UNIT 2 Section 2 - Group 2 and Group 7 elements Flashcards
What is the trend in reactivity in group 2 and why
reactivity increases down the group as ionisation energies decrease due to increasing shielding and atomic radius increases so easier to lose electrons
The test for reactivity of group 2 metals and results
add to dilute hydrochloric acid and observe vigorous reactions and effervesance and the metals further down the group will be more reactive
What is the trend of the melting point down group 2
melting point decreases down the group as the atomic radius increases an the electrostatic forces of attraction are weaker
What is the trend in density of group 2 metals down the group
the density increases down the group as the atomic radius is so big
What is the trend in solubility of group 2 hydroxides down the group
the solubility of group 2 hydroxides increases down the group
If the solubility in a group 2 metal is high what does that mean in terms of OH ions
more will be present in the soltuion and therfeore the solution will be more alkaline
what is the equation of group 2 hydroxide ions dissolving
X(OH)2 —-> X+2 + 2OH-
What is the trend in the solubility of group 2 sulfates
the solubility of group 2 sulfates decreased down the group
what is the general equation of group 2 metals reacting with oxygen
2M +O2 —> 2MO
What group 2 metals also form peroxides when reacting with oxygen
barium and strontium from BaO2 and SrO2
what is the general equation for metals reacting with water
M + 2H2O –> M(OH)2 +H2
what group 2 metal doesnt react with water
beryllium
what group 2 metal reacts slowly with water and what other way can it react with water and what does it produce
magnesium reacts extremely slowly with liquid water but it can react vigourously with stream to make magnesium oxide and gas
what do group 2 metals make result wise when reacted with dilute HCL
colourless solutions of metal salts and hydrogen gas
what is the general equation when a group 2 metal racts with dilute HCL
M + 2HCL –> MCl2 + H2
what do group 2 metals form when they react with sulfuric acid 2 types of
insoluble sulphate is formed with strontium and barium and the rest of group 2 is a soluble sulphate
what is the general equation for the reaction of metals with dilute H2SO4
M + H2SO4 –> MSO4 + H2
what happens when you react barium and strontium with sulfuric acid in terms of the solid oxide
they form an insoluble sulphate at the surface which stops the solid oxide beneath reacting with the acid
what 3 products do group 2 carbonates form when reacted with hydrochloric acid
they form a soluble chloride salt, water and carbon dioxide
what group 2 carbonates form insoluble sulphate layers and what does it cause
calcium, barium and strontium from an insoluble sulphate layer on their solid carbonates which means the solid carbonate cant react with the acid and the reaction stops
what is seen when you add a carbonate to a dilute acid
bubbling of CO2 is produced
what is the use of calcium hydroxide
neutralise the pH of fields
what can calcium carbonate be used for
neutralising fields and removing sulfur dioxide from flue gases
what is barium sulphate used for
it is used as a barium meal for pateints getting xrays on their intestines as it highlights them by absorbing the xrays
why is barium sulphate safe to use in xrays
it is insoluble and won’t get absorbed into blood
what is the use of magnesium hydroxide and how does it work
it is used to treat indigestion as it is slightly soluble so will from a slight alklaine solution which neutralises the HCL in the stomach
what is the use of magnesium and what are the equations
magnesium is used in the extraction of titanium from its ore
TiO2 + 2Cl + C –> TiCl4 + CO2
TiCL4 + Mg –> Ti + 2MgCl2
what is the trend in group 7 boiling points down the group
boiling point increases as the van der waals in diatomic molecules get stronger as the elements get bigger due to increasing atomic radius
what is the trend in group 7 volatility going down the group and why
the volatility decreases as boiling points increase due to van der waals getting stronger
what is the trend in oxidising power going down group 7 and why
it decreases as they become less electronegative due to an increase in atomic radius meaning the joining electron will experience more shielding and less attraction to the nucleus
what is the trend in reducing power of halides down the group
the reducing power increase down the group due to how easiliy electrons are lost because of shielding ang a large atomic radius resulting is less attraction between nucleus and electronsso they are held less tightly
what is the test for halide ions
- dissolving the solution in nitric acid to remove carbonate ions
- add silver nitrate drop by drop and a precipitate will form
- then add dilute ammonia to dissolve chlroide
- then add concentrated ammonia to dissolve bromide
what are the results for positive halide ion test
chloride- white
bromide- cream
iodide- yellow
what are the equations for the reaction between concentrated sulfuric acid and fluorine
H2SO4 + NaF –> NaHSO4 + HF
what are the equations for the reaction between concentrated sulfuric acid and chlorine and what are the state symbols
H2SO4 + NaCl –> NaHSO4 + HCl
H2SO4 is liquid
NaCl is solid
NaHSO4 is a solid
HCl is a white gas
what are the equations for the reaction between concentrated sulfuric acid and bromine
H2SO4(l)+ NaBr(s) –> NaHSO4(s)+ HBr(g)
H2SO4(l) + HBr(g) –> Br2(g) + SO2(g) + H2O(l)
