Topic 4 Inorganic Chemistry Flashcards
What is a common name given to group 2 metals?
Alkaline earth metals
What is the most reactive metal of group 2?
Barium
List 3 physical properties of group 2 metals
● High melting and boiling points
● Low density metals
● Form colourless (white) compounds
The highest energy electrons of group 2 metals are in which subshell?
S subshell
Does reactivity increase or decrease down group 2? Why?
● Increases
● Electrons are lost more easily because larger
atomic radius and more shielding.
What happens to the first ionisation energy as you go down group 2? Why?
Decreases because:
-Number of filled electron shells increases down the group →
increased shielding
- Increased atomic radius → weaker force between outer - - -Electron and nucleus → less energy needed to remove electron
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) + O 2 (g) → 2CaO (s)
What is the product when group 2 elements react with water?
Hydroxide and hydrogen gas
Which group 2 element doesn’t react with water?
Beryllium
Which group 2 element reacts very slowly with water?
Magnesium
What type of reaction is the reaction between group 2 metal and
water?
Redox reaction
Write an equation for the reaction of Barium and water
Ba (s) + 2H 2 O (l) → Ba(OH)₂ (aq) + H₂ (g)
What is oxidised and what is reduced in a reaction between group
2 metal and water?
Metal → oxidised
One hydrogen atom from each water → reduced
What are the products when group 2 oxide reacts with dilute acid?
Salt and water
Write an equation for the reaction of calcium and hydrochloric acid
CaO (s) + 2HCl (aq) → CaCl 2 (s) + H₂O (l)
What is formed when group 2 oxides react with water?
Metal hydroxide
Write an equation for the reaction between a group 2 oxide and
water
MO (s) + H 2 O (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
2HNO 3 (aq) + Mg(OH) 2 (aq) –> Mg(NO 3 ) 2 (aq) + 2H2O (l)
What is the trend in hydroxide solubility down group 2?
Increases down the group
Ca(OH)₂ is slightly soluble
Ba(OH)₂ creates a strong alkaline solution
What is the trend in sulphate solubility down group 2?
Group 2 sulphates become less soluble down the group with BaSO4 being the least soluble
Explain the reasons 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 Lithium ion is small enough to have a polarising effect so therefore lithium carbonate can decompose.
Explain the reasons for the trend of thermal stability in group 2 carbonates
Group 2 carbonates are more thermally stable as you go down the group this is because the cations get bigger so therefore have less of a polarising effect distorting the carbonate ion less. As C-O bond is not weakened as much it harder to break down
Explain the reasons for the trend of thermal stability in group 1 nitrates
Group 1 nitrate do not decompose with the exception of Lithium nitrate. Lithium ion is smaller enough to charge polarisation of the nitrate anion and thus weakening
the N-O bond.
Explain the reasons for the trend of thermal stability in 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 has less charge density = less polarisation of nitrate anion and less weakening of the N―O bond
What is the flame colour of Lithium
Red
What is the flame colour of Sodium
Yellow
What is the flame colour of Potassium
Lilac
What is the flame colour of Magnesium
none, cuz the photons emitted has a frequency outside the visible light spectrum
What is the flame colour of Calcium
Brick red
What is the flame colour of Strontium
Red
What is the flame colour of Barium
Apple green
How do you carry out a flame test?
- Use a nichrome wire
- Sterilise the wire by dipping in concentrated hydrochloric acid and then heating in Bunsen flame
- Make sure the sample powdered or grinded
- Dip wire in solid and put in Bunsen flame and observe flame
How are the colours from the flame test formed?
The heat causes the electron to get excited and thus move to a higher energy level but at this higher level the electron is unstable so then moves back down. As it moves from a higher to lower energy level energy is emitted in the form of visible light energy which is the colour you see.
List 2 properties of halogens
● Low melting and boiling points
● Exist as diatomic molecules
What is the trend in boiling point down group 7? Why?
Increases down the group because:
-size of atom increases as more occupied electron shells
→ stronger London forces of attraction between molecules, take
more energy to break
What is the trend in reactivity down group 7? Why?
Reactivity decreases because:
● Atomic radius increases
● Electron shielding increases
● Ability to gain an electron and form 1- ions decreases
Explain the trend of electronegativity down group 7
Down the group the electronegativity of the elements decreases. This is because the atomic radii increases due to the increasing number of shells so there is reduced nuclear attraction between the outermost electron and the nucleus.
What is the trend in oxidising ability down the group? Why?
Decreases down group (Cl strongest, I weakest)
This is because Cl has the fewest occupied electron shells, greatest force of attraction between outer electrons and nucleus and thus is the easiest to gain electrons and be reduced → best oxidising agent
Which species is oxidised in this reaction: Br 2 (l) + 2Na (s) 2NaBr (s)
Na has been oxidised
Oxidation state of 0 to +1
When a more reactive halogen displaces a less reactive halide, what is the reaction called?
Displacement reaction
What is the colour of chlorine in water?
Pale green
What is the colour of bromine in water?
Yellow/Orange
What is the colour of iodine in water?
Brown
What is the colour of chlorine in cyclohexane?
Pale green
What is the colour of bromine in cyclohexane?
Red
What is the colour of iodine in cyclohexane?
Purple
Out of the 3 halides Cl -, Br - & I - , which one of these can be oxidised by chlorine?
