Chapter 8 Reactivity Trends Flashcards
What sub-shell are the outer electrons of group 2 elements in
S
What is the reaction of calcium becoming an ion
Ca → Ca2+ + 2e-
Why are group 2 elements called reducing agents
Group 2 element are called reducing agents because they have reduced another species. Group 2 elements are oxidised to produce 2+ ions
What do group 2 elements produce when they react with oxygen and what is the formula
Metal oxide
MO
What is the equation of Magnesium reacting with Oxygen
Mg(s) + ½O2(g) → MgO(s)
What are the half equations for the reaction and the Oxidation numbers:
Mg(s) + ½O2(g) → MgO(s)
Mg → Mg2+ + 2e-
0 → +2
Mg Oxidised
½O2 + 2e- → O2-
0 → -2 Reduced
What do group 2 metals react with water to produce and what is the formula
An alkaline hydroxide + Hydrogen Gas
M(OH)2
What are the observations of Group 2 elements reacting with water
- Bubbling
- Solid disappears
Does reactivity increase or decrease down group 2
Increases
What is the equation for the reaction of Strontium with Water
Sr(s) + 2H2O(l) → Sr(OH)2(aq) + H2(g)
In the reaction
Sr(s) + 2H2O(l) → Sr(OH)2(aq) + H2(g)
What has been oxidised and what has been reduced
Strontium Oxidised
Hydrogen Reduced
Group 2 Element + Dilute Acid →
Salt + Hydrogen
MASH
What is the equation for the reaction of Magnesium with Hydrochloric Acid
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
In the equation of Mg With HCl
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
What is oxidised and what is reduced
Mg Oxidised
H Reduced
How many ionisation energies does the formation of a 2+ ion involve
2
What is the equation of the first ionisation energy of a group 2 element M
M(g) → M+(g) + e-
What is the equation of the second ionisation energy of a group 2 element M
M+(g) → M2+(g) + e-
Why do the ionisation energies decrease down a group
- Atomic Radius Increases
- Inner Shell Shielding increases
- Nuclear Attraction decreases
Going down group 2, does the reducing ability increase or decrease
Increases
What is produced when group 2 Oxides react with water
hydroxide ions
alkaline solutions of the metal hydroxide
What is the equation of Calcium oxide with Water
CaO(s) + H2O(l) → Ca2+(aq) + 2OH-(aq)
How soluble are Group 2 Hydroxides in water
The Group 2 hydroxides are only slightly soluble in water
What happens when a solution of water and group 2 hydroxides becomes saturated
Any further metal and hydroxide ions will form a white precipitate
As you go down the group 2 hydroxides, do Solubility, Alkalinity and PH increase or decrease
Going down group 7
* solubility increases
* pH increases
* alkalinity increases
As solubility increases, the resulting solutions contain more OH-(aq) ions and are more alkaline
How is Calcium Hydroxide Ca(OH)2(a base) used in agriculture
is added to fields as lime by farmers to increase the pH of acidic soils in a neutralisation reaction
Ca(OH)2(s) + 2H+(aq) → Ca2+(aq) + 2H2O(l)
How are group 2 Bases used in medicine
Group 2 bases are often used as antacids for treating acid indigestion
Mg(OH)2(s) + 2HCl(aq) → MgCl2(aq) + 2H2O(l)
Magnesium and calcium carbonates are the main ingredients in indigestion tablets
Are group 7 elements oxidising agents or reducing agents
oxidising agents
What sub shells are the outer 7 electrons of group 7 elements in
2 are in the outer s sub-shell and 5 are in the outer p sub-shell
What colour is chlorine solution in water
Pale Green
What colour is Bromine solution in water I2(aq)
Orange
What colour is Iodine solution in water I2(aq)
Brown
What colour is Chlorine in a non-polar solvent
Pale Green
What colour is Bromine in a non-polar solvent
Orange
What colour is Iodine in a non-polar solvent
Purple
What state and colour is Fluorine in at RTP
Pale Yellow Gas
What state and colour is Chlorine at RTP
Pale Green Gas
What state and colour is Bromine at RTP
Red-Brown Liquid
What state and colour is Iodine at RTP
Shiny Grey - Black Solid
What state and colour is Astatine at RTP
Never been seen
Does the boiling point increase or decrease down the group 7
Increases
Why does the boiling point increase going down group 7
- More electrons
- Stronger London Forces
- More energy required to break the intermolecular forces
- Boiling Point increases
Does reactivity increase or decrease down group 7
Decreases down the group
Why does reactiity decrease down group 7
- Atomic Radius increases
- More inner shell shielding
- Less attraction to gain an element
- Reactivity decreases
Does oxidising ability increase or decrease down the group
Decreases
What is Disproportionation
A redox reaction in which the same element is both oxidised and reduced
What is the equation for the reaction of chlorine with water
Cl2(aq) + H2O(l) → HClO(aq) + HCl(aq)
What is the reaction of chlorine with cold dilute aqueous sodium hydroxide
Cl2(aq) + 2NaOH(aq) → NaClO(aq) + NaCl(aq) + H2O(l)
What is the benefit of chlorine use
Chlorine is beneficial in ensuring our water is safe to drink, by killing all bacteria present
What are the risks of Chlorine Use
Chlorine is an extremely TOXIC gas:
* in small concentrations it is a respiratory irritant.
* in large concentrations it can be fatal.
Chlorine added to drinking water can react with organic hydrocarbons, such as methane, to form chlorinated hydrocarbons – a suspected carcinogen
Cl2(aq) + 2Br-(aq) →
2Cl-(aq) + Br2(aq)
Cl2(aq) + 2I-(aq) →
2Cl-(aq) + I2(aq)
Br2(aq) + 2I-(aq) →
2Br-(aq) + I2(aq)
How do you test for halide ions
Add aqueous silver ions to aqueous halide ions to form a precipitate of silver halide
What is the ionic equation for testing for Halide ions
Ag+(aq) + X-(aq) → AgX(s)
What colour is the precipitate formed when testing for Chloride ions
Is it soluble in Dilute NH3 or Concentrated NH3 or not at all
White
Soluble in dilute NH3
What colour is the precipitate formed when testing for Bromide ions
Is it soluble in Dilute NH3 or Concentrated NH3 or not at all
Cream Precipitate
Soluble in concentrated NH3
What colour is the precipitate formed when testing for Iodide ions
Is it soluble in Dilute NH3 or Concentrated NH3 or not at all
Yellow Precipitate
Insoluble in concentrated NH3
How do you test for Carbonates
Add dilute nitric acid to a test tube containing the unknown compound
Observation - Bubbles of gas
What is the ionic equation for a Carbonate test
CO32-(aq) + 2H+ → CO2(g) + H2O(l)
How do you test for sulfates
Add barium nitrate to a test tube containing a solution of the unknown compound
Observation – a white precipitate (of barium sulfate) forms
What is the ionic equation for the sulfate test
Ba2+(aq) + SO42-(aq) → BaSO4(s)
What is the order you should perform the anions tests in
- Carbonate, CO32-
- Sulfate, SO42-
- Halides, Cl-, Br-, I-
Why do you do the anion tests in this order:
1. Carbonate, CO32-
2. Sulfate, SO42-
3. Halides, Cl-, Br-, I-
- If carbonate ions are present when testing for sulfate ions (addition of barium nitrate) – a white precipitate of barium carbonate, BaCO3(s), will form.
- If carbonate ions and/or sulfate ions are present when testing for halide ions (addition of silver nitrate) – white precipitates of silver carbonate, Ag2CO3(s), and/or silver sulfate, Ag2SO4(s) will form.
