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 Strong Acid rain, car batteries, the lab.

 Nitric acid HNO3 Strong Acid rain, in the

lab.

 Ethanoic (acetic)

acidCH3COOH Weak Vinegar

 

Methanoic (formic) acid

HCOOH Weak Ant & nettle stings, descalers

  Citric Acid C6H8O7 Weak 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

CarbonateCalcium 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

Neutralization

• Reactions in which an acid is added to a base cause neutralization

• This usually results in a salt and water

• IN the case of carbonate bases it results in a carbonate salt, water, and carbon dioxide

Titration

• A titration is a process where by the concentration of an unknown acid or base is determined by using a solution with a known concentration.

• This solution is known as the standard solution.

• The formula M1V1=M2V2 is used to determine the molarity of the unknown