Chemical Changes Flashcards
(44 cards)
Electrolysis
Why would you observe a pink soild [ coppor metal] formed at the negative electrode in coppor sulfate solution.
Because ions are reduced and deposited.
Deposited - The process where a metal forms a solid layer on an electrode (the cathode) through the reduction of its ions.
Electrolysis
Why would bubbles form at the negative electrode in a sodium chloride solution?
Electricity passes through causing water to spilt into hydrogen and cholrine gas which causes bubbles forming at the electrode tip.
Electrolysis
What is the process of chemical cell?
Cells that are used in chemical reactions to produce electricity.
Electrolysis
What forms at the cathode?
What forms at the anode?
What is the general rule for
determining which anion is oxdized at the anode?
Metal
Non-metal
If the anion is halide ion it is oxidized at the anode.If the anion is not a halide ion, oxygen is produced at the anode.
Electrolysis
List the reactivity series.
Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
Carbon’
Zinc
Iron
Hydrogen
Coppor
Silver
Gold
Electrolysis
Some students investigated the electrolysis of copper nitrate solution using inert
electrodes.
The students investigated how the mass of copper produced at the negative
electrode varied with:
* time
* current
Some of the copper produced did not stick to the negative electrode but fell
to the bottom of the beaker.
Suggest how the students could find the total mass of copper produced [4]
Filter the mixture.[1]
Wash and dry the coppor to remove and residue.[1]
Weight the coppor collected.[1]
Add to incease in the mass of the electrode[1]
Why is graphite used in electrodes? [2]
Graphite can conduct electricity.
It is unreactive.
Why is graphite unreactive?
Due to the carbon atoms which are bound in layers by strong covalent bonds, making it difficult to break down or react with other substances.
Electrolysis
What is an alloy?
A mixture of metals
Electrolysis
What is the definition of crystallisation?
It is used to seperate soluable solid from a solution through evapouration of the solvent.
Electrolysis
Aluminium is produced by electrolysing a molten mixture of alminium oxide and cryolite.
Explain why a mixture is used as the electrolyte instead of using only alminium oxide?
Mixture has lower melting point than aluminium oxide.[1]
so less energy is needed[1]
Electrolysis
1.What is cryolite and how is it used? [ state the chemical formuala]
2.Why is it used as a mixture as the electrolyte instead of using only aluminium oxide during the extraction of aluminium oxide? [2]
Cryolite is a white or colorless mineral with the chemical formula:
✅ Na₃AlF₆ → Sodium aluminum fluoride.
Cryolite is mixed with aluminum oxide, creating a mixture that acts as the electrolyte.
- Because it is a mixture that has lower melting point than aluminium oxide[1] so less energy is needed.[1]
Electrolysis
Oxygen is produced at the postive electrode.
Explain why the postive electrode must be continually replaced?[3]
The electrode reacts with oxygen[1]
The electrodes are graphites[1] which is pure carbon.
so carbon dioxide is produced.[1]
Electrolysis [ Textbook]
Why is aluminium extracted from the ore bauxite?
Because it contains aluminium oxide (Al₂O₃)
Reactivity of Metals
How do you calculate uncertainty?
(Largest value - smallest value)/2
Reactivity of Metals.
Tungsten (W) is a metal.
Tungsten is extracted from tungsten oxide (WO3).
All other solid products from the extraction method must be separated from
the tungsten.
The table below shows information about three possible methods to extract
tungsten from tungsten oxide.
Method
Reactant
Relative cost of
reactant
Products
(2)
(1)
(3)
1
Carbon
2
Hydrogen
Low
Tungsten solid
Carbon dioxide gas
Tungsten carbide
solid
High
3
Iron
Tungsten solid
Water vapour
Low
Tungsten solid Iron
oxide solid
Evaluate the three possible methods for extracting tungsten from tungsten
oxide.
Look at the key key word evaluate - pros and cons of each method.
Use terms like “most and least” if you have to. [4]
Carbon and iron are the cheapest reactant.[1]
However they need to seperate the solid products which is time-consuming.[1]
In method 2, the water vapour produced will escape [1]
There is no serperation of soild needed.[1]
Raectivity of Metals
As you go down Group 1 the reactivity increases, which means the electrons are further from the nucleus. How does that impact the reactivity of Group 1 metals? [2]
There is less attraction between nucleus and outer shell. [1]
so that atom loses an electron more easily.[1]
Reactivity of Metals
What is the shielding effect, and how does it affect electron loss? [2]
The shielding effect is when inner electron shells reduce the pull of the nucleus on the outer electron.
This makes the outer electron easier to lose.
Reactivity of Metals
Why does a smaller atom hold onto its electrons more tightly? [1]
In smaller atoms, the outer electrons are closer to the nucleus, so the attraction is stronger, making it harder to lose electrons.[1]
Reactivity of Metals
What is the structure of an ionic compund?[3]
It has a giant ionic lattice strcuture[1] the ions are closely packed in a regular lattice arrangement[1] and they have strong electrostatic forces of attraction between oppsoitely charged ions[1]
Reactivity of Metals
Why are alloys harder than pure metal?[2]
Because they have different sized atoms[1] which means that the layers slide over each other less easily[1]
Reactivity of Metals
Why is the temeprtaure change used to compare the reactivity of an unknown metal? [2]
The temperature change is a simple and reliable way to compare the energy released by different metals.
A larger temperature rise, the more reactive the metal.
Reactivity of Metals
)
A student wants to compare the reactivity of an unknown metal, Q, with that
of zinc.
Both metals are more reactive than silver.
The student is provided with:
* silver nitrate solution
* metal Q powder
* zinc powder
* a thermometer
* normal laboratory equipment.
The metal is added to the silver nitate the solution.
Why is that? [1]
Describe the remaining steps the student could have done to compare the reactivity of metal
Q with that of zinc.
Your method should give valid results. [3]
To form silver metal during displacement reactions:
In reactions with a more reactive metal, the silver ions (Ag⁺) get displaced and form solid silver (Ag).[1]
Meausre the tempertaure change.[1]
when each metal is added to the silver nitrate solution.
The greater the temperature change, the more reactive the metal.[1]
The control variable is the same conecentartion of the solution.[1]
Reactivity of metals
A student is given three metals X,Y and Z.
The metals are magensium, iron and coppor.
They are added in a dilute hydrochoric solution .
One of the results show copper as unreactive
Mention iron and magensium and the control variable.[2]
Magnesium produces bubbles faster than iron.[1]
The control variable is the same concentration of hydrochloric acid.[1]
