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iGCSE Chemistry: Specification Experiments
Terms in this set (92)
Gas particles move at a speed of several hundred metres per second at room temperature. Explain why gases take several minutes to diffuse across a room
Gas particles collide with air particles and move in random directions
State and explain how increasing temperature affects the diffusion of a gas
Gas diffuses quicker because particles have more energy.
What name is given to the movement of gases?
(Triple only) State 2 ways in which more solute could be dissolved in a saturated solution
Heat the solution. Add more solvent.
(Triple only) What observation would be made if a saturated solution is cooled?
Solid would come out of solution
Draw a conical flask
Draw a diagram to show equipment used in simple distillation
Draw a funnel
Draw a mass balance
Draw an evaporating basin
Explain how fractional distillation is used to separate a mixture of different liquids
The different liquids have different boiling points
For what is the process of filtration used?
To separate an insoluble solid from a liquid
For what is the process of fractional distillation used?
To separate a mixture of different liquids that have different boiling points
For what is the process of simple distillation used?
To separate a liquid from a solution
For what is the separation technique of crystallisation used?
To obtain a dissolved salt from a salt solution
For what is the separation technique of paper chromatography used?
To separate various dyes from a mixture of dissolved dyes
In paper chromatography, why is the baseline drawn in pencil?
Pencil will not dissolve in the solvent, but if ink were used instead it might dissolve and interfere with the results of the chromatography.
State the steps for calculating empirical formula
1) mass/Aᵣ. 2) divide by the smallest. 3) Give the ratio has a whole number. 4) State final empirial formula
To determine the formula of a metal oxide by combustion, magnesium is heated in a crucible. Why is the crucible is cooled, weighed, reheated, cooled, re-weighed, and so on?
To make sure a constant mass has been reached and there is no more magnesium left to react
(Triple only) Explain what is meant by electrolysis
The breakdown of a substance using electricity
(Triple only) How could you determine if a liquid is an electrolyte?
Put it in a circuit including a bulb. If the bulb lights then the liquid is an electrolyte
(Triple only) Name the product formed at the anode during the electrolysis of molten copper chloride
(Triple only) Name the product formed at the cathode during the electrolysis of water
(Triple only) What is the name for the negative electrode?
(Triple only) What is the name for the positive electrode?
(Triple only) What type of reaction takes place at the anode?
(Triple only) What type of reaction takes place at the cathode?
(Triple only) Draw an electrolysis cell used to investigate the electrolysis of aqueous solutions
Describe how reactivity changes as you descend group 7
Hydrogen bromide is reacted with chlorine to form bromine. Write a chemical equation.
2HBr + Cl₂ → 2HCl + Br₂
In halogen displacement reactions, electrons are transferred from one atom to another. What type of reaction is this?
Draw a gas syringe
How can metal carbonates be used to produce carbon dioxide?
Themal Decomposition: when metal carbonates are heated, they break down releasing carbon dioxide. Alternatively, the carbonate can be added to an acid.
Describe a way in which the rusting of iron could be used to show the approximate percentage of oxygen in air
An excess of wet iron filings in left in a closed system with a known volume of air. After several days the volume of air has fallen as the oxygen is used up. The percentage of oxygen in air is calculates as the change in volume of gas divided by the initial volume (x100%)
Write the word equation to represent the reaction between sulfuric acid and magnesium
sulfuric acid + magnesium → magnesium sulfate + hydrogen
(Triple only) Describe how to carry out an acid-alkali titration
1) Pipette 25cm³ of alkali into a conical flask. 2) Add indicator. 3) Fill a burette with acid, record the initial volume. 4) Whilst swirling the flask, add the acid dropwise until the indicator changes colour. 5) Record the volume and calculate the volume of acid which was added. 6) Repeat until two concordant results (within 0.2cm³ of each other). 7) Result is the average of all concordant results.
(Triple only) Draw a burette
(Triple only) Draw a pipette
acid + alkali →
acid + alkali → salt + water
acid + base →
acid + base → salt + water
acid + metal →
acid + metal → salt + hydrogen
acid + metal carbonate →
acid + metal carbonate → salt + carbon dioxide + water
Describe the observations of the reaction of aluminium and dilute hydrochloric acid
fizzing and metal disappears
Give the formula of sulfuric acid
What two observations can be made when a metal reacts with an acid?
Bubbles. Metal disappears.
(Triple only) A pure, dry sample of a soluble salt can be prepared starting from an acid and alkali. What are the two stages of this method called?
Titration then crystallisation
(Triple only) Describe the method to prepare a pure dry sample of sodium chloride (soluble salt)
1) Pipette 25cm³ of sodium hydroxide into a conical flask. 2) Do not add indicator. 3) (Using titration values)Titrate the known volume hydrochloric acid into conical flask containing alkali. 4) Transfer to an evaporating basin. 5) Heat the solution until a hot saturated solution forms. 6) Allow the solution to cool so that hydrated crystals form. 7) Remove the crystals by filtration and wash with distilled water. 8) Dry by leaving in a warm place.
