Inorganic chem and periodic table - Topic 4 Flashcards
what is thermal decomposition
the name of a reaction in which a compound decomposes on heating
what do acids and metals make
hydrogen gas and a salt (a metal compound)
what do acids and bases make (neutralisation reaction)
salt and water
why do all the reactions between acids and bases make water
as the hydrogen ions react with the hydroxide ions to form water
supporting equation
OH-(aq) + H+(aq) ——> H20
what do acids and carbonates make
salt water and carbon dioxide
solubility table
to revise this better draw a table with one side being what is soluble in water and the other being whats insoluble in water
what are soluble:
- all acids
- calcium, sodium and potassium hydroxide - HOWEVER OTHER METAL OXIDES AND HYDROXIDES ARE INSOLUBLE (NOT SOLUBLE)
- carbonates of sodium and potassium -HOWEVER ALL OTHER CARBONATES ARE INSOLUBLE (NOT SOLUBLE)
- all nitrates
- all chlorides - HOWEVER SILVER CHLORIDE AND LEAD CHLORIDE ARE INSOLUBLE (NOT SOLUBLE)
- all sulfates - HOWEVER BARIUM SULFATE AND LEAD SULFATE ARE INSOLUBLE (NOT SOLUBLE)
- all sodium, potassium and ammonium salts
what does the solubility table explain
if the compound is soluble in wate then it is an aqueous but if it isnt then it is a solid
What happens in reactions with alkali metals and water
- they all form metal hydroxides and hydrogen
- lithium gives off steam with bubbles of hydrogen
- sodium melts to form a shiny bead that skates on the surface of the water
- potassium catches on fire and burns with a lilac flame
Reactions with metals and chlorines
the all form colourless ionic metal chlorides
what is the trend of solubility down metal hydroxides
the solubility increases as you go down a group
why are hydroxides strong bases
as they are fully ionised in water, giving solutions of hydroxide ions
why do carbonates produce alkaline solutions when dissolved in water
as the carbonate ions remove the h+ ions from water molecules to form hydrogencarbonate ions and hydroxide ions, and these hydroxide ions make the solution alkaline
In a chemical test what proves the presence of hydroxides
white solids
In a chemical test what would group 1 nitrates look like
white crystalline solids
what does the thermal decomposition of group 1 NITRATE form AND whats the exception
a NITRITE and oxygen
e.g
2KNO3 —–> 2KNO2(s) + O2 (g)
EXCEPT LITHIUM as it decomposes into the oxide, nitrogen dioxide and oxygen
explain why sodium and potassium are used as chemical reagents
- their ions are inert so act as spectator ions
- they are the most soluble in water, including their hydroxides and carbonates compared to to other metal hydroxides and carbonates which are insoluble
- they are colourless in aqueous solutions so do not interfere with other colour changes
flame colours of GROUP 1 METALS
lithium - bright red
sodium - bright yellow
potassium - lilac
why does compounds containing sodium not burn during a flame test
as the energy from the flame excites the outer electrons of the sodium ions, raising them to higher energy levels, the atom emits the wavelength of a yellow light as as the electrons drop back to lower energy levels
Trend of solubility in group 2
Decreases as you go down the group
Why does the reactivity increase as you go down alkaline earth metals (group 2)
As the first and second ionisation energy decreases as the atomic radius increases and the number of inner electron shells increase as you go down the group, so there is a weaker attraction between the nucleus and outer electrons as you go down the group so the first and second ionisation energies decrease as less energy is required to remove the outer 2 electrons causing the reactivity to increase
How does Mg, Ca and Ba react with oxygen
- They all form a white ionic oxide (which are solids)
- Mg burns with oxygen to form a bright white flame and a white solid magnesium oxide
- calcium burns with a yellow flame and forms a white solid calcium oxide
- barium burns with a green flame to form a peroxide BaO2 (which is also white)
How do alkaline earth metals (group 2 metals) react with water and explain the trend in reactivity with water
- produces the alkaline metal hydroxides and hydrogen gas
- the rate of reaction increases as you go down the group as shileding and atomic radius increases, so electrons are further away from the nucleus, so easier to remove the two valence electrons
Why does the thermal stability of group 2 carbonates and nitrates increases as you go down the group
- as you go down the group the atomic radius of the metal ion increases, causing the size of the metal ion to increase so it will have a lower charge density,
- this decreases the polarising power of the metal ion as the low charge density makes it harder for the metal ion to attract the bonding electrons in carbonate/nitrate ion,
- so the electron cloud is not easily distorted so the bonds require a higher temperature to break so thermal stability increasees.
