Group 1 and 2 reactions Flashcards
How does reactivity change down the groups?
Increases down because to react, they lose outer shell electrons
Due to reasons of IE decreasing down, less energy is needed to lose electrons so increases down
How does the ionisation energy change down the group?
Decreases because the number of electrons increase thus fill up more shells. This causes more electron electron repulsion and increases atomic radii which decreases nuclear force
How does the melting point change as you go down the group?
Decreases because of the increase in ionic radii causing the delocalised electrons to experience less nuclear attraction
Group 2 + water produces?
A metal hydroxide and hydrogen
Exception to group 2 + water reaction
Beryllium = doesn’t react but can react with steam only
Magnesium = can react with steam and water (but with water very slightly)
What does magnesium + steam produce?
Magnesium oxide and hydrogen
Vigorously
What does magnesium + water produce?
Magnesium hydroxide + hydrogen
Quite slowly
Weakly alkaline solution because Mg(OH)2 is not that soluble in water
How does calcium + water react?
Moderately, produces calcium hydroxide and effervescence (hydrogen)
Slightly alkaline solution because is slightly soluble in water
How does strontium and water react?
Reacts rapidly, produces strontium hydroxide and a lot of effervescence (hydrogen)
Alkaline solution because quite soluble in water
How does barium react with water?
Barium hydroxide and hydrogen is produced (effervescence) which reacts very vigorously
Alkaline solution because is soluble in water
What does group 2 and oxygen react to form?
Group 2 metal oxide
(Solid white)
When group 2 reacts with oxygen, what is reduced?
The oxygen because it gained 2 electrons
When group 2 reacts with oxygen, what is oxidised?
The metal because it loses 2 electrons to form a positive metal ion in the metal oxide compound
Does beryllium oxide exist?
Yes
Are oxides bases?
Yes and because of the fact that solubility increases going down the group, they are of increasing alkaline strength going down
Does beryllium hydroxide exist?
No beryllium does not react with water
Does beryllium oxide dissolve in water?
No so does not act as a base
Why does the pH of dissolved metal hydroxide/ oxides increase going down the group?
Because the solubility increases going down the group
And so concentration of OH- ions releasing increases = alkaline solution
Metal oxide + water
Produces just the metal hydroxide corresponding and NO effervescence
Metal hydroxide + water
From the solid metal hydroxide precipitate to aqueous metal hydroxide
What is milk of magnesia?
Magnesium hydroxide
Why is milk of magnesia milky?
Because it’s very insoluble do forms white precipitate
Metal oxide (basic pH) with dilute acid reaction
Produces aqueous metal salt eg calcium chloride and water
Metal hydroxide (basic pH) with dilute acid reaction
Produces aqueous metal salt and water
Solubility trend of metal sulfates?
The solubility decreases down the group unlike hydroxides so beryllium sulfate most soluble
What does the solubility of metal compounds depend upon?
The charge of the anion
OH- has 1- charge so solubility increases down the group
SO4 2- has 2- charge so solubility decreases down the group
Thermal decomposition
When a substance breaks down on heating
How can we test for barium ions? (Other than flame test)
Add compound that might have barium into sulfate solution
White propitiate forming indicates barium ions present because it is the most insoluble in sulfate solution
How to test for mg ions other than flame test
React compound with dilute sodium hydroxide to form magnesium hydroxide which is insoluble in water so white precipitate would be formed
Barium sulfate uses
A barium meal to coat oesophagus so when X-rays are absorbed, you can see the digesting tract as if it were bone to check for problems = photopaque
Insolubility allows barium sulfate to be suspended and picked up on
Magnesium hydroxide uses
Helps with indigestion (milk of magnesia precipitate)
Neutralises acid stomach due to being weakly alkaline solution (save to use)
Calcium hydroxide uses
Used as slaked lime to neutralise pH of soil (which was acidic) for specific crop growth
Titanium extraction
Titanium exists as titanium oxide then titanium chloride
Where magnesium reduces titanium to produce titanium
Removal of SO2
Using calcium carbonate to form calcium sulphite from sulfur dioxide
Why does the reaction with magnesium and water slow down?
Magnesium is coated with a layer of magnesium hydroxide so reaction stops after a while
As the solubility of hydroxides increase down the group what happens?
Less solid precipitate remains and more dissolves thus more solution formed
What slows down the reaction of sulfuric acid and metal (barium, strontium etc)
Barium/strontium sulfates which coats the metal and therefore stops reaction
Reaction of metals with dilute nitric acid
Produces hydrogen and a metal nitrate
Hydrogen in acid reduced to gas
Metal oxides oxidised to ions
Magnesium in water observations
Slight bubbles produced on the surface
Floats on surface of water
Before testing reactions of magnesium, what should be done?
Use sandpaper to remove coat of magnesium oxide which will react with substances as well but at different rates
Metal vs metal oxides vs metal hydroxides reactions with acid
Metal produces salt and hydrogen
Metal oxide produces salt and water
Metal hydroxide produces salt and water
What increases the pH thus alkaline solution of metal hydroxide solutions?
More Free hydroxide ions as a result of the metal hydroxides increasing in solubility
Metal oxides act as…
Bases because they accept H+ ions when reacting with water to form metal hydroxides
Observations of reacting metal with water
Fizzing which gets more vigorous down group
Increasing alkaline solution down group
Solution gets increasingly hotter down group
Less precipitate formed down group
What is lime water?
Calcium hydroxide
What is lime water?
Calcium hydroxide
Dissolving metal hydroxides
Dissociates into metal ion and hydroxide ions
More hydroxide ions due to more soluble metal hydroxide = more alkaline solution
Dissolving metal hydroxides
Dissociates into metal ion and hydroxide ions
More hydroxide ions due to more soluble metal hydroxide = more alkaline solution
