Topic 4: inorganic

What is the definition of first ionisation energy?
The energy required to remove of mole of electrons from one mole of an element the gaseous state.
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What is the definition of second ionisation energy?
The energy required to remove one mole of electrons from one mole of singly charged positive ions in the gaseous state.
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What are the three factors that affect ionisation energy?
Nuclear charge, Atomic radius and shielding.
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What is the trend in ionisation energy down group 2?
Ionisation energy decreases down the group, because although nuclear charge increases so does the atomic radius and shielding which outweigh nuclear charge.
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What is the general equation for first ionisation energy?
M(g) → M+(g) + e-
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What is the general equation for second ionisation energy?
M+(g) → M2+(g) + e-
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What is the trend in reactivity down group 2?
There is a general increase in reactivity down the group because the deceasing ionisation energies.
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What is the general equation for the reaction of group 2 metals with oxygen?
2M(s) + O2(g) → 2MO(s) (requires heat to start)
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What is the general equation for the reaction of group 2 metals and chlorine?
M(s) + Cl2(g) → MCl2(s) (requires heat to start)
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What is the general equation for the reaction of group 2 metals with water?
M(s) + 2H2O(l) → M(OH)2(aq) + H2(g)
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What is the equation for the reaction of magnesium with steam?
Mg(s) + H2O(g) → MgO(s) + H2(g)
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What happens to hydrogen gas produces in this reaction and why?
The hydrogen formed in burned as it leaves the tube to prevent it escaping into the laboratory as it is highly flammable.
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What can we predict and beryllium and radium?
Beryllium is less reactive that magnesium and radium is more reactive than barium.
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What are basic oxides?
Oxides of metals that react with water to form metal hydroxides, and with acids to form salt and water.
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What is the general equation for when group 2 oxide react with water?
MO(s) + H2O(l) → M(OH)2(aq)
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What is the ionic equation for the reaction of group 2 oxides and water?
O2- + H2O → 2OH- (the OH- ions show thats the resulting solution is alkaline)
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What is the trend of the solubility of group 2 hydroxides down the group?
The solubility of group 2 hydroxides increases down the group, which means that the alkalinity of the solutions forms increases down the group too.
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What is the test for carbon dioxide?
Bubble it through lime water (Ca(OH)2) and the limewater turns cloudy. This is because a precipitate of CaCO3 forms (as well as water) which makes the solution look cloudy.
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What is the equation for the reaction that occurs between carbon dioxide and lime water?
CO2 + Ca(OH)2 → CaCO3 + H2O
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What is milk of magnesia?
Milk of magnesia is magnesium hydroxide in water, which acts as an antacid.
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How does milk of magnesia stop indigestion?
Mg(OH)2 + 2HCl → MgCl2 + 2H2O , hydrochloric acid reacts with the magnesium hydroxide which relieves the symptoms of indigestion which are caused by too much acid.
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How does the low solubility of magnesium hydroxide allow it to be used as an antacid?
Because of its low solubility there aren't high concentrations of OH- ions (which attack human tissue) so it does not pose a risk to health.
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What is the general formula for the reaction of group 2 oxides with acids?
MO + 2HCl → MCl2 + H2O (or correct answer with a different acid)
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What is the general formula for the reaction of group 2 hydroxides with acids?
M(OH)2 + 2HCl → MCl2 + 2H2O
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What can slake lime be used for?
Slake lime is used to neutralise excess acidity in soil, the reaction is Ca(OH)2 + 2HNO3 → Ca(NO3)2 + H2O
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What is the trend in solubility of group 2 sulphates?
The solubility of group 2 sulphates decreases down the group.
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Are group 2 chlorides and nitrates soluble?
All group 2 nitrates and chlorides are soluble.
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What is the test for sulphate ions?
Add a solution of barium ions (barium chloride or nitrate). The sulphate ions will react with the barium ions and form a white precipitate of barium sulphate.
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What is the ionic equation for the test for sulphate ions using barium ions?
Ba2+(aq) + SO42-(aq) → BaSO4(s)
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How do you prevent white precipitates of other compounds forming?
There must be H+ ions present to prevent barium carbonate from forming as a white precipitate. so dilute nitric of hydrochloric acid is added as part of the test.
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What are barium meals and why are they used?
Barium meals contain barium sulphate, consuming it before an X-ray allows soft tissues to show up more clearly because it is a dense white solid.