Br - & I - ions
Write the equation for chlorine oxidising bromide ions in water and associated colour change
Cl₂ (aq) + 2Br- (aq) → 2Cl- (aq) + Br₂ (aq)
Yellow solution
Write the equation for Cl 2 oxidising 2I-
Cl₂ (aq) + 2I- (aq) → 2Cl- (aq) + I₂ (aq)
Purple solution
Out of the 3 halides Cl- , Br- & I- , which one of these can be oxidised by bromine?
I - ions
Write the equation for bromine oxidising iodide ions in water and associated colour change
Br₂ (aq) + 2I- (aq) → 2Br- (aq) + I₂ (aq)
Brown solution
Define disproportionation
The oxidation and reduction of the same element in a redox reaction
What is the equation for the reaction of Cl 2 with water?
Cl₂ (g) + H₂O (l) → HClO (aq) + HCl (aq)
What type of reaction is the reaction of chlorine with water?
Disproportionation; chlorine is both oxidised and reduced
Why is chlorine added to drinking water?
It kills the bacteria in the water and makes it safer to drink
What are the two forms of the chlorate ion?
ClO- is chlorate (I)
ClO₃- is chlorate (V)
What is the equation for forming bleach + conditions?
Cold dilute alkali
Cl₂ (aq) + 2NaOH (aq) → NaCl (aq) + NaClO (aq) + H₂O (l)
NaClO is bleach
Show that the reaction of chlorine with hot dilute NaOH is a disproportionation reaction
3Cl 2 (aq) + 6 NaOH(aq) → 5 NaCl (aq) + NaClO 3 (aq) + 3H 2O (l)
Chlorine is been reduced and oxidised.
Oxidation state of chlorine has gone from:
0 to -1 in NaCl = reduction
0 to +1 in NaClO 3 = oxidation
What do you use to test for halide ions?
Acidified AgNO 3
Why do you add HNO 3 in a halide test? Why not HCl?
To remove CO₃2-
Adding HCl would add Cl- ions, giving a false positive result
Result and ionic equation for Cl - test?
white ppt
Ag + + Cl - → AgCl (s)
What is the result and ionic equation for the test for Br -?
Cream ppt
Ag + + Br - → AgBr (s)
What is the result and equation for the test for I -?
Yellow ppt
Ag + + I - → AgI (s)
What happens (+ equations) to each of the silver halide precipitates when dilute/conc NH 3 are added?
AgCl dissolves in both dilute and conc
AgCl (s) + 2NH₃ (aq) → [Ag(NH₃)₂]+ (aq) + Cl -
AgBr only dissolves in conc
AgBr (s) + 2NH₃ (aq) → [Ag(NH₃)₂]+ (aq) + Br -
AgI will not dissolve in either
What is the trend in oxidising ability down group 7? Why?
Decreases down group (Cl best, I worst)
Because: Cl has fewest occupied electron shells, greatest force of attraction between outer electrons and nucleus, easiest to gain electrons and be reduced → best oxidising agent
What is the trend in reducing ability of the halides
down the group? Why?
Increases down the group (Cl - worst, I - best)
Because: I - has the most occupied electron shells, so outer electrons are further from the nucleus, weakest force of attraction between outer electrons and positive charge of nucleus → easiest to be oxidised and lose electrons → best reducing agent
What products are formed when l - reduces H 2SO 4?
Do equations for all 4.
H₂SO₄ + 2l - → SO₄2- + 2Hl
H₂SO₄ + 2H + + 2l - → SO₂ + l₂ + 2H₂O (SO 2 is a choking gas with a pungent odour)
H₂SO₄ + 6H + + 6l - → S + 3l₂ + 4H₂O (S is a yellow solid)
H₂SO₄ + 8H + + 8l - → H₂S + 4I₂ + 4H₂O (H2 S smells of bad/rotten eggs)
What are the products of Br - + H 2SO 4?
HBr and SO₂
Does Cl - reduce H 2SO 4?
No, not a powerful enough reducing agent; only HCl is formed
What are anions also known as?
Negative ions
How can you test for carbonate ions, CO3 2-?
Add strong acid to the sample
Collect the gas produced
Pass through lime water
What are the observations for a positive test of carbonate ions,
CO3 2-?
Fizzing
Limewater turns cloudy
Write an equation for the carbonate ion test
CO3 2- (aq) + 2H + (aq) → H 2 O (aq) + CO 2
(g)
How can you test for sulphate ions, SO 42- ?
Add dilute hydrochloric acid and barium chloride to the sample
What are the observations for a positive test of sulfate ions, SO 4 2- ?
White precipitate of barium sulfate is produced
Write an equation for the sulfate ion test
Ba 2+ (aq) + SO 4 2- (aq) → BaSO 4 (s)
When testing for carbonate, sulfate and halide ions, in which order should the tests be carried out and why?
- Carbonate test
- Sulfate test
- Halide test
Because barium ions forms insoluble precipitate of BaCO 3 and silver ions form insolube precipitate of Ag2 SO 4
What are cations also known as?
Positive ions
How can you test forammonium ions, NH4 + ?
Add sodium hydroxide to the sample and warm it
Test the gas produced with red litmus paper
What are the observations for 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) → NH 3 (aq) + H 2 O (aq)
