Pages 46-54

PH reactions, indicators, Cations, Anions, gases and water tests

carbonates test

carbonates test

By adding an acid (HCl) and testing the gas produced for CO2

Products of a reaction between a carbonate and an acid

A salt, water, carbon dioxide

CO2 test

Lime water turns from clear to milky

What is a precipitate

an insoluble solid substance formed from a solution

What is the characteristic of acidic solutions

They are hydrogen ions/ proton donors

What is the characteristic of basic solutions

They are hydroxide (OH^-) donors/ can absorb Hydrogen ions

Name the main four pH indicators

• Universal indicator

• Litmus paper

• Phenolphethalein

• Methyl orange

How does litmus paper indicator work

-Acidic solutions turn orange

-Neutral solutions turn purple

-Alkaline solutions turn blue

It can not show the strength of these solutions

How does Phenolphthalein indicator work

Turns from colourless in acids and neutrals to bright pink in alkalis

How does Methyl orange indicator work

Turns from red in acids to yellow in alkalis

Products of a reaction between a metal and an acid

Salt + Hydrogen

What is the test for sulfates?

• Nitric acid + Barium Chloride solution, BaCl₂ (Can be any acid other than sulphuric).

• A positive test forms a white precipitate

Why is nitric acid added to the test for sulfates and halides?

To react with traces of carbonate or sulfide ions so that they may interfere with the results

What are halides

Ions of halogens

What is the test for halides

Nitric acid + silver nitrate

What is the result of a positive chloride test

A white precipitate (Silver chloride, AgCl)

What is the result of a positive bromide test

A cream precipitate (Silver bromide, AgBr)

What is the result of a positive Iodine test

A yellow precipitate (Silver Iodide, AgI)

What reactants create soluble salts

An acid + an insoluble base

What is the difference between a base and an alkaline

An alkaline is a base which can be disolved in water

Describe the procedure of forming a soluble salt

• The acid is heated

• The insoluble base is added to the acid in excess

• The solution is filtered to remove excess solid

• The solution is slowly heated to evaporate some of the water

• The solution is left to cool and the salt crystalises

• Filter of the solid crytals and let them dry

Give an example reaction equation which would produce a soluble salt

Copper oxide (CuO) + Sulfuric acid (H₂SO₄) reacts to form Copper sulfate (CuSO₄₎ + water (H₂O)

What is the test for water

Dehydrated copper sulfate crytals turn from white to blue in the presence of water

What is the positive test for Lithium ions (Li⁺)

Red flames

What is the positive test for Sodium ions (Na⁺)

Yellow flames

What is the positive test for Potassium ions (K⁺)

Lilac flames

What is the positive test for Calcium ions (Ca²⁺)

Orange-red flames

What is the positive test for Copper ions (Cu²⁺)

Blue-green flames

How is the flame test for metal cations conducted?

• A platinum or nichrome wire piece is cut

• The wire is dipped in HCl acid to clean it

• It is then dipped in the sample metal and held over the blue part of the bunsen flame

• The wire can be cleaned and used again

what is the cations coloured precipitate test

Adding a few drops of sodium hydroxide (NaOH) to a metal ion sample which should form a colourful precipitate

What is the result of a Copper II (Cu²⁺) test?

A blue precipitate

What is the result of an Iron II (Fe²⁺) test?

A sludgy green precipitate

What is the result of an Iron III (Fe³⁺) test?

A reddish brown precipitate

What is the result of an ammonium ion test?

Red litmus paper turns blue

How is an ammonium ion test conducted?

• A few drops of Sodium hydroxide (NaOH) are added to an ammonium solution

• Damp litmus paper is held over the test tube to pick up on ammonia gas

What is the test for chlorine gas?

Damp blue limus paper turns white

What is the test for Oxygen gas?

It relights a glowing splint

What is the test for Hydrogen gas?

It burns with a squeaky pop

What is the test for ammonia gas?

Damp blue litmus paper turns red

Results of a reaction between an acid and a metal hydroxides

A salt + water

Results of a reaction between an acid and a metal oxides

A salt + water