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Why is it not an issue that barium sulphate contains barium ions, which are poisonous?
Because barium sulphate is insoluble, so although it contains barium ions they are not free to move so are not poisonous.
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What is the definition of thermal stability?
It is the measure of the extent to which a compound decomposes when heated.
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What are the factors that mean the decomposition of group 2 nitrates or carbonates if different to the melting of the group 1 chlorides?
The charge on the group 2 ions is double that of the group 1 ions, the atomic radius of group 2 cations is smaller that group 1 cations in the same period and the nitrate and carbonate ions are more complex than chlorine ions.
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What does the larger more complex nitrate ion mean in terms of decomposition?
Larger, more complex nitrate ions can change into smaller and more stable nitrite ions (NO2-) or oxide ions when heated by decomposing and producing oxygen or nitrogen dioxide gas.
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What does the larger, more complex carbonate ions mean in terms of decomposition?
The carbonate ion can change into the oxide ion by decomposing and releasing carbon dioxide gas.
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What influences the stability of the nitrate and carbonate ions?
The charge and size of the cations present affect their stability. Smaller and more highly charges cations polarise and change the anion more.
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What is the appearance of nitrogen dioxide?
Brown fumes
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What is the test for oxygen?
Relighting a glowing splint
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What trend occurs in the thermal stability of the group 2 nitrates?
There is a general increase in thermal stability down group 2, because beryllium is the smallest cation and so is the most polarising and they all have the same charge of 2+.
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Compare the thermal stability of group 1 and 2 nitrates.
Group 1 nitrates are more thermally stable than group 2 nitrates because they have a smaller charge and have bigger atomic radii in the same period, which makes them less polarising so more thermally stable.
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Which type of decomposition is likely to be present is no brown fumes are observed?
Lesser decomposition, the general equation is metal nitrate → metal nitrite + oxygen
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If brown fumes are observed which type of decomposition is likely?
Greater decomposition, the general equation is metal nitrate → metal oxide + nitrogen dioxide + oxygen
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What type of decomposition do all group 1 nitrates undergo except lithium?
Lesser decomposition
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What type of decomposition do all the group 2 nitrates and lithium nitrate undergo?
Greater decomposition
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What are the conditions for decomposition?
Heat the compound in a test tube
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What is the equation for the decomposition of lithium nitrate?
4LiNO3 → 2Li2O + 4NO2 + O2
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What is the equation for the decomposition of sodium nitrate?
2NaNO3 → 2NaNO2 + O2
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What is the equation for the decomposition of beryllium?
2Be(NO3)2 → 2BeO + 4NO2 + O2
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What state and colour are all group 1 and 2 nitrates and carbonates?
They are all white solids
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What is produced if the carbonate does decompose?
An oxide and carbon dioxide
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Can any observations be made?
No observations can be made as the gas given off is colourless and both carbonates and oxides are white solids. However the gas produced can be pumped through lime water and if it is carbon dioxide the lime water will go cloudy.
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What is the general equation for the decomposition of carbonates?
Metal carbonate → metal oxide + carbon dioxide
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What is the pattern in group 1 and 2 carbonate decomposition?
Like the nitrates the group 2 carbonates and lithium carbonate are less thermally stable, this means that they decompose more readily. So the group 1 carbonates do not tend to decompose but group 2 and lithium carbonates do.
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What is the equation for the decomposition of lithium carbonate?
Li2CO3 → Li2O + CO2
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What is the equation for the decomposition of calcium carbonate?
CaCO3 → CaO + CO2
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When does decomposition of carbonates happen?
When the cation has a 2+ charge or when the 1+ charged cation is the smallest in group 1 (lithium)
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Flame test colour of lithium
Red
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Flame test colour of sodium
Yellow/orange
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Flame test colour of potassium
Lilac
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Flame colour test of Rubidium
Red/purple
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Flame test colour of caesium
Blue/violet
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Flame test colour of beryllium
No colour
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Flam test colour of magnesium
