Group 2 / Group 7 Flashcards
By what name are the group II metals also known?
alkali earth metals
State and explain the trend in atomic radius down group 2
Size increases down the group
Shielding increases
So the outer shell electrons are further from the nucleus
State and explain the trend in first ionization energy down group 2
On descending the group
Shielding increases
Attraction between the nucleus and outer electrons decreases
State and explain the trend in melting point down group 2
The size of the cations increases down the group
Attraction between cations and delocalised electrons decreases
So the metallic bonding gets weaker
State and explain how the reactivity of the group II elements to water changes down the group
On descending the group
Shielding increases
Attraction between nucleus and outer electrons decreases
Outer electrons are more easily lost
write an equation for the reaction of magnesium with steam
Mg(s) + H2O(g) –> MgO(s) + H2(g)
write an equation for the reaction of calcium with water
Ca(s) + 2H2O(l) –> Ca(OH)2(s) + H2(g)
write an equation for the reaction of barium with water
Ba(s) + 2H2O(l) –> Ba(OH)2(s) + H2(g)
State two differences you would observe in the reactions of calcium and barium with water
the reaction with calcium would be slower and the solution would go cloudy
State the trend in the solubility of the Group II sulphates
decreases down group
State the trend in the solubility of the Group II hyrdoxides
increases down group
State what you would observe when barium chloride and sulphuric acid are mixed, and write ionic equations for any reactions you observe
white precipitate
Ba2+(aq) + SO42-(aq) –> BaSO4(s)
State what you would observe when barium chloride and sodium hydroxide are mixed, and write ionic equations for any reactions you observe
no reaction
State what you would observe when magnesium chloride and sodium hydroxide are mixed, and write ionic equations for any reactions you observe
white precipitate: Mg2+(aq) + 2OH-(aq) –> Mg(OH)2(s)
State what you would observe when calcium chloride and sodium hydroxide are mixed, and write ionic equations for any reactions you observe
faint white precipitate: Ca2+(aq) + 2OH-(aq) –> Ca(OH)2(s)
State what you would observe when calcium chloride and sulphuric acid are mixed, and write ionic equations for any reactions you observe
faint white precipitate: Ca2+(aq) + SO42-(aq) –> CaSO4(s)
State what you would observe when magnesium chloride and sulphuric acid are mixed, and write ionic equations for any reactions you observe
no reaction
Describe a suitable test for sulphate ions in solution
Add dilute hydrochloric acid followed by barium chloride solution
A white precipitate will be observed
Explain how BaSO4 is used in medicine
BaSO4 is consumed in a “barium meal”; it absorbs X-rays and so its path through the digestive system can be tracked using X-rays
Explain how MgSO4 is used in medicine
MgSO4 is consumed in order to treat Mg deficiency
Write an equation for the reaction between magnesium hydroxide and hydrochloric acid
explain a useful application of this reaction
Mg(OH)2(s) + 2HCl(aq) –> MgCl2(aq) + 2H2O(l)
used to treat indigestion caused by excess stomach acid
Write an equation for the reaction between calcium hydroxide and hydrochloric acid
explain a useful application of this reaction
Ca(OH)2(s) + 2HCl(aq) –> CaCl2(aq) + 2H2O(l)
used to neutralize acidic soils
Write an equation for the reaction between calcium oxide and sulphur dioxide
explain a useful application of this reaction
CaO(s) + SO2(g) –> CaSO3(s)
used to remove SO2 from factory chimneys
Write an equation for the reaction between calcium carbonate with sulphur dioxide
explain a useful application of this reaction
CaCO3(s) + SO2(g) –> CaSO3(s) + CO2(g)
used to remove SO2 from factory chimneys
Explain the use of magnesium in the extraction of titanium from TiCl4
The Mg reduces the TiCl4 to Ti by the reaction TiCl4 + 2Mg –> Ti + 2MgCl2
reducing agent
By what name are the elements F2, Cl2, Br2 and I2 collectively known?
halogens
By what name are the ions F-, Cl-, Br- and I- collectively known?
halides
State and explain the trend in electronegativity of the Group 7 elements
decreases down group
more shells
bonding electrons more shielded from nucleus
atom less able to attract bonding electrons to itself
State and explain the trend in boiling point of the Group 7 elements
increases down group
molecules have more electrons/larger surface area
so stronger Van der Waal’s forces
so more energy required to separate the molecules
Explain why the halogens are all oxidizing agents and state and explain the trend in oxidizing ability of the halogens
they have only seven electrons in the outer shell so can act as electron acceptors and become halides
Oxidising ability decreases down group
more shielding
So the incoming electron is less strongly attracted to the nucleus
Explain why the halides are all reducing agents and state and explain the trend in reducing ability of the halides
they can lose electrons to become halogens
reducing ability increases down group
more shells means more shielding
So electrons can be more easily lost from the outer shell
Predict whether or not a reaction would take place between SODIUM CHLORIDE AND IODINE.
