53 terms

iGCSE Chemistry: Salts preparation - core

STUDY
PLAY
1.170 g of CoCl₂.xH₂O gave a residue of 0.641 g on heating. Find x.
6
7.485 g of a hydrated copper(II) sulphate CuSO₄.xH₂O was heated producing 4.785g of anhydrous copper(II) sulphate. What is the formula of the hydrated salt?
CuSO₄.5H₂O
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
What is the empirical formula of an alcohol with the analysis; 52.2% C, 13.0% H and 34.8% O?
C₂H₆O
What is the formula of a compound in which 0.48 g of carbon combines with 0.08 g of hydrogen and 0.64 g of oxygen?
CH₂O
Work out the empirical formula of an oxide of chlorine contains 7.1 g of chlorine and 1.6 g of oxygen.
Cl₂O
Is aluminium sulfate soluble?
yes
Is barium carbonate soluble?
no
Is barium sulfate soluble?
no
Is silver chloride soluble?
no
Is sodium sulfate soluble?
yes
State the solubility rule for carbonates salts
all carbonates are insoluble, except those of sodium, potassium and ammonium
State the solubility rule for chloride salts
all are soluble, except silver chloride
State the solubility rule for nitrate salts
all nitrates are soluble
State the solubility rule for sodium, potassium and ammonium salts
all common sodium, potassium and ammonium salts are soluble
State the solubility rule for sulfate salts
all sulfates are soluble, except those of barium and calcium
A pure, dry sample of a soluble salt can be prepared starting with an insoluble reactant. What is this method called?
Excess solid method
Describe the method to prepare a pure dry sample of copper sulfate (soluble salt)
1) Heat acid in a beaker. 2) Add base until excess and stir with glass rod. 3) Filter the mixture using filter paper and funnel. 4) Heat the filtered solution (filtrate) until a hot saturated solution forms. 5) Allow the solution to cool so that hydrated crystals form. 6) Remove the crystals by filtration and wash with distilled water. 7) Dry by leaving in a warm place.
(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 alkali into a conical flask. 2) Do not add indicator. 3) (Using titration values)Titrate the known volume 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?
Precipitation method
(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?
Precipitation method
A gas is bubbled through limewater and the limewater goes cloudy. Identify the gas.
Carbon dioxide
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, why is hydrochloric acid used?
To clean the wire of any unwanted ions
In a flame test, a blue-green colour is seen. Give the formula of the cation which is present.
Cu²⁺
In a flame test, a orange-red colour is seen. Give the formula of the cation which is present.
Ca²⁺
In a flame test, a red colour is seen. Give the formula of the cation which is present.
Li⁺
In a flame test, a lilac colour is seen. Give the formula of the cation which is present.
K⁺
In a flame test, a yellow colour is seen. Give the formula of the cation which is present.
Na⁺
How would you test for the ammonium ion (NH₄⁺)?
Add sodium hydroxide. If ammonium ions were present, ammonia gas will form which will turn damp red litmus paper blue
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). A white precipitate will form
Describe the test for bromide ions
Add dilute nitric acid and silver nitrate. A cream precipitate of silver bromide is formed.
When testing a sample for ions, hydrochloric acid and then barium chloride are added to a sample. A white precipitate forms. What is the name of that precipitate?
barium sulfate
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.
Br⁻
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.
Cl⁻
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.
I⁻
When testing for halide or sulfate ions, why is acid added added first?
to remove any carbonate ions
Which two substances are added when testing for halide ions, and what is the result if they are present?
Add dilute nitric acid and silver nitrate
Which two substances are added when testing for the sulfate (SO₄²⁻) ions? (2)
Add dilute HCl, followed by barium chloride (BaCl₂)
OTHER SETS BY THIS CREATOR