No colour
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Flame test colour of calcium
Brick red
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Flam test colour of strontium
Crimson red
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Flame test colour of barium
Apple green
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First step of a flame test
Using a dropper add a few drops of concentrated hydrochloric acid to the solid and mix them so that the metal begins to dissolve.
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Why is it mixed with HCl?
To convert the metal into a metal chloride, which are more volatile that other salts so are more likely to give better results.
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What is the second step of a flame test?
Dip a clean platinum of nichrome wire into the mixture to obtain a sample of the compound.
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How is the wire cleaned?
The wire is placed in HCl and then placed in the flame until no other colours are present, then dipped in the hydrochloric acid again.
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What is the final step when carrying out a flame test?
Hold the end of the wire in the flame and observe the colour
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What are the two problems with flame tests?
Many compounds contain sodium compound impurities which have an intense colour and so can mask any colours produced by the metal itself. And describing colours is subjective.
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What is the Copper flame test colour?
Blue-green
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What causes the colour seen in flame tests?
The electrons of the compound absorb energy and move from their ground state to higher energy levels, referred to as the excited state.This is then followed by the return of the electrons to their ground state.
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Why does this show a colour?
The energy released corresponds to radiation in the visible spectrum, causing the colour. If no colour is seen then the the energy released is not in the visible spectrum.
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What is the test for ammonium ions?
Add sodium hydroxide and warm the mixture. The equation is: NH4+ + OH- → NH3 + H2O. Ammonia has a characteristic smell, but also turns damp red litmus paper blue.
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What is another way of testing for ammonia?
Hydrogen chloride gas reacts with ammonia to form white fumes of ammonium chloride. The equation for this reaction is: NH3 + HCl → NH4Cl
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What is fluorine like at room temperature and pressure?
Pale yellow gas
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What is chlorine like at room temperature and pressure?
Green/yellow gas
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What is bromine like at rom temperature and pressure?
Brown liquid
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What is iodine like at room temperature and pressure?
Purple solid but easily become a dark purple vapour
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What is astatine like at room temperature and pressure?
Black solid
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What are the trends in Melting and boiling points down group 7?
Melting and boiling point increase down group 7 because the forces between the atoms in the diatomic molecule have increasing strength.
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What is the equation for the sublimation of a halogen?
X2(s) → X2(g)
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What does the electronegativity of an atom depend on?
Its nuclear charge, atomic radius and shielding
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What is the trend in electronegativity down group 7?
electronegativity decreases down group 7
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What is the trend in reactivity down group 7?
reactivity decreases down group 7. because of their high electronegativity the halogens are good oxidising agents making them more reactive, this also means that fluorine is the most reactive as the most electronegative.
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Which reactions are most vigorous between group 1 and 2 and group 7?
Reactions between elements at the bottom of group 1 and 2 and elements at the top of group 7 are the most vigorous, this is explained by those being the most reactive elements in those groups.
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What are the products of reactions between group 1/2 metals and the halides?
They are salts which are usually white ionic solids
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What is disproportionation?
The simultaneous oxidation and reduction of an element in a single reaction.
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What are displacement reactions?
When one halogen replaces/displaces a less reactive halogen from its compound.
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How can displacement be observed?
Colour changes
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what colour is chlorine in cyclohexane?
pale green
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what colour is bromine in cyclohexane?
orange
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what colour is iodine in cyclohexane?
purple
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What is the formula of chloric acid?
HClO
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What is the equation for the reaction of chlorine with water?
Cl2 + H2O → HCl + HClO. This is a disproportionation reaction
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What is the equation for the reaction of chlorine with cold alkali?
Cl2 + 2NaOH → NaCl + NaClO + H2O. this is a disproportionation reaction