what is a basic oxide
a metal oxide which can react to form salts and water by acting as a base by taking the hydrogen ion from the base
what do group 2 metals and acids form
salt and water
as the group 2 metals are basic oxides
What do group 2 metal oxides and water form
A metal hydroxide
Explain the reaction of calcium oxide and water
the calcium oxide dissolves in the water to form calcium hydroxide solution but as calcium hydroxide is only slightly soluble in water so the solution becomes quickly saturated and as we continue to form calcium hydroxide this no longer dissolved but instead forms solid calcium hydroxide
Trend in solubility of group 2 hydroxides
Increases as you go down the group
How does the trend in solubility in group 2 hydroxides explain why group 2 metal hydroxides become more alkaline as you go down the group
As when the metal hydroxide dissolved in water it forms a metal ion and a hydroxide ion. This means that as the solubility increases down the group it will become more alkaline as the metal hydroxides will dissolve in water more easily (since solubility increases) and hence release more hydroxide ions making it more alkaline
Uses of group 2 hydroxides
- neutralisation reactions in agriculture and medicine
- treat indigestion ( the excess of HCL in the stomach) - such as milk of magnesia which contains Mg(OH)2
properties of group 2 sulfates
- similar in that they are all colourless solids with the formula MS04
- different in that they become less soluble down the group
properties of group 2 nitrates
- similar in that they all have the formula M(NO3)2 they are colourless crystalline solids, very soluble solids and decompose to the oxide when heated
- different in that they become more difficult to decompose down the group
general formula for the decomposition of group 2 nitrates
XNO3 —-> XO + NO2 + O2
lithium nitrate also follows this general formula
general formula for the decomposition of group 1 nitrates
2XNO3 —-> 2XNO2 + O2
EXCEPT LITHIUM - DOES NOT FOLLOW TGIS FORMULA
properties of group 2 carbonates
- similarities: they all have the formula MCO3, are insoluble in water, react with dilute acids and form an oxide and carbon dioxide during thermal decomposition
- differences: thermal stability increases down a group (become more difficult to decompose down the group)
general formula for the thermal decomposition of group 2 carbonates
XCO3 —-> XO + CO2
flame colours for group 2
beryllium - no colour
magnesium - no colour
calcium - brick red
strontium - bright red
barium - pale green
Colours of halogens at rtp
Florine - pale yellow gas
Chlorine - pale green gas
Bromine - red brown liquid
Iodine - grey black solid
Why does the melting point and boiling point increase as you go down group 7
As you go down the group the strength of the London forces increase as the number of electrons increase, so more energy is required to overcome the London forces as you go down the group so mp and bp increase down group 7 (that’s why the physical state goes from gas (F) to solid (I)
Explain the Trends in Electronegativity in the halogens
The Electronegativity decreases as you go down the group as the number of electron shells and atomic radius increases, which reduces the attraction between the bonding electrons and the nucleus causing the Electronegativity to decrease as you go down the group
What forms when a halogen reacts with a metal
Ionic halides
Explain the Trend in strength of oxidising agents in halogens
The strength of the oxidising agent decreases as you go down the group as the atomic radius increases as you go down the group and the number I’d shells also increase so the outer electrons become further from the nucleus and the attraction between the outer electrons and the nucleus decreases, making it harder for the halogens to gain an electron and hence act as a less powerful oxidising agent
Why can’t iron(111) iodine ions form when reacting iodine with iron
As the iodine ions reduce iron (111) to iron (11) ions. So when heating iron with iodine vapour it produces iron (11) iodide
test to distinguish halides and the result for the test
silver nitrate
add silver nitrate to a solution of halide ions to form a silver halide
