groups p1 Flashcards
what is a common name given to group 2 metals?
alkaline earth metals
what is the most reactive metal of group2?
Barium
list 3 physical properties of group 2 metals
high melting and boiling points
low density metals
from 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
number of filled electron shells increases down the group –> increased shielding
increased atomic radius –> weaker force between outer electrons
electron and nucleus –> less energy needed to remove electron
what type of reaction is the reaction between group 2 elements and oxygen?
redox
equation for the reaction of calcium and oxygen
2Ca(s) + O2(g) –> 2CaO(s)
what are the products 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
equation of barium and water
Ba(s) + 2H2O(l) –> Ba(OH)2(aq) + H2(g)
what is oxidised adn 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 a group 2 oxide reacts with a dilute acid?
salt and water
equation of calcium oxide and hydrochloric acid
CaO(s) + 2HCl(aq) –> CaCl2(s) + H2O(l)
what is formed when group 2 oxides react with water?
metal hydroxide
equation for the reaction between a group 2 oxide and water?
MO(s) + H2O(l) –> M(OH)2(aq)
what group 2 metal oxide is insoluble in water?
beryllium oxide
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 in hydroxide solubility down group 2?
increases
Mg(OH)2 is slightly soluble
Ba(OH)2 creates a strong alkaline solution
what is the trend in sulphate solubility down group 2?
decreases
BaSO4 - least soluble
what is the trend of thermal stability in g 1 carbonates?
g 1 carbonates do not decompose except for lithium - they don’t have a big enough charge density to polarise the carbonate ion (only form 1+ ions) - Li ion is small enough to have a polarising effect so therefore lithium carbonate can decompose
what is the trend of thermal stability in g 2 carbonates?
increases down the group because the cations get bigger so have less polarising effect distorting the carbonate ion less - C-O bond is not weakened as much - harder to break down
what is the trend of thermal stability in g 1 nitrates?
do not decompose expect lithium nitrate - lithium ion small enough to charge polarisation of the nitrate anion and thus weakening the N-O bond
what is the trend of thermal stability in g 2 nitrates?
increases - ions get larger and therefore have less charge density = less polarisation of nitrate anion and less weakening of the N-O bond
flame tests: Li
scarlet red
flame tests: Na
yellow
flame tests: K
lilac
flame tests: Rb
red
flame tests: Cs
blue
flame tests: Mg
no flame colour
flame tests: Ca
brick red
flame tests: Sr
red
flame tests: Ba
apple green
how do you carry out a flame test?
1 use a nichrome wire
2 sterilise by dipping in conc HCl and heating in bunsen flame
3 dip wire in (powdered) solid and put in flame
4 observe colour
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 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
which group are referred to as halogens?
group 7
properties of the halogens?
low melting and boiling points, exist as diatomic molecules
trend in boiling point down group 7?
increases
size of atom increases as more electron shells –> stronger London forces between molecules requiring more energy to break
trend in reactivity down group 7?
decreases
atomic radius increases, electron shielding increases, ability to gain an electron and form 1- ions decreases
trend in electronegativity down g 7?
decreases
atomic radii increases so there is reduced nuclear attraction between outermost electron and the nucleus
trend in oxidising ability down g 7?
decreases (Cl strongest, I weakest)
Cl has 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
trend in reducing ability of group 7?
increases (Cl- weakest, I- strongest)
I- has greatest atomic radius, weakest force of attraction between outer electrons and positive charge of nucleus and thus is the easiest to be oxidised and lose electrons –> best reducing agent
what colour is chlorine in water? in cyclohexane?
pale green
pale green
what colour is bromine in water? in cyclohexane?
orange
orange
what colour is iodine in water? in cyclohexane?
brown
violet
out of Cl-, Br-, I- which can be oxidised by chlorine?
Br- and I-
equation of chlorine oxidising bromide ions in water and colour change
Cl2(aq) + 2Br-(aq) –> 2Cl-(aq) + Br2(aq)
yellow solution
equation of chlorine oxidising iodide ions in cyclohexane and colour change
Cl2(aq) + 2I-(aq) –> 2Cl-(aq) + I2(aq)
purple solution
out of Cl-, Br-, I- which can be oxidised by bromine?
I- ions
equation for bromine oxidising iodide ions in water and colour change
Br2(aq) + 2I-(aq) –> 2Br-(aq) + I2(aq)
brown solution
out of Cl-, Br-, I- which can be oxidised by iodine?
does not oxidise Cl- or Br-
disproportionation
the oxidation and reduction of the same element in a redox reaction
what is the equation of Cl2 with water?
Cl2(g) + H2O(l) –> HClO(aq) + HCl(aq)
disproportionation reaction
why is chlorine added to drinking water?
kills the bacteria in the water and makes it safer to drink
what are the two forms of the chlorate ion?
ClO^- chlorate (I)
ClO3^- chlorate (V)
equation for forming bleach? conditions?
(NaClO is bleach)
Cl2(aq) + 2NaOH(aq) –> NaCl(aq) + NaClO(aq) + H2O(l)
cold dilute alkali
equation of chlorine and hot dilute NaOH
3Cl2(aq) + 6NaOH(aq) –> 5NaCl(aq) + NaClO3(aq) + 3H2O
disproportionation
how do you test for halide ions? results?
acidified AgNO3
Cl- = white ppt
Br- = cream ppt
I- = yellow ppt
when testing for halide ions why do you add HNO3 not HCl?
to remove CO3 2-
adding HCl would add Cl- ions, giving a false positive result
what happens to each of the silver halide precipitates when dilute/conc NH3 is added?
AgCl- dissolves in both dilute and conc
AgBr- dissolves in conc
AgI- does not dissolve
trend in oxidising ability down g 7?
decreases down group (Cl best, I worst)
Cl has fewest occupied electron shells therefore greatest attraction between outer electrons and nucleus, easiest to gain electrons and be reduced
trend in reducing ability down group 7?
increases down group (Cl- worst, I- best)
I- has 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
what products are formed when I- reduces H2SO4?
H2SO4 + 2I- –> SO4 2- + 2HI
H2SO4 + 2H+ + 2I- –> SO2 + I2 + 2H2O (SO2 is a choking gas with a pungent odour)
H2SO4 + 6H+ + 6I- –> S + 3I2 + 4H2O (S is a yellow solid)
H2SO4 + 8H+ + 8I- –> H2S + 4I2 + 4H2O (H2S smells of rotten eggs)
products of Br- and H2SO4?
HBr and SO2
does Cl- reduce H2SO4?
no - only HCl is formed
how can you test for carbonate ions (CO3 2-)?
add strong acid
collect the gas produced
pass through lime water
limewater turns cloudy and effervescence is positive
CO3 2-(aq) + 2H+ (aq) –> H2O(aq) + CO2(g)
how can you test for sulfate ions (SO4 2-)?
add dilute HCl and barium chloride/nitrate
white ppt of barium sulfate is produced
Ba 2+(aq) + SO4 2-(aq) –> BaSO4(s)
what do you use to test for halide ions?
acidified AgNO3
when testing for carbonate, sulfate and halide ions, in which order should the tests be carried out and why?
1 carbonate
2 sulfate
3 halide
barium ions form insoluble ppt of BaCO3 and silver ions form insoluble ppt of Ag2SO4
how can you test for ammonium ions (NH4 +)?
add NaOH to the sample and warm it
test the gas produced with red litmus paper
red litmus paper turns blue, pungent smell
NH4 +(aq) + OH-(aq) –> NH3(aq) + H2O(aq)
