Elements of the sea Flashcards
Are nitrates & ethanoates soluble or insoluble?
All soluble
Are sulphates all soluble/insoluble and what are the exceptions
All soluble except from- Ba, Pb and Ca
Are halides soluble/insoluble and what are the exceptions?
All soluble apart from- Ag and Pb
Are carbonates soluble/insoluble and what are the exceptions?
All are insoluble apart from - Na, K and NH4
Are hydroxides soluble/insoluble and what are the exceptions?
All insoluble except from- Li, Na, K and Ca (sparingly soluble)
Are oxides soluble/ insoluble and what are the exceptions?
All insoluble (Gp1 and 2 react with water to produce hydroxides)
Write the ionic equation for:
Hydrochloric acid + sodium hydroxide —- sodium chloride + water
H+ + OH- —h20
What are the two mains way to prepare soluble salts
Titration = acid + alkali
Acid + insoluble base= crystallisation
How to test for insoluble salts
Precipitation reactions
Deduce the oxidation numbers of each element in these compounds:
LiAlH4
Na2O2
NaclO4
Li -+1
Al- +3
H- -1
Na - +1
O- -1
Na- +1
Cl- +7
O- -2
What is oxidation and reduction in redox reactions
Oxidation= gain of oxygen and loss of electrons (increase in oxidation number)
Reduction= loss of oxygen and gain of electrons (decrease in oxidation number)
What is an oxidising agent?
An element or compound that has caused the oxidation of another, it accepts electrons so therefore is reduced.
What is a reducing agent?
An element or compound that causes the reduction of another, it looses electrons and therefore is oxidised.
Define electronegativity and state the most electronegative element
Electronegativity is a measure of the ability of an atom to attract the bonding pair electrons in a covalent to itself.
The most electronegative atom is Fluorine.
State three physical properties of halogens
. Low melting and boiling points increases down group- increase in strength of intermolecular bonds
. Less volatile down the group
. solubility- non-polar molecules dissolve better in non-polar solvents
State the colour and state ofF2, Cl2, Br2 and I2 at rtp.
F2- very pale yellow gas
Cl2- pale green gas
Br2- brown/red liquid
I2- shiny grey solid
State the colour of Cl2, Br2 and I2 at non-polar solvents and water
Cl2- pale green, very pale green
Br2- orange, yellow/orange
I2- purple, brown/yellow
State chemical properties of redox reactions in general
. Halogens are oxidising agents so are reduced and oxidising strength decreases down the group
. Halide ions are reducing agents so are oxidised and reducing strength increases down group
Describe the method to react halogens with halide ions (redox)
- Mix solution of halogen with halide ions
- add organic (non-polar0 solvent (cyclohexane) and shake
- The layers should separate
- The upper layer will be the halogen dissolved in the organic solvent
- use the colour as identification
State the test for halide ions
- acidify with HNO3
- add aqueous AgNO3
- Observe the colour of the precipitate
- Add NH3 solution and shake
State the four properties of hydrogen halides
- covalent molecules
- dissolve in water forms acidic solutions
- Halide ions act as reducing agent
- Reducing strength increases down the group
Observation and equation of Sodium fluoride and sodium chloride
Observation: misty fumes of HF or HCL
Naf + H2SO4 -NaHSO4 + Hf
Nacl +H2SO4 -NaHSO4 +HCL
Observation of NaBr and sulfuric acid and equation
Observation: Misty fumes of HBR and brown fumes (Br2)
2HBr + H2SO4 – SO2 + Br2 + 2H2O
Reaction of NaI with sulfuric acid observation and equation
Observation: Misty fumes (HI) and a rotten egg smell
8HI + H2SO4– H2S + 4I2 + 4H2O
What can be used as an alternative from sulfuric acid when reacted with hydrogen halides?
Phosphoric acid
What happens at the anode?
Negative anions move towards the anode.
Negative ions lose electrons forming atoms (oxidised).
What happens at the cathode.
Positive cations more towards cathode.
Positive ions gain electrons forming (reduced).
State three properties of dynamic equilibrium
- rates of forwards= rates of backwards reaction
- concentrations of reactants and products remains constant
- only exists in closed systems
What is Le Chatelier’s principle?
The position of equilibrium will shift so as to minimise the effect of any change in conditions.
Summarise the effect of temperature on equilibrium
If forwards is exothermic= an increase of temp will shift it to left, decrease in temp will shift to right
If forwards is endothermic=
an increase in temp will shift to right, decrease in temp will shift left
Summarise the effect of pressure on equilibrium
If forwards produces more moles of gas: shifts to left with less moles when increased pressure, decreased pressure will shift to right with more moles
Opposite if forward produces less moles.
How to test for carbonates
Add an acid and if there is effervescence then CO32- ions are present. To prove this bubble it through limewater and it’ll turn cloudy.
How to test for sulphate ions
Add nitric acid and barium nitrate solution. A white precipitate will form.
How to test for halide ions
Add nitric acid and silver nitrate then a coloured precipitate will determine which halide is present. Then add ammonia to determine further.
How to test for ammonium ions
Add sodium hydroxide and warm the mixture. Test it with red damp litmus paper and it’ll turn blue.