If a reaction does take place, state what you would observe and write an ionic equation for the reaction taking place
no change
stays brown
Predict whether or not a reaction would take place between SODIUM IODIDE AND CHLORINE.
If a reaction does take place, state what you would observe and write an ionic equation for the reaction taking place
brown solution
Cl2(aq) + 2I-(aq) –> 2Cl-(aq) + I2(aq)
Predict whether or not a reaction would take place between SODIUM BROMIDE AND IODINE.
If a reaction does take place, state what you would observe and write an ionic equation for the reaction taking place
no change; stays brown
Predict whether or not a reaction would take place between SODIUM IODIDE AND BROMINE.
If a reaction does take place, state what you would observe and write an ionic equation for the reaction taking place
brown solution
Br2(aq) + 2I-(aq) –> 2Br-(aq) + I2(aq)
Predict whether or not a reaction would take place between POTASSIUM CHLORIDE AND BROMINE.
If a reaction does take place, state what you would observe and write an ionic equation for the reaction taking place
no change; stays orange
Predict whether or not a reaction would take place between POTASSIUM BROMIDE AND CHLORINE.
If a reaction does take place, state what you would observe and write an ionic equation for the reaction taking place
yellow/orange solution;
Cl2(aq) + 2Br-(aq) –> 2Cl-(aq) + Br2(aq)
write a half equation for this reaction:
I- to I2
2I- –> I2 + 2e
write a half equation for this reaction:
Br- to Br2
2Br- –> Br2 + 2e
write a half equation for this reaction:
H2SO4 to SO2
H2SO4 + 2H+ + 2e –> SO2 + 2H2O
write a half equation for this reaction:
H2SO4 to H2S
H2SO4 + 8H+ + 8e –> H2S + 4H2O
Chloride ions cannot reduce concentrated sulphuric acid.
Bromide ions reduce concentrated sulphuric acid to sulphur dioxide.
Iodide ions reduce concentrated sulphuric acid to hydrogen sulphide.
Explain these observations in terms of the relative reducing ability of the halides
Cl- is the weakest reducing agent and I- is the strongest reducing agent
Reducing power increases down the group; more shells and more shielding mean that the attraction between the outermost electrons and the nucleus is weaker and the species is a better electron donor
Cl- cannot reduce H2SO4
Br- reduces S in H2SO4 from +6 to +4
I- reduces S in H2SO4 from +6 to -2:
Write an equation to show the reaction between Iodide ions and concentrated sulphuric acid
H2SO4 + 2H+ + 2Br- –> SO2 + Br2 + 2H2O
Write an equation to show the reaction between Bromide ions and concentrated sulphuric acid
H2SO4 + 8H+ + 8I- –> H2S + 4I2 + 4H2O
10) Chloride ions react with concentrated sulphuric acid to give hydrogen chloride gas. Write an equation for this reaction and show that it is not a redox reaction
H2SO4 + Cl- –> HSO4- + HCl
The oxidation number of S is +6 in both reactant and product
Write an equation to show the reaction between chlorine and water to make chloric (I) acid
State what is oxidized and what is reduced in this reaction
State an application of this reaction
Cl2 + H2O == HCl(aq) + HClO(aq)
Cl is both oxidised (from 0 to +1) and reduced (from 0 to -1)
this is used to sterilise water; HClO is a sterilising agent
State what happens when chlorine is added to water in the presence of bright
sunlight
State what is oxidized and what is reduced in this reaction
2Cl2 + 2H2O –> 4HCl + O2
Cl is reduced (from 0 to -1) and O is oxidized (from -2 to 0)
Explain why chlorine is added to the water supply
Chlorine is added to the water supply to kill harmful bacteria (ie to sterilize the water)
State one advantage and one disadvantage of adding chemicals to the water supply
Adding chemicals to the water supply can have health benefits by killing harmful toxins or providing important nutrients.
The chemicals added to the water supply can themselves be toxic to some people and they take away the right of the individual to choose whether to add chemicals to their water
Write an equation to show the reaction between chlorine and sodium
hydroxide to make sodium chlorate (I)
State what is oxidized and what is reduced in this reaction
State an application of this reaction
Cl2 + NaOH –> NaCl(aq) + NaClO(aq) + H2O
Cl is both oxidised (from 0 to +1) and reduced (from 0 to -1)
this is used to make bleach
what is the test for OH-
NH4CL and warm
produces pungent smell
what is the test for Mg2+
aq NaOH
thick white ppt formed
what is the test for Ca2+
aq NaOH
faint white ppt formed
what is the test for Sr2+
H2SO4
faint white ppt formed
what is the test for Ba2+
H2SO4
thick white ppt
what is the test for NH4+
NaOH and warm
produced pungent smell
Test for H+
Na2CO3
effervescence
