Salts And Electrolysis Flashcards
What are the similarities between alkalis and bases?
- both release ions in water
What does an ‘ acid + metal ‘ make?
A salt + hydrogen
What happens at the negative electrode in the electrolysis of aqueous solutions? 2
- The less reactive element ( between hydrogen and the metal ) is produced at the negative electrode
- and the metal will stay in solution
Why would thermosoftening polymers not be suitable for packaging very hot food?2
They would melt because of their low melting point
because of their weak intermolecular forces
When electrolysis happens in water what gas is given off?
Oxygen gas as discharge from hydroxide ions
What is two ways to identify a base?2
- hydroxides
- oxides
What happens when you react an acid with a metal?
Hydrogen gas is formed along with the salt
What is a salt?
A compound formed in a neutralisation reaction
Define electrolysis?
The process of passing an electric current through an ionic compound it through a molten substance Causing decomposition (splitting up)
What happens to ions in electrolysis?
Positive ions move to the negative electrode while negative ions move to the positive electrode
In electrolysis of electrons are gained what is the process called?
Reduction
Why can carbon nanotubes be used as lubricants?
Nanotubes can slide over eachother
Because no covalent bonds between the nanotubes
How do you make an insoluble salt? Eg with lead nitrate solution and potassium iodide solution
Add PIS to LNS and stir in a beaker
Precipitate of lead iodide formed
This can be filtered off the solution
Precipitate washed, distilled water and dried
Why can graphite conduct electricity?
Delocalised electrons can move through the graphite
What happens when two ions are attracted to an electrode?
The less reactive element gets discharged
List some protestors of alkalis?3
- soluble in water
- produce OH- ions
- pH 8-14
Why type of substance provides oh- ions?
Alkali
What ions are formed by alkalis in solutions?
OH- ions
What happens at the negative electrode during the electrolysis of brine?4
- Positive hydrogen ions are attracted to the negative electrode, as are the sodium ions
- hydrogen ions are less reactive so get discharged
- sodium ions stay in solution as they are more reactive
- the hydrogen atoms formed bond together and are given off as hydrogen gas
Why do farmers put ammonium nitrate on their farmland?
It provides minerals that help plants to grow
What happens at the positive electrode in the electrolysis of aqueous solutions?
Hydroxide ions from water are often discharged and oxygen gas
In the electrolysis of aluminium what happens at the negative electrode and involving the electrode? (O2-) 3
Each oxide ion loses two electrons
The ions turn into oxygen atoms
They bond in pairs to from molecules of oxygen gas
The oxygen reacts with the positive carbon electrodes making carbon dioxide gas
What ions are formed by acids in solutions?
H+ ions
What happens to the products of electrolysis if the reaction happens in water? 2
- The less reactive element ( between hydrogen and the metal ) is produced at the negative electrode
- and the metal will stay in solution
Why use molten?
Ionic substances don’t conduct electricity
When melted ions are free to move and carry charge
Explain how an object is electroplated?4
- the metal to be plates is used as the negative electrode
- the positive electrode is made from the plating metal
- at the positive electrode the playing metal is oxidised
- at the negative electrode the plating metal is reduced
Describe the structure of a metal?
Lattic of positive ions
With delocalised electrons
What is a cryolite and why is it used in the extraction of aluminium oxide?
The molten cryolite lowers the melting point making the reaction more efficient
What method could be use to separate a precipitate from solution?
Filters room
What does using the word ‘weak’ in terms of an acid mean?
The acid is partially ionised in water
What state are all carbonates?
Solids
Sum up how to make an insoluble salt in two sentances?
Combining two different soluble salts
React together to form a precipitate
Uses of brine products?
Chlorine = bleach which kills bacteria
Pure hydrogen =’margarine
Sodium hydroxide = bleach, soap, paper
Why do we electroplated objects?2
- for industrial purposes for protection
- for cosmetic purposes for attractiveness
List some properties of acids?2
- pH 1-6
- produce H+ ions in solution
Why does a catalyst not have to be replaced often?
It is not used up
What do you observe when magnesium reacts with an acid?
Gets hot Hydrogen produced (bubbles) Magnesium goes into solution
Why can metals be shaped?
Made of layers
Which can slip over eachother
What are the products of the electrolysis of brine? At what electrode?
Hydrogen at the + electrode
Chlorine at the - electrode
Sodium hydroxide at the - electrode
Define neutralisation?
The chemical reaction of an acid with a base in which they cancel each other out, forming a salt and water (canton dioxide)
What is the difference between an alkali and a base?
Alkalis are bases that dissolve in water
In electrolysis of electrons are lost what is the process called?
Oxidation
In electrolysis what is it that provides the electrodes with a charge?
Electricity
Describe the process of making crystals?
Add insoluble metal to a beaker with an acid + stir Warm gently with tripod When reaction is complete Filter to remove excess metal oxide Evaporate off water Leave to form crystal
When two soluble salts react to make an insoluble salt what is this called?
