ES Flashcards
Equation for atom economy
(Mr of desired products / Mr of reactants) x 100
Which blocks are these?
What is the charge of a group 7 element?
1-
What is disproportionation?
When a species is simultaneously reduced and oxidized to give two different products
What does oxidation mean?
.Gain of oxygen
.Loss of electrons
.An increase in oxidation number
What does reduction mean?
Loss of oxygen
Gain of electrons
Decrease in oxidation number
Half equation for reduction
Cl2 + 2e- —> 2Cl-
Half equation for oxidation
2Br- -> Br2 + 2e-
What is the oxidation state for an atom in an element? Eg. O2, Mg, Cl2
0
How do you work out the oxidation states of the elements in a compound?
Oxidation states of all the elements must add up to 0 if the compound has no overall charge
- Some elements have oxidation states which never change
Oxidation state of flourine
-1
Oxidation state of oxygen in a compound
-2 (except when combined with F)
Oxidation state of chlorine in a compound
-1 (except when combined with O or F)
Oxidation state of bromine in a compound
-1 (except when combined with Cl, O or F)
Which element will retain its oxidation state in a compound?
The more reactive element
What is the oxidation state of iodine in a compound?
-1 (except when reacted with F, O, Cl, Br)
What is the oxidation state of hydrogen in a compound?
+1 (except in a metal hydride eg, NaH)
What is the oxidation state of a group one element in a compound?
+1
What is the oxidation state of a group 2 element in a compound?
+2
What is the oxidation state of a group 3 element in a compound?
+3
What do the oxidation states add up to in PO4 3-?
-3
How to work out systematic names
1) identify the name of the compound
2) work out the variable the element which has a variable oxidation state
3) work out its oxidation state
4) place the oxidation number in Roman numerals next to the variable element
Oxidation state on 2I-
Still -1
What does a decrease in oxidation state mean?
REDUCED
How to name an oxyanion
Place the oxidation number in Roman numerals in brackets after the -ate
What is electrolysis?
The decomposition of a molten or aqueous ionic compound by passing an electric current through it
What are the 2 electrodes?
Cathode - negative
Anode - positive
What happens to cations and anions during electrolysis?
Cations (positive ions) are reduced at the cathode
Anions (negative ions) are oxidised at the anode
When will hydrogen gas pass at the cathode?
If the solution is acidic
OR
If a group 1 or 2 or aluminium metal is at the cathpde
Equation at the cathode if the solution is acidic
2H+ (aq) + 2e- -> H2 (g)
Equation at the cathode if the solution contains a group 1, 2 or aluminium metal
2H2O(l) + 2e- -> 2OH-(aq) + H2(g)
What happens if a less reactive metal (not group 1 or 2) is at the cathode?
Metal atoms are formed
Metal ion (aq) + electrons -> metal atom (s)
What happens to when the anode and metal solution are the same?
Metal anode loses mass as metal atoms change to ions and go into the solution
What happens to sulfates and nitrates at the anode?
Oxidized less easily than water so oxygen gas is produced at the anode
2H2O -> O2 + 4H+ + 4e-
What happens to halide ions at the anode?
HAlogen is produced at the anode as they are oxidized more easily than water
2Cl- -> Cl2 + 2e-
what are the colours and states of the halogens room temp and pressure?
Flourine - Pale yellow gas
Chlorine - Pale green gas
Bromine - red/brown liquid
Iodine - dark grey solid
What happens to volatility down the group of halogens?
Increases
What colours are chlorine, bromine and iodine in aqueous state?
Chlorine - green
Bromine - Orange
Iodine - Brown
Why are halogens more soluble in organic solvents than water?
Because halogens are non-polar molecules so they’re more soluble in non-polar solvents
Why does reactivity decreases down group 7?
Atomic radius increases
Shielding increases
Positive attraction of the nucleus is weakened
Harder to gain an electron for bonding
What happens to oxidising power down the group?
Decreases
Ability to attract electrons decreases
As greater atomic radius
So more shielding
when will a halogen displace a halide from a solution?
If the halide ion is below it on the periodic table
Chlorine + bromide color change
Colorless -> orange
chlorine + iodide color change
Colorless -> brown
Bromine + iodide color change
Orange -> brown
What is formed when chloride, bromid and iodide ions react with silver nitrate?
Cl- = white precipitate (AgCl)
Br- = cream precipitate
I- = yellow precipitate
What happens when chlorine, bromide and iodide ions react with ammonia?
I- nothing
Br- dissolves in concentrated ammonia
Cl- dissolves in dilute ammonia
Halide ion + concentrated sulfuric acid ->
Hydrogen halide + sulfate salt
What happens to thermal stability down group 7?
HF and HCl are very thermally stable so will not split when heated
HBr will split when heated
HI will split more easily
Why does thermal stability decrease down group 7?
Covalent bonds are weaker
As halogen atoms are larger
So bonding pair is further from nucleus
So they can be broken more easily
Where do dynamic equilibriums occur?
In closed systems
What happens to equilibrium if you increase temp?
Will shift to favor the endothermic reaction as heat needs to be lost
What happens to equilibrium if you decrease temp?
Will shift to favor the exothermic reaction as heat needs to be gained
What happens to equilibrium if you increase pressure?
Shift to the side with fewer molecules
What happens to equilibrium if you decrease pressure?
Will shift to the side with more molecules
What happens to equilibrium if you increase concentration?
Forward reaction will be favored
Increases yield of products on the right hand side
What happens to equilibrium if you decrease concentration?
Reverse reaction will be favored
Increases yield of reactants on the left hand side
Equation for equilibrium constant
