Topic 4 - Chemical Changes Flashcards
What are metal oxides?
Metals reacted with oxygen
What are oxidation reactions?
When the reactant gains oxygen
What happens when metals react with other substances?
The metal atoms form positive ions
What is the reactivity of a metal related to?
It’s tendency to form positive ions
What is the reactivity series?
Lists metals in order of their reactivity towards other substances
What is the reactivity series?
Potassium Sodium Lithium Calcium Magnesium Carbon Zinc Iron Hydrogen Copper
What is the equation for a metal reacting with an acid?
Acid + metal -> salt + hydrogen
Describe how a metal reacts with an acid
Speed of reaction = rate at which hydrogen bubbles are given off
What is the equation for a metal reacting with water?
Metal + water -> metal hydroxide + hydrogen
Where are un reactive metals found? Give an example.
Gold found in earth as metal itself
How are most metals found?
As compounds that require chemical reactions to extract the metal
How can metals less reactive than carbon be extracted form their oxides?
Reduction with carbon
What does reduction involve?
The loss of oxygen
What is oxidation in terms of electrons?
Loss of electrons
What is reduction in terms of electrons?
Gain of electrons
What are redox reactions?
When reduction and oxidation happen at the same time
What neutralises acids?
Alkalis and bases
What is the word equation for the reaction between and acid and a base?
Acid + base -> salt + water
What does the salt produced in a reaction between an acid and an alkali depend on?
The acid used
The positive ions in base or alkali
How can soluble salts be made?
By reacting acids with solid insoluble substances such as metals, metal oxides, hydroxides or carbonates
The solid is added to the acid until no more reacts when the excess solid is filtered off
How do you form solid salts?
Salt solutions can be crystallised
What do acids produce in aqueous solutions?
Hydrogen ions
What do aqueous solutions of alkalis contain?
Hydroxide ions
How do you measure ph?
Universal indicator or ph probe
What is the word equation for neutralisation reactions?
hydrogen ions + hydroxide ions -> water
How do you measure the volumes of acid and alkali solutions that react with each other?
Titrations using a suitable indicator
Give examples of a strong acid
Hydrochloric
Nitric
Sulphuric
What happens to a strong acid in an aqueous solution?
Completely ionised
What happens to a weak acid in an aqueous solution.
Partially ionised
Give examples of weak acids
Ethanoic
Citric
Carbonic
As the ph of an acid increases by one unit what happens to the concentration of the hydrogen ion?
Increases by a factor of 10
What are electrolytes?
The liquids and solutions that are able to conduct electricity because the ions are free to move about within the solution as an ionic compound was melted or dissolved in water
What does passing electric current through electrolytes cause the ions to do?
Positively charged ions move to the negative electrode (cathode)
Negatively charged ions move to the positive electrode (anode)
What is electrolysis?
When ions are discharged at the electrodes producing elements
What happens when a simple ionic compound is electrolysed in the molten state using inert electrodes?
The metal is produced at the catfood and the non-metal is produced at the anode
How can metals be extracted from molten compounds?
Electrolysis
When is electrolysis used to extract metals?
If the metal is too reactive to be extracted by reduction with carbon or if the metal reacts with carbon
Why are large amounts of energy needed during the extraction process of metals by electrolysis?
To melt the compounds and produce electrical current
How is aluminium manufactured?
By the electrolysis of a molten mixture of aluminium oxide and cryolite using carbon as the positive electrode (anode)
What do the ions discharged when aqueous solution is electrolysed using inert electrodes depend on?
The relative reactivity of the elements involved
During electrolysis of aqueous solutions when and where is hydrogen and oxygen produced?
Hydrogen is produced at the cathode if the metal is more reactive than hydrogen
Oxygen is produced at the anode unless the solution contains halide ions when the halogen is produced
Why does electrolysis of aqueous solutions happen in this way?
Because in the aqueous solution water molecules breakdown producing hydrogen ions and hydroxide ions that are discharged
What happens when positively charged ions gain electrons at the cathode?
Reactions are reductions
What happens when negatively charged ions lose electrons at the anode?
Reactions are oxidations
What are half equations?
They show the reactions at the electrodes to make sure the electrons balance