A precipitate reaction
Why are electrodes used up in the process of electrolysis?2
Oxygen gas is produced at the electrode
So the oxygen reacts with the electrode to form Carbon dioxide wearing it down
What charge do electrons have?
-1
What happens at the positive electrode during the electrolysis of brine?3
The negative chloride ions are attracted to the positive electrode
They each loose 1 electron (oxidised)
The chlorine atoms bond together in pairs and are given off as chlorine gas
Why does sodium iodine only conduct electricity in solution?
- the particles are free to move
Common acids?3
Hydrochloride acid
Sulphuric acid
Nitric acid
In the electrolysis of aliminium what happens at the negative electrode? (Al3+) and in what form?
- each aluminium ion gains 3 electrons
- the jobs turn into aluminium atoms
- the metal is formed as molten
What is an acid in terms of ions?
Something that produces hydrogen ions in solution
What is the product of the electrolysis of aluminium oxide?
Aluminium + oxygen
Which electrode would negative ions move towards?
The positive electrode to become neutral atoms
What are the products of brine used for?6
Chlorine : bleach, killing bacteria
Hydrogen : making margarine
Sodium hydroxide : bleach, paper making, soap
Why is molten used for electrolysis?
So ions can move
What is the difference between ‘ ate ‘ and ‘ ide ‘?2
Contains oxygen
Without oxygen
What is an alkali in terms of ions?
A base that is soluble in water which produces hydroxide ions in solution
What type of substance does electrolysis work for?
Ionic substances
Define electroplating?
The process of depositing a thin layer of metal on an object during electrolysis
What does ‘Acid + base’ make?
salt + water
In a crystals experiment, why heat the mixture?
To increase the rate of reaction
What is a neutralisation reaction?
When an acid neutralised by a base
Example of an alkai?
Sodium hydroxide solution
Which electrode would positive ions move towards?
Negative electrodes to become neutral atoms
What does an ‘acid + metal hydrocarbonate’ make?
A salt + water + carbon dioxide
What does nitric acid always create?
Nitrates
What the method for making an insoluble salt?3
- combine two different soluble salts
- these salts react to form an insoluble salt
- the insoluble solid formed is called a precipitate
What does an ‘acid + metal carbonate’ make?
A salt + water + carbon dioxide
How do you make soluble salts from metals?
Reacting acids with
Not all metals are suitable
Some too reactive and others are not reactive enough
How do you make soluble salts from insoluble bases?
Reacting acids with
The base is added to the acid until no more will react and the excess solid is filters off
How do you make soluble salts from alkalis?
Reacting acids with
An indicator can be used to show when the acid and alkali have completely reacted to produces a salt solution
How can insoluble salts be made?
By mixing appropriate solutions of ions so a precipitate is formed
Precipitation can be used to remove unwanted ions from solution
Eg treating wait for drinking or in treating effluent
What are soluble hydroxides?
Alkalis
Ammonia dissolved in water to produce what?
An alkaline solution to produce ammonium salt
What does an electrolysis of sodium chloride solution produce?
Produced hydrogen and chlorine
Sodium hydroxide solution
What is chlorine used for?
Bleach and plastics
What 3 ways can you make a soluble salt?
Acid + metal
Acid + alkali
Acid + base
When making salts, when will an acid react with a metal to make a salt?
When it is above hydrogen in the reactivity series
How can you test the speed of an acid + metal reaction?
The number of hydrogen bubbles given off
How do you make a salt from an acid + base?
Excess base is added to acid
Until no more will react
Excess is filtered off
What type is salt does Hydrochloric acid produce?
Chloride salts
How do you make nitrate salts?
Nitric acid + (base/metal/alkali)
How do you make sulphate salts?
Sulphuric acid + (base/metal/alkali)
How do you make nitrate salts?
Nitric acid + (base/metal/alkali)
What 3 ways can you measure a reaction?
Measuring precipitate - faster it disappears faster the reaction
Volume of gas given off - more given off faster reaction
Mass balance - how quickly mass drops
What does cryolite do?
Lowers melting point of aliminium oxide so it’s cheaper to carry out
What are electrodes made of?
Carbon
How is aluminium manufactured?
By the electrolysis of molten mixture of aluminium oxide and cryolite
What happens at the negative electrode?
Hydrogen is produced unless the metal is more reactive than hydrogen
The more reactive ions stay in solution
What happens in the positive electrode?
If hydroxide ions and halide ions are present, w halide ion will be produced (chlorine bromine iodine)
If no halide oxygen is produced
What does the electrolysis of sodium chloride solution produce?
Hydrogen
Chlorine
Sodium hydroxide
What happens if something is more reactive than hydrogen?
Hydrogen is formed
Other substance stays in solution
What has to happen for a substance not to be deposited at the negative electrode?
It has to be more reactive than hydrogen
Less reactive hydrogen is deposited
Where does the object to be plated go?
To the negative electrode
Where does the plating metal go?
The positive electrode
What is brine?
Sodium chloride solution