Inorganic Chem and the Periodic Table Flashcards
What ions do Group 2 elements form when they react?
+2 ions
They lose 2 electrons and have electron configurations ending in s2
How does extra shells have an affect on the atomic radius?
Extra shells added as we go down group 2
The atomic radius increases as we go down group 2
What is the trend in ionisation energies in group 2 and explain why this happens
decreases
as the atomic radius increases and extra shells are added as we go down group 2, so the outer electrons are further from the nucleus and there is more shielding so there is a weaker attraction between the outer electrons and the nucleus
both of these make it easier to remove the outer electron and so less energy is needed to remove one
What do you use to test for halide ions?
Acidified AgNO3
Why does an increase in the number of protons, so therefore increase in + charge, not have an effect on ionisation energies?
The shielding effect overrides an increase in positive charge
When group 2 elements react with water to form?
What is the general equation for this?
bases
a reaction with water may form a metal hydroxide
M(s) + 2H2O(l) –> M(OH)2(aq) +H2(g)
What is the reactivity trend (with water) in group 2?
Which element react slowly and which element is the exception?
Be is the exception- since no reaction happens
Increases down the group
Mg- very slow
Be- exception
Explain the reasons for the trend in reactivity in group 2
Atom gets larger and electron is further from nucleus. Easier to remove and hence more reactive. There is more shielding
What happens when group 2 metals and cold water react?
they form metal oxides, group 2 metal oxides are white solids
What do group 2 elements form when they react with chlorine and what is the general equation for the reaction?
metal chlorides
M(s) + Cl2(g) –> MCl2(s)
What do group 2 oxides form when reacted with water
bases
Alkaline solutions
What is the trend in alkaline strength down group 2
They become more strongly alkaline as we go down the group as the hydroxides become more soluble.
What happens when oxides react with water
Oxides react readily with water to make hydroxides which dissociate to form OH- ions
What is the reaction like between
Magnesium oxide and water
Beryllium oxide and water
Magnesium oxide reacts very slowly and the hydroxide barely dissolves
Beryllium oxide doesn’t react with water at all and the hydroxide is insoluble
What is the general reaction between group 2 metals and HCl?
M(s) + 2HCl(aq) –> MgCl2(aq) +H2(g)
What is the general reaction between group 2 metals and H2SO4?
M(s) + H2SO4 __> MSO4(aq) + H2(g)
What is the type of reaction when group 2 oxides and hydroxides react with acids?
Neutralisation
If the anion has a single charge (e.g. hydroxides) what is the trend in solubility?
increasing
Mg(OH)2 is slightly soluble
Ba(OH)2 creates a strong alkaline solution
If the anion has a double charge (e.g. sulfates) what is the increase in solubility?
decreasing
BaSO4 is the least soluble
What is the equation for when carbonates break down via thermal decomposition?
MCO3(s) –> MO(s) + CO2(g)
What is the equation for when nitrates break down via thermal decomposition?
2M(NO3)2(s) –> 2MO(s) + 4NO2(g) + O2(g)
What is the trend in thermal stability in group 2 carbonates/ nitrates?
increases going down group 2
Explain the trend in thermal stability in group 2 carbonates?
Group 2 carbonates are more thermally stable as you go down the group
Cations get bigger so therefore have less of a polarising effect and distort the carbonate ion less
As the C-O bond is not weakened as it is much harder to break down
explain the reason for the trend of thermal stability in group 1 carbonates
group 1 carbonates do not decompose except for lithium
this is because they don’t have a big enough charge density to polarise the carbonate ion as they only form 1+ ions
however the lithium ion is small enough to have a polarising effect so therefore lithium carbonate can decompose
Which is more thermally stable group 1 compounds or group 2 compounds?
group 1
What happens when carbonates are under a Bunsen flame?
they are thermally stable
Give the equation for Lithium carbonate decomposing
Li2Co3 (s) –> Li2O(s) + CO2(g)
What do nitrates break down into?
nitrites and oxygen
What is the equation for KNO3 breaking down?
2KNO3(s) –> 2KNO2(s) + O2(g)
Give the formula for a nitrate ion
NO3-
Give the formula for a nitrite ion
NO2 3-
What are the two ways to test thermal stability for nitrates
1) measure how long it takes for a specific amount of oxygen to be produced. Use a gas syringe. Or relight a glowing splint
2) the length of time it takes until a specific amount of NO2 is produced.
