties Acids taste sour (e.g. vinegar, lemon juice). Acids are harmful to living cells. Aqueous solutions of all acids contain hydrogen ions, H+.

Water is needed

Common Bases Name Formula Where is it found? Sodium hydroxide (caustic soda) NaOH Oven cleaners, in the lab. Calcium hydroxide Ca(OH)2 Soil lime, limewater Magnesium oxide (magnesia) MgO Indigestion tablets Calcium carbonate CaCO3 Limestone, soil lime Sodium hydrogencarbonate (bicarbonate) NaHCO3 Baking powder Ammonia NH3 Cleaning fluids, in the lab.

Base properties Most bases are oxides, hydroxides or carbonates of metals Soluble bases are known as alkalis. Aqueous solutions of alkalis contain hydroxide ions, OH-. Bases taste bitter. . Bases feel slippery

Base and indicators Bases turn red litmus blue.  A common indicator, used to detect the presence of a base, is phenolphthalein which, when mixed with a base, turns pink. Bases release hydroxide ions in water solutions.  NaOH (s)  +  H2O (l)   à   Na1+ (aq)   +   OH1- (aq) NH4OH  (aq)  ß -> NH41+ (aq)  +  OH1-  (aq)   

pH scale Water is defined as having a pH value of 7- neutral. Acidic solutions have pH values below 7. Alkaline (basic) solutions have pH values above 7. pH is a measure of the number of hydronium or hydroxide ions Logrithimic scale

pH scale

Reactions of Acids With metals  Metals above copper in the reactivity series will react with acids, giving off hydrogen gas. The metal dissolves, forming a salt.   METAL + ACID ® SALT + HYDROGEN ex. Mg(s) + H2SO4(aq) ® MgSO4(aq) + H2(g) This is why acids corrode metals, and must be stored in glass containers.

Base reactions With bases (metal oxides and hydroxides)  The base dissolves in the acid and neutralises it. A salt is formed. ACID + BASE ® SALT + WATER ex.       H2SO4(aq) + CuO(s) ® CuSO4(aq) + H2O(l) With metal carbonates  Metal + Base Salt + water + CO2 2HCl(aq) + CaCO3(s) ® CaCl2(s) + H2O(l) + CO2(g)  

Indicators Indicators- an organic compound that turns color in the presence of an acid or base

Naming Acids Prefix is always hydro Name the second element with the suffix -ic HCl – hydrochloric HF- Hydrofluoric

For the acid containing the most common polyatomic ion of its group simply use the first part of the polyatomic name and follow with the suffix ic. For the acid containing the polyatomic with one less oxygen than the ic, use the suffix ous. For the acid containing the polyatomic with two less oxygens than the ic, use the prefix hypo and the suffix ous. For an acid containing the polyatomic with one more oxygen than the ic, use the prefix per and the suffix ic.

Naming Bases and Salts Follow regular naming rules

Acid Reactions ACID + BASE  SALT WATER Hydrochloric Acid Sodium Hydroxide Sodium Chloride Water HCl NaOH NaCl H2O

ACID + METAL  SALT HYDROGEN GAS Hydrochloric Acid Magnesium Magnesium Chloride Hydrogen HCl Mg MgCl2 H2

ACID + CARBONATE SALT WATER CARBON DIOXIDE GAS Hydrochloric Acid Calcium Carbonate Calcium Chloride Water Carbon Dioxide

Molarity Molarity indicates the concentration Given in the unit Moles/Liters Moles is the SI unit for quantity- it indicates 6.022 x1022 atoms or molecules of a substance It is equal to the atomic weight of the element in grams Ex. 16.00 g of O is one mole 32.00 g of O2 one mole