53 terms

iGCSE Chemistry: Separating techniques - test yourself

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Define the term Saturated Solution
When no more solute can dissolve in a solution
Define the term Solute
The substance that dissolves in a solvent, forming a solution
Define the term Solution
The mixture of a soluble solute and a solvent
Define the term Solvent
The liquid which dissolves a solute
(Triple only) Define the term Solubility
A measure of how much solute dissolves in a solvent (in g per 100g)
(Triple only) What is the unit of solubility?
g of solute per 100g of solvent
(Triple only) A graph shows the solubility of sodium chloride in water at 50°C is 34g/100g. At that temperature, what mass of sodium chloride will dissolve in 200g water?
68g
(Triple only) A graph shows the solubility of sodium chloride in water at 50°C is 34g/100g. At that temperature, what mass of sodium chloride will dissolve in 50g water?
17g
(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
A substance is found to melt at a single, fixed melting point. Is it likely to be a pure substance or a mixture of substances?
Pure
A substance is found to melt over a range of temperatures. Is it a pure substance or a mixture of substances?
Mixture
Describe how pure salt can be obtained from rock salt
1) Grind rock salt into a fine powder. 2) Add powder to hot water and stir to dissolve salt. 3) Filter mixture. Salt solution passes through the filter paper leaving behind the sand. 4) Boil filtrate to evaporate some of the water. 5) Leave saturated solution to cool so that crystals of salt form. 6) Filter cold mixture to separate the crystals from the remaining solution.
Draw a beaker
Draw a conical flask
Draw a diagram to show equipment used in simple distillation
Draw a funnel
Draw a mass balance
Draw a measuring cylinder
Draw a test/boiling tube
Draw a thermometer
Draw a tripod
Draw an evaporating basin
Draw the equipment used in fractional distillation in the lab
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
State the method used to extract the red dye from a sample of rose petals
dissolving
State the method used to obtain kerosene from crude oil
fractional distillation
State the method used to obtain red food dye from a mixture of food dyes
paper chromatography
State the method used to obtain sand from a mixture of sand and water
filtration
State the method used to obtain solid copper sulfate from aqueous copper sulfate
crystallisation
State the method used to obtain water from salt water
simple distillation
Explain how a chromatogram shows that different dyes are different from each other
Each dye has components which rise to a different height on the paper
In paper chromatography if several dyes rise up the paper, why might another dyes not rise?
The other dye is insoluble in the solvent being used
In chromatography, what are the minimum and maximum possible values for an Rf value?
Minimum=0. Maximum=1.
What is the formula for calculating an Rf value?
Distance the dye has travelled divided by distance the solvent front has travelled. Both measured from the baseline.
In a paper chromatography experiment using a flammable solvent, why might a lid be used? (2)
To prevent the solvent from evaporating, and to reduce the risk of the solvent catching fire
In paper chromatography, the paper is position so it touches the solvent, but why is the paper position so baseline onto which dyes are placed is above the solvent?
So the dyes don't simply dissolve into the solvent
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.
Balance the equation for the reaction: ___ HCl(aq) + ___ MnO₂(s) → ___MnCl₂(aq) + ___H₂O(l) + ___ Cl₂(g)
4 HCl(aq) + MnO₂(s) → MnCl₂(aq) + 2H₂O(l) + Cl₂(g)
Balance the following equation: WO₃ + H₂ → W + H₂O
WO₃ + 3H₂ → W + 3H₂O
What do each of the following state symbols represent: (s), (l), (g), (aq)
(s) - solid. (l) - liquid. (g) - gas. (aq) - aqueous (in solution)
Can a base neutralise an acid?
Yes
What is a base?
A substance which can neutralise an acid, forming salt and water only
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
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
What happens to the rate of reaction if the temperature is INCREASED?
Rate of reaction increases dramatically
What simple change could be made to a reaction to speed it up dramatically?
Heat it up