What is the risk of using NO2
brown gas that is toxic
How would you test the thermal stability of a carbonate?
the length of time it takes until a specific amount of CO2 is produced. CO2 turns limewater cloudy so the quicker this turns cloudy, the more CO2 is produced. Could use a gas syringe
May also see fizzing
What is the method for conducting a flame test
Dip nichrome wire in concentrated HCl (to sterilise)
Dip it into the sample
Place the loop into the blue bunsen flame and observe the colour
what is the reason for the trend of thermal stability of group 2 nitrates
the ease of thermal decomposition decreases down group 2 and this is because down the group the ions get larger and therefore have less charge density
which means there is less polarisation of the nitrate anion and less weakening of the N-O bond
What are the flame test results/ colours for: Lithium Sodium Potassium Rubidium Caesium Magnesium Calcium Strontium Barium
crimson red orange-yellow lilac red blue No flame- energy emitted is outside visible spectrum brick red red apple green
How do we get different colours in flame tests?
Electrons in the shells move to higher energy levels as they absorb energy from the flame.
When they drop back down to lower energy levels, light is released.
Different colours are produced as the difference in energy levels determines the wavelength of light released
list 2 properties of the halogens
low melting and boiling points
exist as diatomic molecules
Describe the states of F, Cl, Br and I
F- pale yellow gas
Cl- pale green gas
Br- brown-orange liquid
I- grey solid but brown in water, and violet in cyclohexane
What can be added to make colour changes easier to see in halogen displacement reactions
Organic solvents, e.g. hexane
What happens between the halogen and organic solvent
halogen present will dissolve readily in the organic solvent which forms a layer above the aqueous layer- a coloured band will appear
What is the trend in reactivity for halogens?
decreases going down the group
Explain the trend in reactivity for the halogens
Atomic radius increases
Electron shielding increase
The ability to gain an electron and form 1- ions decreases
What is the trend in oxidising ability for halogens
Decreasing going down the group
Cl is the strongest and I is the weakest
Cl has the fewest occupied electron shells and the greatest force of attraction between outer electrons and the nucleus.
therefore is the easiest to gain electrons and be reduced, which makes it the best oxidising agent
How can we show the trend in oxidation for the halogens
reacting halogens with halide ions
What is formed when halogens react with group 1 and 2 metals
metal halides
What is the equation for a group 2 element + a halogen
M(s) + Cl2(g) –> MgCl2(s)
What is the equation for a group 1 element + a halogen
2M(s) + Cl2(g) –> 2LiCl(s)
What is the rule for fluorine’s oxidation state
can only be 0 or -1
What is the equation for a halogen reacting with a cold alkali
X2 + NaOH –> NaOX + NaX +H2O
What is the ionic equation for a halogen reacting with a cold alkali
X2 + 2OH- –> OX - + X- + H2O
What is the equation for a halogen reacting with a hot alkali
3X2 + 6NaOH –> NaOX3 + 5NaX + 3H2O
What is the ionic equation for a halogen reacting with a hot alkali
3X2 + 6OH- –> XO3- + 5X- +3H2O
How is bleach made?
Mixing chlorine and sodium hydroxide to form sodium chlorate (I) (bleach)
What is the equation for forming bleach?
2NaOH(aq) + Cl2(g) –> NaClO(aq) + NaCl(aq) +H2O(l)
Cold dilute alkali
what are three uses of sodium chlorate (I)
treating water
bleaching paper
as a cleaning agent
What does adding water to chlorine do?
produces chlorate (I) ions (ClO-) which will kill bacteria and make it safer to drink
What is the equation for water and chlorine reacting
H2O(l) + Cl2(g) HCl(g) + HClO(aq)
What is the equation for chloric acid and water reacting?
HClO(aq) + H2O(l) ClO- + H3O+(aq)
what is a common name given to group 2 metals?
alkaline earth metals
what is the most reactive group 2 metal
barium
what are 3 physical properties of group 2 metals
high melting and boiling points
low density metals
form colorless white compounds
what sub shell are group 2 outer shell electrons in?
s
what type of reaction is the reaction between group 2 elements and oxygen
redox reaction
write an equation for the reaction of calcium and oxygen?
2Ca(s) + O2(g) –> 2CaO(s)
what type of reaction is the reaction between group 2 metals and water?
redox reaction
write an equation for the reaction of barium and water
Ba(s) + 2H2O(l) –> Ba(OH)2 (aq) + H2(g)
What is oxidised and what is reduced in a reaction between group 2 metals and water?
metal –> oxidised
one hydrogen from each water –> reduced
what are the products when group 2 oxides react with dilute acids?
salt and water
write the equation for the reaction of calcium and hydrochloric acid?
CaO(s) + 2HCl(aq) –> CaCl2(s) + H2O(l)
write the equation between calcium oxide and water
CaO(s) + H2O(l) –> M(OH)2 (aq)
which group 2 metal oxide is insoluble in water?
beryllium oxide
write an equation for the reaction between Mg(OH)2 and nitric acid
2HNO3 (aq) + Mg(OH)2 (aq) –> Mg(NO3)2 (aq) + 2H2O (l)
what is the trend of thermal stability in group 1 nitrates?
group 1 nitrates do not decompose except with the exception of lithium nitrate
the lithium ion is small enough to charge polarisation of the nitrate anion and therefore weakens the N-O bond
Explain the trend of electronegativity down group 7
Decreases going down the group
Atomic radii increases due to increasing number of shells
Reduced nuclear attraction between the outermost electron and nucleus
What is the trend in reducing ability of the halides going down the group?
