Acids and Bases

And neutralization reactions

Acids and Bases

• An acid is a substance that produces hydrogen ions in solution.

HCl H+ + Cl-

• A base is a substance that produces hydroxide ions in solution.

NaOH Na+ + OH-

Acids

• Substances that release hydrogen ions (H+) when mixed in water

• Physical Properties:– Sour tasting– Wet to the touch when in solution– Water soluble– Good conductors of electricity, therefore

electrolytes

Acids

• Chemical Properties– React with metals to produce hydrogen gas– Corrosive– Make chemical indicators change colour– React with bases to produce a neutral

solution

Acids

• Examples:

Bases

• Substances that release hydroxide ions (OH-) when mixed in water. Also called alkaline

• Physical Properties:– Bitter tasting– Slippery to the touch when in solution– Water soluble– Good conductors of electricity, therefore

electrolytes

Bases

• Chemical Properties– Corrosive– Make chemical indicators change colour– React with acids to produce a neutral solution

Bases

• Examples:

Chemical Indicators

• Are solutions that change colour in acids and in bases

• Can be either – natural or – synthetic

Chemical Indicators

• Litmus paper:– Base turns it Blue!– Acid turns it Red!

Universal Indicator is a mixture of chemicals that changes colour through a wide range of pH values

The pH scale

• A numerical scale used to show how acidic or basic a solution is

• pH stands for “power of hydrogen”

The pH scale

• pH is a logarithmic scale which means that every unit on the scale represents a tenfold (10X) effect on the concentration of the solution

The pH scale: Logarithmic

• This means that pH 3 is 10 times more acidic than ph 4. • If the value changes by more than one number you must

multiply – ex. From pH 5 to pH 8 = 10 x 10 x 10 (3 steps = 10

multiplied by itself 3 times)

Naming Acids

• A binary acid forms when an H+ bonds with a non-metal

• HF (aq), HCl (aq), HBr (aq), HI (aq), H2S (aq), and H3P (aq) are some common binary acids

• To name them, use the following structure:– “hydro + ______ ic acid”

Naming Acids

• An oxyacid has a non-metal and an oxygen component

• H3PO4, HClO3, HIO3, H2SO4, HBrO3, H2CO3, and HNO3 are some common oxyacids

• To name them:– “_____________ ic acid”

Naming Bases

1. Name the metal

2. Name the polyatomic (i.e. hydroxide)• Example

– Mg(OH)2 – magnesium hydroxide

Neutralization Reactions

• A type of double displacement reaction• Acid + Base Water + Salt• A salt is an ionic compound. The pH of the

products is around 7 (neutral)

Example

hydrochloric acid + sodium hydroxide water + sodium chloride

Practise!!

• Try the practise questions on your worksheet!

Naming Acids and Their Ions• There are two main kinds of acids: binary

acids and oxoacids.

• A binary acid is composed of two elements: hydrogen and a non metal. The general formula for a binary acid is HX, where X is the non-metal. (HBr and HCl are two examples).

• To name a binary acid• Attach the prefix hydro• Use the non-metal name as the root• Attach the suffic “ic”• Add the word acid

• HF• Hydrofluric acid

• HCl• Hydrochloric acid

• HBr• Hydrobromic acid

• HI• Hydroiodic acid

• H2S

• Hydrosulfuric acid

• An oxoacid (oxyacid) is an acid formed from a polyatomic ion that contains oxygen, hydrogen, and another element.

• For anions that end in “ate”, change the ending to “ic” and add the word acid

•ClO3- is chlorate

•HClO3- is called chloric acid

• For anions that end in “ite”, change the ending to “ous” and add the word acid.

• ClO2- is chlorite

• HClO2- is chlorous acid

• The prefixes hypo and per remain as part of the acid name.

• ClO4- is perchlorate

• HClO4- is perchloric acid