4. Chemical changes Flashcards
What method is used to extract metals that are more reactive than Carbon?
Electrolysis
What method is used to extract metals that are more reactive than hydrogen, but less reactive than carbon?
Reduction with carbon
Define acid in terms of pH
A substance with a pH of less than 7
What does (aq) stand for?
Aqueous: when something is dissolved in water
State the three common acids and give their formulae
Hydrochloric acid, HCl(aq), Sulphuric acid, H?SO?(aq), Nitric acid, HNO?
How do you measure pH?
With an indicator or pH probe.
What is a base?
A metal oxide, hydroxide or carbonate that will react with an acid. E.g. copper oxide
What is an alkali?
A soluble base. E.g. sodium hydroxide
Which ions are always present in a solution of an alkali?
OH?
What type of salts are formed by the three main acids?
Hydrochloric acid produces chlorides, sulphuric acid = sulphates, nitric acid = nitrates
Which ions always react together in a neutralization reactions between acids and alkalis?
H? and OH?
metal + acid ?
? salt + hydrogen gas
metal hydroxide + acid ?
? salt + water
metal oxide + acid ?
? salt + water
metal carbonate + acid ?
? salt + water + carbon dioxide
What is electrolysis?
Using electricity to break down a substance
Do positive ions move to the anode or the cathode?
Cathode
Do negative ions move to the anode or the cathode?
Anode
In the electrolysis of solutions, what is produced at the cathode?
Hydrogen, unless the metal ion present is less reactive
In the electrolysis of solutions, what is produced at the anode?
Oxygen, unless the other negative ion present is a halide ion
What is oxidation?
Oxidation is the loss of electrons
What is reduction?
Reduction is the gain of electrons
What is a strong acid?
An acid which completely splits up into its ions in water. Eg. HCl
What is a weak acid?
An acid which will have some molecules which do not split up into their ions. Eg. Ethanoic acid
What is a concentrated acid?
An acid where there are lots of acid particles in the water.
