Inorganic Chemistry and the Periodic Table Flashcards
Describe in basic terms, the appearance of Group 2 metals
- bright silvery solids
- when exposed to air, they combine with oxygen to form oxides as surface layers, which makes them appear dull
Trend in ionisation energies in group two
Ionisation energy decreases down group two
Although nuclear charge increases, one new quantum shell is added each time, which is at a higher energy level and also increases repulsion (shielding)
What type of ions are made in reactions with group 2 elements and whats the general trend in reactivity
M2+ ions
a general increase
What happens to group two elements when they are burned in air And the general equations for these reactants
For a bright flame usually
These reactions become more vigorous down a group
They usually form solids, which are oxides
2M + O2 -> 2MO
What two ions are formed in oxides of group 2
M+2
O-2
What has to happen to the group 2 elements to combine with chlorine gas?
What happens to reactiviy as we go down the group in this reaction
And what is the general equation for this reaction
Heated in the gas
More vigorous down the group
M+Cl2 -> MCl2
How do group two metal react with water
What is the trend with reactivity down the group
What is the general equation for these reactions
As we move down the group, they react with increasing vigour, which can be seen by increase in effervescence and hydrogen bubbles
M + 2H2O -> M(OH)2 (aq) + H2 (g)
What are the products of group 2 metals reacting with water
M2+
OH-
What is the difference between these two group 2 reactions with water and why
Ca(s) + 2H2O(l) -> Ca(OH)2 (s) + H2 (g)
<span>Ba</span>(s) + 2H2O(l) -> Ba(OH)2 (aq) + H2 (g)
difference in state symbols for the hydroxides
Barium hydroxides is soluable in water
What happens to a group 2 (magnesium) when heated with steam
Write an equation for this reaction
And describe an experiment for it
Rapidly forms M (magnesium) oxides and hydrogen gas, in a vigorus reaction
Mg(s) + H2O(g) -> MgO(s) + H2(g)
Hydrogen is formed is burned as it leaves the tube, as it is highly flammable
What is the general trend of reactivity moving down the group
increasing reactivity
Group 2 oxides are classed as what and why
In which reaction does this occur and write a general equation
Basic oxides
Because they can react with water to form alkalis
These reaction occur when oxides are added to water
MO(s) +H2O(l) -> M(OH)2(aq)
What amkes oxides with water alkaline
The formation of hydroxide ions
The pH value of the alkaline solution formed with oxides in water depneds on what
Relative amounts of oxides and water
different solubilities of the hydroxides
How does the test for Carbon dioxide link to reactions with group 2 oxides and water
And what ias the equation for this reaction
limewater is use to test for CO2
As a white precipiate forms in the presence
Limewater is a saturated aq solution of calcium hydroxide
Carbon dioxide reacts forming calcium carbonate, whcih is insoluable in water
CO2 + Ca(OH)2 -> CaCO3 +H2O
As carbon dioxide is bubbled through limewater, the amount of precipate
increases
What is milk of magnesia
indigestion remedy, acts as an antacid
saturated soluation of magnesium hydroxide mixed with extra solids of magnesium hydroxide
How does Milk of magnesia work
and the name the equation for the reaction
neutralises some of the hydrochloric acid
Mg(OH)2 + 2HCl -> MgCl2 + 2H2O
All of group 2 oxides and hydroxides (alkalis) react with acids to form
This type of reaction is
What would you observe in these reactions
salts and water
Neutralisation reaction
a white solid reacts to form a colourless solution
Reactions of oxides and hydroixdes with acids are endothermic or exothermic?
exothermic
What is the use of calcium hydroxide and agricuture
And write an equation for this reaction where HNO3 (nitric acid) is soil
farmers have used lime to control acidity so that a great yeild of crop can be obtained
Lime is mostly Calcium Hydroxide, and neutralises excess acidity in the soil
Ca(OH)2 + 2HNO3 -> Ca(NO3)2 + 2H2O
True or False, all group 2 nitrates and Chlordies are soluble
True
Does the solubility of Group 2 nitrates increase or decrease down a group
Increase
How would you test for sulfate ions in aq solution
adding a solution containing barium ions
(usually barium chloride/nitrate)
Any sulfate ion in the solution will react with the barium ions to form a white precipitate of barium sulfate
When testing for sulfate ions in a aq solution you use, barium nitrate/chloride and it forms barium sulfate
Write an equation for this
Ba+2 (aq) + SO42- (aq) -> BaSO4 (S)
What has to be present to stop other anions, (like carbonate ions) from forming a white precipiate with the barium ions, when you’re wanting to test for sulfates
Therefore what can be done to stop this
H+ ions
Dilute nitric acid or dilute hydrochloric acid
What is the purpose of barium sulfates in hospitals
Barium meals
Not posionous because it’s insolubale
It helps soft tissue to show up better on an X-rays, because of the dense white soilds
What is thermal stability
is a measure of the extent to which a compound decomposes when heated
If something doesn’t decompose at all, it is
Very thermally stable
If something completely decomposes as much as possible, it is
Not thermally stable
What is responsible for the melting temperture of a compound
ionic bonding
And the strength of these bonds will determine how easily the substance melts
How thermally stable are ionic compounds and why
Very
Ions change from being regularly arranged in a gaint lattice to moving freely in a liquid, however no decomposition occurs
What are the 3 differences between group 2 nitrates/carbonates and group 1 chlorides
1) Charge on group 2 ions (M2+)
2) Size (ionic radius) is smaller in group 2 cation (proton number)
3) Nitrates (NO3-) + Carbonates (CO32-) anions more complex than halogen ions (Cl-)
What do the 3 difference between group 2 Nitrates/Carbonates and Group 1 halogens (chlorides), to the thermal stability
When group 2 nitrates/carbonates are heated, they do not melt, they decompose, meaning a decreased thermal stability
Why does a group 2 metal, which is bonded to a larger , more complex nitrate ion, mean they can decompose
Nitrate ions can change into smaller, more stable nitrite ions (NO2-)or oxide ino (O2-) by decomposing and releasing oxygen gas and/or nitrogen dioxide gas
Why does a group 2 metal, which is bonded to a larger , more complex Carbonate ion, means they can decompose
they can change into smaller, more stable oxide ions (O2-) by decomposing and releasing CO2
Why does a group 2 metal, when bonded to a nitrate/carbonate ion, meaning it more likely to decompose, in terms of size and charge
Stabilities of the nitrate/carbonate anions are influenced by the charge and size of the cation present
The smaller, more highly charged cations (+) affect anions (-) more, due to greater charge density
What happens to the white soilds or group 1 and 2 nitrates when heated
When they are heated, they all decompose to nitrates/oxides, and give off nitrogen dioixde (brown fumes) and/or oxygen
When nitrates of group 1 and 2 are decomposed and they contain water of crystallisation, what will observed
Steam
Describe the lesser decompostion of a group 1/2 nitrate
No brown fumes
Metal Nitrate -> Metal nitrite + Oxygen
Describe the greater decompostion of a group 1/2 nitrate
Brown fumes are observed
Metal nitrate -> metal oxide + nitrogen dioixe + oxygen
What is the general trend in group 1 for lesser and greater decompostion
Lithium : brown fumes
Sodium - Caesium : now brown fumes
What is the general trend for lesser or greater decompostion of group 2 nitrates
Beryllium - Barium = brown fumes
Therefore greater decomposition
How does charge and size link to greater and lesser decompositon of group 1/2 nitrates
Cation has a 2+ charge, has greater decompostion
Cation has 1+ charge and a smallest ionic radius (Lithium) decomposes