what are the equations for the reaction between concentrated sulfuric acid and iodine
H2SO4 (l)+ NaI(s) –> NaHSO4(s) + HI (g)
H2SO4 (l)+ 2HI(g) –> I2(g) + SO2(g) + 2H2O(l)
H2SO4(l) + 6HI(g) –> 3I2(g)+ S(s) + 4H2O(l)
H2SO4(l) + 8HI(g) –> 4I2(g) + H2S(g) + 4H2O(l)
what are the results/observations of the reaction between concentrated sulfuric acid and chloride
white fumes of HCl gas
what are the results of the reaction between concentrated sulfuric acid and bromide
white misty fumes of HBr and reddish brown gas of Br2
what are the results of the reaction between concentrated sulfuric acid and iodine
violet/ purple vapour of I2
yellow solid of sulfur
strong bad smell of H2S
what is a dispropotionation reaction
a reaction where the same species is oxidised and reduced
how is bleach made
2NaOH(aq) + Cl2 (g) –> NaCl (aq) + NaClO (aq)+ H2O (l)
what is the use of chlorine
chlorine is used to clean water and make it drinkable and to keep swimming pools clean
what compound is made in the reaction of chlorine and sodium hydroxide that cleans that water
NaClO
NaCLO is bleach
ClO- is chlorate (i)
even though there are toxic effects of using chlorine to kill bacteria why do we do it
the benefits of clean water by chlorine killing bacteria outweighs its risk of toxic effects
why is keeping shallow pools more difficult/expensive
shallow pools lose chlorine rapidly from the water due to evaporation so it costs more
put chlorine, iodine and bromine in order of reactiveness and what ones would displace what
chlorine
bromine
iodine
what solutions forms when iodine is displaced by bromine
a brown solution of iodine (I2)
what colour solution forms when bromine is displaced by chlorine and what are the products of the reaction
a orange solution of bromine (Br2)
KCl + Br2
what can you do to test for compounds of some group 2 metals using a bunsen
flame spec
1. dip a nichrome wire loop in concentrated hydrochloric acid to clean it
2. then dip it into compound
3. hold the loop in the clear blue part of a bunsen burner flame
results for group 2 metal ions in flame spec
calcium- brick red
strontium- red
barium- pale green
how can you use dilute sodium hydroxide to identify group 2 ions and what are the results
- add dilute sodium hydroxide solution in excess
- dropwise to a test tube containing the metal ion and observe precipitate
magnesium white precipitate when NaOH is in excess ( before excess is slightly white)
calcium slightly white precipitate
strontium slightly white precipitate
barium is no change
what are the test tube results of adding sodium hydroxide to group 2 ions Mg, Ca, Sr, Ba
Mg- white precipitate
Ca- slight white precipitate
Sr- slight white precipitate
Ba- no change
what is the test for ammonium ions and what is the equation for the reaction
- add dilute sodium hydroxide
- gently heat the mixture
- then add damp red litmus paper and it should go blue
NH4+ + OH- —->NH3 + H2O
what is the test for sulfate ions and whats a positive result
- add dilute hydrochloric acid to remove carbonates as they can give false results
- add barium chloride solution
- a white precipitate is a positive test as barium sulphate is formed
what is the test for hydroxide ions
dip a damp piece of red litmus paper into the solution and hydroxide ions turn the litmus paper blue
test for carbonate ions
- add dilute hydrochloric acid
- carbon dioxide is released
- CO2 turns limewater cloudy so bubble the gas through the test tube of limewater to get a result
why is using chlorine in outdoor pools risky for the environment
it is risky because they can produce chlorinated hydrocarbons
what is the equation when chlorine reacts with water
Cl2(g) + H2O (l) <–> ClO- (aq) + 2H+ (aq) + Cl- (aq)
what can chlorine do in the presence of sunlight and what is the equation
decompose
Cl2 (g)+ H20 (l) <–> 2Cl- (aq) + 2H+ (aq) + 1/2 O2(g)
if you react NaF with with silver nitrate what do you get
a colourless solution
what are the equations for the removal of sulfur dioxide from flue gases
CaO(s) + SO2(g) –> CaSO3(s)
CaCO3(s) + SO2 (g) –> CaSO3 (s) + CO2(g)
what is the trend in electronegativity down group 7
electronegativity decreases down the group as larger atoms attract eletrons less due to the outer electrons being further from the nucleus and more shielded as they have more inner electrons so the tendency to attract an atom lowers
what happens to the first ionisation energy as you go down group 2 and why
decreases and the number of shielding electrons increases and an increase in atomic radius which means weaker forces between valence electrons and nucleus so less energy needed to remove electron
write and equation for the reaction of magnesium and steam
Mg(s) + H2O(g) —> MgO(s) + H2 (g)
what are flue gases
gases produced by power stations which are harmful to the environment
what is Ca(OH)2 used for and write an equation related to one of its uses
used to neutralise the soil
Ca(OH)2 + 2HCL —> 2H2O + CaCl2
what is the trend in electronegativity down group 7
decreases as there are more shells so more shielding and a greater atomic radius so a lower force of attraction between the nucleus and electron pair in a covalent bond
what state and colour is fluorine at room temp
pale yellow gas
what state and colour is chlorine at room temp
green gas
what is the state and colour of bromine at room temp
brown orange liquid
what is the state and colour of iodine at room temp
grey solid
what is the rule for displacement reactions in group 7
a halogen will displace a halide from solution if the halide is lower is the periodic table
