Acids and Bases (IGCSE Chemistry)

Litmus in an acid

blue to red

Litmus in a base

red to blue

methyl orange in an acid

red

methyl orange in a base

yellow

Phenolphthalein indicator in bases and acids

Indicator which is clear in acidic solution and pink in basic solution.

acids react with...

-metals

-bases (metal oxides, hydroxides and ammonia)

-carbonates to form salts

acid + metal

salt + hydrogen

acid + hydroxide

salt + water

acid + metal oxide

salt + water

acid + carbonate

salt + water + carbon dioxide

alkali

soluble bases

what do bases do to acids

They neutralise acids to form a salt.

what is used when soil is too acidic?

calcium oxide

calcium hydroxide

calcium carbonate

-they neutralise the soil

-they are chosen because they are cheap and not very soluble so rain won't wash them away

what ions do acids contain

hydrogen ions (H+)

How do strong acids ionize?

completely ionize in water

How do weak acids ionize?

they only partially ionize in water

examples of strong acids

hydrochloric acid, nitric acid, sulfuric acid

examples of weak acids

Ethanoic acid

Citric acid

what ions do alkalis contains

hydroxide ions

examples of strong alkalis

sodium hydroxide, potassium hydroxide

examples of weak alkalis

ammonia solution

spectator ions

they do not participate in the reaction

what is a proton donor

an acid ALWAYS

what is a proton acceptor

base ALWAYS

metals form what when they react with oxygen?

metal oxides (usually)

they are basic

they neutralize acids

Are non-metal oxides acidic or basic?

acidic

examples of acidic oxides

carbon dioxide CO2

sulfur oxide SO2

nitrogen dioxide NO2

phosphorus pentoxide P4O10

examples of basic oxides

sodium oxide Na2O

calcium oxide CaO

Iron(iii) oxide Fe2O3

copper(ii) oxide CuO

What are amphoteric oxides?

oxides that are both basic and acidic

examples of amphoteric oxides

aluminium oxide Al2O3

Zinc oxide ZnO

lead(ii) oxide PbO

what are neutral oxides?

oxides that are neither basic nor acidic

examples of neutral oxides

water H2O

Carbon monoxide CO

dinitrogen oxide N20

they have no effect on litmus paper

pH is 7