- silver chloride - white precipitate, which turns purple grey in sunlight
- silver bromide - creamy coloured precipitate
- silver iodide - yellow precipitate
How does chlorine Bromine and Iodine react with hydrogen
- hydrogen Produces the colourless acidic gas, hydrogen chloride, HCL (NOT HYDROCHLORIC ACID only referred to hydrochloric acid when the gas is in a solution of water)
- bromine forms hydrogen bromide with a pale bluish flame
- iodine forms hydrogen iodide and unlike the other two it is a reversible reaction
Explain the Trend of the strength of reducing agents in halogens
The strength of reducing agents of halide ions increase as you go down the group as when you go down the group the atomic radius and the number of inner shields increase so the outer electron is further away frown the group so the attraction between the outer electron and the nucleus decreases making it easier for the halogens to lose an electron causing them to be a stronger reducing agent as you go down the group
Products from Reaction between sodium chloride and concentrated sulfuric acid and what type of reaction
NaCl (s) + H2SO4 (l) ——> NaHSO4 (s) + HCl (g)
Products: sodium hydrogensulfate (white solid) and hydrogen chloride (not hydrochloricacid) (forms white fumes)
Type of reaction: acid base reaction - as oxidation’s numbers stay the same and chloride ion is a weak reducing agent so cannot reduce the sulfur in the sulfuric acid
products formed from Reaction between sodium bromide and concentrated sulfuric acid and type of reaction and observations
2Br- + H2SO4(l) + 2H+ —-> SO2(g) + 2H2O(l) + Br2(l)
Products: sulfur dioxide gas, bromine and water
Observation: produces orange vapour (Br2) mixed with colourless acidified gas (SO2)
Type of reaction: redox
observation of precipitate formed when dissolving silver halides in aqueous ammonia
silver chloride - precipitate dissolves easily in DILUTE ammonia to form a colourless solution
silver bromide - precipitate dissolves n CONCETRATED aqueous ammonia to form colourless solution
silver iodide - precipitate does not dissolve in ammonia solution
Reaction between sodium iodide and concentrated sulfuric acid - observations, products and type of reaction
Products: iodine, sulfur and hydrogen sulfide
Observations : dark solid which gives of purple vapour (I2), yellow solid (S) and a bad egg smell (H2S)
Type of reaction: redox
Properties of hydrogen halide
- colourless gas at room temp which fume in moist air
- very soluble in water forming acidic solutions which completely ionise in water
- strong acids so ionise in water
Test for hydrogen halides
Mixing any hydrogen halide with ammonia will produce a white smoke of ammonium salt
E.g
Nh3 + HCl ——> NH4Cl
What happens when chlorine dissolves in water
A reversible reaction takes place to produce a mixture of hydrochloric acid and chloric(I) acid (hypochlorous acid)
Cl2 (g) + H2O (l) —-> HClO (aq) + HCl (aq)
<—– (REVERSIBLE REACTION)
state an application for the reaction between chlorine and water to make chloric (1) acid
To kill bacteria in drinking water
State an application for the reaction between sodium hydroxide to make sodium chlorate (same reaction with potassium but with sodium)
household bleach
what happens when chlorine is added to water in the presence of bright sunlight
- chlorine reacts with water to form hypochlorus acid which further breaks down into hydrogen chloride and oxygen gas by sunlight
Cl2 + H20 —-> HOCl + HCl
2HOCl ——> 2HCl + O2 (in the presence of sunlight)
overall equation: 2H20 + 2Cl2 ——-> 4HCL + O2
Trend of solubility in group 2 hydroxides and sulfates
Group 2 hydroxides - solubility increases down the group
Group 2 sulfates - solubility decreases down the group
Why do we dip the flame test wire into concentrated HCl
- it reacts with the compounds to form volatile chlorides
Why do metal ions produce different flame colours
As different wavelengths of light are released due to different gaps between energy levels
What is the flame test wire made from
Nichrome or platinum
Test for sulfate ions
You first acidify the solution you are testing with dilute hydrochloric acid and then add barium chloride solution.
