Inorganic chem and periodic table - Topic 4 Flashcards
what is thermal decomposition
the name of a reaction in which a compound decomposes on heating
what do acids and metals make
hydrogen gas and a salt (a metal compound)
what do acids and bases make (neutralisation reaction)
salt and water
why do all the reactions between acids and bases make water
as the hydrogen ions react with the hydroxide ions to form water
supporting equation
OH-(aq) + H+(aq) ——> H20
what do acids and carbonates make
salt water and carbon dioxide
what are ionic precipitation reactions
a reaction which produces a solid precipitate on mixing two solutions containing ions
solubility table
to revise this better draw a table with one side being what is soluble in water and the other being whats insoluble in water
what are soluble:
- all acids
- calcium, sodium and potassium hydroxide - HOWEVER OTHER METAL OXIDES AND HYDROXIDES ARE INSOLUBLE (NOT SOLUBLE)
- carbonates of sodium and potassium -HOWEVER ALL OTHER CARBONATES ARE INSOLUBLE (NOT SOLUBLE)
- all nitrates
- all chlorides - HOWEVER SILVER CHLORIDE AND LEAD CHLORIDE ARE INSOLUBLE (NOT SOLUBLE)
- all sulfates - HOWEVER BARIUM SULFATE AND LEAD SULFATE ARE INSOLUBLE (NOT SOLUBLE)
- all sodium, potassium and ammonium salts
what does the solubility table explain
if the compound is soluble in wate then it is an aqueous but if it isnt then it is a solid
what are the changes to the atoms down the group in alkali metals
- the charge of the nucleus increase
- the atomic radius increases as there is an increase in the number of shells
- the force of attraction decreases
- the nuclear charge stays the same as its always plus 1
What happens in reactions with alkalis and water
- they all form hydroxides with water and hydrogen
- lithium gives off steam with bubbles of hydrogen
- sodium melts to form a shiny bead that skates on the surface of the water
- potassium catches on fire and burns with a lilac flame
Reactions with metals and chlorines
the all form colourless ionic metal chlorides
what is the trend of solubility down metal hydroxides
the solubility increases as you go down a group
why are hydroxides strong bases
as they are fully ionised in water, giving solutions of hydroxide ions
why do carbonates produce alkaline solutions when dissolved in water
as the carbonate ions remove the h+ ions from water molecules to form hydrogencarbonate ions and hydroxide ions, and these hydroxide ions make the solution alkaline
In a chemical test what proves the presence of hydroxides
white solids
In a chemical test what would group 1 nitrates look like
white crystalline solids
what does the thermal decomposition of group 1 NITRATE form AND whats the exception
a NITRITE and oxygen
e.g
2KNO3 —–> 2KNO2(s) + O2 (g)
EXCEPT LITHIUM as it decomposes into the oxide, nitrogen dioxide and oxygen
explain why sodium and potassium are used as chemical reagents
- their ions are inert so act as spectator ions
- they are the most soluble in water, including their hydroxides and carbonates compared to to other metal hydroxides and carbonates which are insoluble
- they are colourless in aqueous solutions so do not interfere with other colour changes
flame colours of GROUP 1 METALS
lithium - bright red
sodium - bright yellow
potassium - lilac
why does compounds containing sodium not burn during a flame test
as the energy from the flame excites the outer electrons of the sodium ions, raising them to higher energy levels, so the atom then emits the characteristic of a yellow light as the electrons drop back to lower energy levels
Trend of solubility in group 2
Decreases as you go down the group
Why does the reactivity increase as you go down alkaline earth metals (group 2)
As the first and second ionisation energy decreases as the atomic radius increases and the number of inner electron shells increase as you go down the group, so there is a weaker attraction between the nucleus and outer electrons as you go down the group so the first and second ionisation energies decrease as less energy is required to remove the outer 2 electrons causing the reactivity to increase
How does Mg, Ca and Ba react with oxygen
- They all form a white ionic oxide (which are solids)
- Mg burns with oxygen to form a bright white flame and a white solid magnesium oxide
- calcium burns with a yellow flame and forms a white solid calcium oxide
- barium burns with a green flame to form a peroxide BaO2 (which is also white)
How do alkaline earth metals (group 2 metals) react with water
- produces the alkaline metal hydroxides and hydrogen gas
- the rate of reaction increases as you go down the group
- mg reacts slowly to form Mg(OH)2 and hydrogen
How do alkaline earth metals (group 2 metals) react with chlorine
- it forms a metal chloride (and nothing else)
Why does the thermal stability of group 2 carbonates and nitrates increases as you go down the group
- as you go down the group the atomic radius increases, causing the size of the ion to increase so it will have a lower charge density, this decreases the polarising power of the metal ion as the low charge density makes it harder for the metal ion to attract the bonding electrons in carbonate/nitrate ion, so the electron cloud is not easily distorted so the bonds require a higher temperature to break.
what is a basic oxide
a metal oxide which can react to form salts and water by acting as a base by taking the hydrogen ion from the base
what do group 2 metals and acids form
salt and water
as the group 2 metals are basic oxides
What do group 2 metal oxides and water form
A metal hydroxide