(Triple only) A pure, dry sample of an insoluble salt can be prepared starting with two soluble reactants. What is this method called?
(Triple only) Describe an experiment to prepare a pure, dry sample of an insoluble salt, starting from two soluble reactants
1) Mix the two salt solutions together in a beaker. 2) Stir with glass rod. 3) Filter using filter paper and funnel. 4) Wash with distilled water. 5) Dry by leaving in a warm place.
When preparing hydrated copper(II) sulfate crystals starting from copper(II) oxide, why is an excess of copper (II) oxide added?
To ensure all the acid has reacted so there is no acid left
When preparing hydrated copper(II) sulfate crystals starting from copper(II) oxide, why is the acid gently heated?
To speed up the reaction
(Triple only) What method would be followed to prepare a sample of pure, dry lead (II) sulfate?
A gas is bubbled through limewater and the limewater goes cloudy. Identify the gas.
Describe the test for ammonia gas
Turns damp red litmus paper blue
Describe the test for carbon dioxide gas
Bubble the gas through limewater and see if it goes cloudy
Describe the test for chlorine gas
Turns moist litmus paper white (bleaches)
Describe the test for hydrogen gas
Use a lit splint to see if the gas pops
Describe the test for oxygen gas
Use a glowing splint and see if it relights
Describe how you would carry out a flame test
Put solid onto a wire. Put into a blue flame
In a flame test, a blue-green colour is seen. Give the formula of the cation which is present.
In a flame test, a orange-red colour is seen. Give the formula of the cation which is present.
In a flame test, a red colour is seen. Give the formula of the cation which is present.
In a flame test, a lilac colour is seen. Give the formula of the cation which is present.
In a flame test, a yellow colour is seen. Give the formula of the cation which is present.
What is the test for copper (II) ions (Cu²⁺) and what is the result?
Add NaOH. A blue precipitate forms.
What is the test for iron (II) ions (Fe²⁺) and what is the result?
Add NaOH. A green precipitate forms.
What is the test for iron (III) ions (Fe³⁺) and what is the result?
Add NaOH. A brown precipitate forms.
What is the test for NH₄⁺ ions and what is the result?
Add NaOH. The gas (ammonia) turns damp red litmus paper blue.
Describe how you would test for carbonate ions (CO₃²⁻) and what is the result if they are present?
Add nitric acid and see if carbon dioxide bubbles form
Describe how you would test for sulfate ions (SO₄²⁻) and what is the result if they are present?
Add dilute HCl, followed by barium chloride (BaCl₂) and see if a white precipitate forms
When testing for halide ions, after silver nitrate is added to a sample a cream precipitate is formed. Give the formula of the anion present in the sample.
When testing for halide ions, after silver nitrate is added to a sample a white precipitate is formed. Give the formula of the anion present in the sample.
When testing for halide ions, after silver nitrate is added to a sample a yellow precipitate is formed. Give the formula of the anion present in the sample.
When testing for halide or sulfate ions, why is acid added added first?
To remove any carbonate ions
Describe the chemical test for water
Add it to anhydrous copper(II) sulfate which will change from white to blue if water is present
Describe a test to show whether water is pure
Heat the sample and measure the temperature. If the sample is pure water it will boil at 100⁰C
Explain why experimental values of enthalpy change differ from theoretical values
Heat energy is lost to the surroundings. Not all the reactants are used up.
Are combustion reactions exothermic or endothermic?
Are displacement reactions exothermic or endothermic?
Are neutralisation reactions exothermic or endothermic?
When a solid dissolves, is this process exothermic or endothermic?
Draw a diagram to explain that a catalyst provides an alternative pathway with lower activation energy.
Give a simple reaction can be used to investigate the effect of changing concentration on the rate of reaction
Marble chips added to hydrochloric acid of various concentrations
Describe the laboratory preparation of oxygen from hydrogen peroxide
Hydrogen peroxide is added to a flask containing a catalyst of manganese oxide, MnO₂. Oxygen is produced and is collected underwater.
State the catalyst used for making oxygen through the decomposition of hydrogen peroxide
Manganese (IV) oxide, MnO₂
Write the chemical equation for the decompostion of hydrogen peroxide, H₂O₂
2H₂O₂ → 2H₂O + O₂
State the colour change in the reaction of an alkene with bromine water
Orange to colourless
What is produced when an alkene reacts with bromine?
(Triple only) Ethanol is a flammable liquid. Suggest how it could be heated safely
Use a water bath
(Triple only) Name 3 ways in which ethanol can be oxidised
1) Burning in air or oxygen (complete combustion). 2) Reaction with oxygen in the air to form ethanoic acid (microbial oxidation). 3) Heating with potassium dichromate(VI) in dilute sulfuric acid to form ethanoic acid
(Triple only) A few drops of what should be added to ethanoic acid and ethanol to produce ethyl ethanoate?
Concentrated sulfuric acid
(Triple only) What type of reaction is esterification (the making of an ester)?
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