If you have a sulfate, you will get a white precipitate of insoluble barium sulfate
Describe how you would compare the thermal stability of two different group 2 nitrates. You must include one safety precaution
- Record time it takes to produce a brown fume
- same heat applied
- same amount if each nitrate I’m seperate test tubes
- saftey precaution: fume cupboard
Explain the origins of flame colours
Heat from the flame promotes the electrons to higher energy levels, the electrons then drop back down to lower energy levels causing light to be emitted
write the half equation for the oxidation of the chlorine molecules to chlorate ions in the presence of cold hydroxide ions
Cl2(g) + 2OH- (aq) —–> ClO- (aq) + Cl- (aq) + H20 (l)
The reaction between chlorine and cold dilute sodium hydroxide solution
2NaOH + Cl2 ——> NaCl + NaClO + H2O
The reaction between chlorine and HOT concentrated sodium hydroxide solution
3Cl2+ 6NaOH ——-> 5NaCl + NaClO3 + 3H2O
Explain why magnesium nitrate, Mg(NO3)2 decomposes more readily on heating than potassium nitrate, KNO3
- magnesium ion is smaller (than the potassium ion)
- magnesium ion has a higher charge
- magnesium ion polarises nitrate ion more
- so weakening the N−O bonds more
A student suggest that the difference in the rates of reaction of strontium and barium with water is due to the difference in the sum of their first and second ionisation energies. Discuss this suggestion.
- The sum of the first two ionisation energies for barium is lower / barium loses (its outer) electrons more easily.
- Barium is a bigger atom/barium has a larger atomic radii
- Barium has greater shielding than Sr
- These outweigh the fact that Barium has more protons.
- Therefore Barium is more reactive.
ionic equation for the reduction of chlorine molecules to chloride ions
Cl2 +2e- ——> 2Cl-
All sodium halide reactions with concentrated sulfuric acid
Sodium chloride + concentrated sulfuric acid
Sodium bromide + concentrated sulfuric acid
Sodium iodide + concentrated sulfuric acid
Equation for the disproportionate reaction from chlorate (1) ions to chlorate (v) and chloride ions on heating
3ClO- (aq) ——> ClO3- (aq) + 2Cl- (aq)
How does Mg react with water
it reads slowly with water (but vigorously with steam) and produces MgO instead of MgOH
write out nitrate and nitrite formula
nitrATE - NO3-
nitrITE - NO2-
test for oxygen
test to see if gas RELIGHTS a GLOWING splint
how to see the colour change during halogen displacement
- add hexane (organic solvent)
- halogen will dissolve in organic solvent which will form a colour band above the aqueous layer
Displacement reactions with chlorine water, bromine water and iodine solution with potassium chloride, potassium bromide and potassium iodide
draw a table with potassium halides at the top and the Cl water, bromine water and iodide solution at the bottom
aqueous layer - layer at the bottom
organic layer - layer at the top (coloured band)
KCl + KBr + KI — colourless
chlorine water (colourless) and:
KCl - no reaction, aqueous layer - colourless, organic layer - colourless
KBr - Cl2 + 2Br- –> 2Cl- + Br2, aqueous layer - yellow, organic layer - orange
KI - Cl2 + 2I- –> 2Cl- + I2, aqueous layer - brown, organic layer - purple
bromine water (orange) and:
KCl - No reaction aqueous layer - yellow, organic layer - orange
KBr - No reaction aqueous layer - yellow, organic layer - orange
KI - Br2 + 2I- –> I2 + 2Br-aqueous layer - brown, organic layer - purple
bromine water (orange) and:
KCl - No reaction aqueous layer - brown, organic layer - purple
KBr - No reaction aqueous layer - brown, organic layer - purple
KI - No reaction aqueous layer - brown, organic layer - purple