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What is the equation for the reaction of chlorine with hot alkali?
3Cl2 + 6NaOH → 5NaCl + NaClO3 + 3H2O. this is a disproportionation reaction
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What is the trend in oxidising power down group 7 of the halogens?
The oxidising power decreases down the group.
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What is the trend in the halide ions' reducing ability?
The reducing ability of the halide ions increases down the group.
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What is the general equation for the oxidation of the halide ions?
2X- → X2 + 2e-
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What is the equation for the partial ionisation of sulphuric acid?
H2SO4 H+ + HSO4-, Then: HSO4- H+ + SO42-
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Does sulphuric acid act as an oxidising or reducing agent?
It acts as an oxidising agent, so it is reduced
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What are the 3 possible reduction products?
Sulfur dioxide, sulphur and hydrogen sulfide. which of these is formed will depend on the species being oxidised.
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What is the first half equation for the reduction of sulphur?
H2SO4 + 2H+ + 2e- → 2H2O + SO2
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What are the oxidation states of sulphur in this equation?
In H2SO4 sulphurs oxidation state is +6, and in SO2 it is +4. So it has gained two electrons and so it reduced.
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What is the second half equation for the reduction of sulphur?
H2SO4 + 6H+ + 6e- → 4H2O + S
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What are the oxidation numbers of sulphur in this equation?
In H2SO4 sulfurs oxidation number is +6 and in S it is 0, so sulphur has gained 6 electrons and has been reduced further than in the first equation.
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What is the third half equation for the reduction of Sulphur?
H2SO4 + 8H+ + 8e- → 4H2O + H2S
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What are the oxidation numbers of sulphur in this equation?
In H2SO4 sulfurs oxidation number is +6 and in H2S it is -2
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What observations would be seen if concentrated sulphuric acid was added to NaCl?
Misty fumes (HCl)
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What observations would be seen if concentrated sulphuric acid was added to NaBr?
Misty fumes (HBr), brown fumes (Br2), colourless gas with a choking smell (SO2).
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What observations would be seen if concentrated sulphuric acid was added to NaI?
Misty fumes (HI), purple fumes or a black solid (I2), colourless gas with a choking smell (SO2), yellow solid (S), colourless gas with a rotten egg smell (H2S).
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What is the equation for the reaction of H2SO4 with NaCl?
NaCl + H2SO4 → NaHSO4 + HCl
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What is the overall equation for the reaction of H2SO4 and NaBr?
2HBr + H2SO4 → 2H2O + SO2 + Br2
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What is the overall equation for the reaction of H2SO4 an NaI?
6HI + H2SO4 → 4H2O + S + 3I2
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Why can't aqueous ammonia be used to detect fluoride ions?
Because silver fluoride is soluble.
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What colour precipitate do Iodide ions form with silver nitrate solution?
Yellow precipitate
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what colour precipitate do chloride ions with silver nitrate form?
White precipitate
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What colour precipitate do bromide ions form with silver nitrate solution?
cream precipitate
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If the silver halide is soluble in dilute aqueous ammonia then which of the halide is it?
Chloride ions
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If the silver halide is soluble in concentrated aqueous ammonia then which halide is present?
Bromide ions
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If the silver halide is not soluble in either then which halide is present?
Iodide ions
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What is the general equation for the formation of the silver halide precipitates?
Ag+(aq) + X-(aq) → AgX(s)
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What must be added to the silver nitrate solution and why?
Nitric acid, it reacts with any other anions present (like carbonates), as they would also form a precipitate.
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What are the hydrogen halides?
HX, they are colourless gases which exist as polar diatomic molecules. They can also act as acids.
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What do the hydrogen halides form when they react with water?
They form a acidic solution all of which are colourless
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What is the general equation for the reaction of the hydrogen halides and water?
HX + H2O → H3O+ + X- ( except for fluorine which is reversible because it is a weak acid)
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Other cards in this set

Card 2

Front

What is the definition of second ionisation energy?

Back

The energy required to remove one mole of electrons from one mole of singly charged positive ions in the gaseous state.

Card 3

Front

What are the three factors that affect ionisation energy?

Back

Preview of the front of card 3

Card 4

Front

What is the trend in ionisation energy down group 2?

Back

Preview of the front of card 4

Card 5

Front

What is the general equation for first ionisation energy?

Back

Preview of the front of card 5
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