Increases
I- is the strongest, because I- has the most occupied electron shells and so outer electrons are further from the nucleus
There is also weaker forces of attraction between the outer electrons and the + charge of the nucleus and therefore it is the easiest to be oxidised and lose electrons, therefore making it the best reducing agent
Which species is oxidised in this reaction?
Br2(l) + 2Na(s) –> 2NaBr(s)
Na
oxidation state of 0 to +1
Out of Cl-, Br- and I- which ones can be oxidised by chlorine
Br- and I-
Write the equation for chlorine oxidising bromide ions
Cl2(aq) + 2Br-(aq) –> 2Cl-(aq) + Br2(aq)
yellow solution
Write the equation for Cl2 oxidising 2I-
Cl2(aq) + 2I-(aq) –> 2Cl- (aq) + I2(aq)
purple solution
Out of Cl-, Br- and I- which can be oxidised by bromine?
I- ions
Write the equation for bromine oxidising iodide ions
Br2(aq) + 2I- (aq) –> 2Br-(aq) + I2(aq)
brown solution
Out of Cl-, Br- and I- which can be oxidised by iodine
none of them
Define disproportionation
The oxidation and reduction of the same element in a redox reaction
What type of reaction is the reaction of chlorine with water?
disproportionation
chlorine is both oxidised and reduced
What are the 2 forms of the chlorate ion?
ClO- chlorate (I)
ClO3- chlorate (V)
Show that the reaction of chlorine with hot dilute NaOH is a disproportionation reaction
3Cl2(aq) + 6NaOH(aq) –> 5NaCl(aq) + NaClO3(aq) + 3H2O(l)
Chlorine has been reduced and oxidised
Oxidation state: 0 to -1 in NaCl (reduction)
0 to +1 in NaClO3 (oxidation )
Why do you add HNO3 and not HCl when testing for halide ions?
To remove CO3 2-
Adding HCl would add Cl- ions and give a false positive result
What is the result and equation for Cl- test?
white precipitate
Ag+ + Cl- –> AgCl(s)
What is the result and equation for the test for Br-
cream precipitate formed
Ag+ + Br- –> AgBr(s)
What is the result and equation for the test for I-
yellow precipitate
Ag+ + I- –> AgI(s)
What happens to each of the silver halide precipitates when dilute/ concentrated NH3 are added?
AgCl- dissolves in both dilute and concentrated:
AgCl(s) + 2NH3(aq) –> [Ag(NH3)2]+ (aq) + Cl-
AgBr- only dissolves in concentrated
AgBr(s) + 2NH3(aq) –> [Ag(NH3)2]+(aq) + Br-
AgI- will not dissolve in either
What products are formed when I- reduces H2SO4?
[4 equations]
H2SO4 + 2I- –> SO4 2- + 2HI
H2SO4 + 2H+ + 2I- –> SO2 + I2 (SO2 is a choking gas with a pungent odour)
H2SO4 + 6H+ + 6I- –> S + 3I2 + 4H2O (S is a yellow solid
H2SO4 + 8H+ + 8- –> H2S + 4I2 + 4H2O (H2S smells of rotten eggs)
What are the products of Br- + H2SO4
HBr and SO2
Does Cl- reduce H2SO4
No
It is not a powerful enough reducing agents and only HCl is formed
What are anions known as?
negative ions
Write an equation for the carbonate ion test
CO3 2-(aq) + 2H+ (aq) –> H2O(aq) + CO2(g)
How can you test for sulfate ions?
Add dilute HCl and barium sulphate to the sample
If sulphates are present a white precipitate of barium sulfate is produced
Write an equation for the sulfate ion test
Ba2+ (aq) + SO4 2- (aq) –> BaSO4(s)
When testing for carbonate, sulfate and halide ions, in which order should the test be carried out and why?
Carbonate –> Sulfate –> Halide
Barium ions form insoluble precipitate of BaCO3 and silver ions form insoluble precipitate of Ag2SO4
What are cations known as?
Positive ions
How can you test for ammonium ions?
Add sodium hydroxide to the sample and warm it
Test the gas produced with red litmus paper
What are the observations for a positive ammonium ions test?
Red litmus paper turns blue
Ammonia has a pungent smell
Write the equation for ammonium ions test
NH4+(aq) + OH-(aq) –> NH3(aq) + H2O(aq)
