Inorganic Flashcards
Trend going down gp2
Atomic radius increases (more shells)
First Ionisation Energy decreases (easier to lose e-)
Melting point decreases (weaker metallic bonding)
Group 2 reaction w distilled water
Metal + water —> metal hydroxide + Hydrogen gas
X (s) + 2H2O (l) —> X(OH)2 (aq) + H2 (g)
Trend in reactivity w water down group 2
Reactivity increases downwards as outer electrons easier to lose:
- Be doesn’t react w water
- Mg reacts very slowly
- Ca steady reaction
- Sr and Ba react quickly
Group 2 reaction w steam
Group 2 Metal + steam —> metal oxide + Hydrogen gas
X(s) + H2O (g) —> XO(s) + H2 (g)
Solubility of group 2 hydroxides down group
Solubility increases going downwards;
Gp2 hydroxides have larger metal ions going down group
So the lattice energy in ionic compound weakens down
So ion dissociation increases
Mg(OH)2:
solubility, appearance and uses
Sparingly soluble
Dissolves to form a weak basic solution (low conc of OH- ions)
White solid
Used as antacids to neutralise stomach acid
Metal hydroxide + HCl
Metal hydroxide + HCl —> metal chloride salt + water
x(OH)2 (aq) + 2HCl (l) —> xCl2 (aq) + 2H2O (l)
Ba(OH)2
Solubility, appearance, and uses
Highly soluble
Dissolves readily in water to produce strong basic solution
White solid that dissolves to give clear, colourless solution
Used for laboratory analysis like titration
Group 2 sulfates solubility trend down group 2
Solubility decreases going downwards
As more white ppt formed readily when cation size increases
BaSO4 is completely insoluble
Test for presence of sulfate ions
- Add a few drops of HCl
(Removes any interfering ions that could give a false positive like carbonate ions) - Add a few drops of dilute BaCl2 solution
(Reacts w sulfate ions to form BaSO4) - if sulfate ions present white insoluble ppt will form
measuring the rate of reaction:
Mg ribbon with HCl
set up a rubber bung with a delivery tube that connects to a gas syringe (Held by a clamp)
add 45cm3 of 1moldm-3 HCl into a conical flask
add a 3cm long magnesium ribbon into the solution
quickly cap the bung onto the conical flask and immediately start stopwatch
record the volume of gas in the syringe every 15 sec
trend across the periodic table: atomic radius
(left to right)
atomic radius decreases
as more protons but same number of shells
so increasing nuclear charge
pulling outer electrons closer into nucleus
trend across a period: first ionisation energy
increases across a period
as more protons but same number of shells
so strong nuclear charge
harder to remove an outer electron
melting point down group 2
(+ explain the exception)
decreases down the group
down the group the metal ions get bigger
increasing the distance between the positive nucleus and the negative delocalised electrons
weak es forces of attraction
so lower melting point
Mg is the exception as it has a different crystal structure so it has a lower mp than expected
barium meals
BaSO4 is completely insoluble
used in x rays for medical imaging
coats stomach tissues to show up on xray
Extraction of Titanium using Mg
- titanium ore (TiO) is heated w carbon in Chlorine gas stream to form (TiCl4)
- TiCl4 is purified by fractional distillation
- TiCl4 is reduced by Mg in a 100*C furnace
TiCl4 (g) + 2Mg (l) –> Ti (s) + 2MgCl2 (l)
Removing sulfur dioxide from flue gas
- CaO or CaCO3 can be reacted with the acidic SO2 in flue gas
CaO (s) + 2H2O (l) + SO2 (g) –> CaSO3 (s) + 2H2O (l)
CaCO3 (s) + 2H2O (l) + SO2 (g) –> CaSO3 + 2H2O (l)
+ CO2 (g)
melting point across period 3
increases from Na to Si and then decreases from from Si to Ar
(beginning of trend across period 3)
Na, Mg and Al
trend in mp
melting point increases
as more protons but same shells
so stronger electrostatic forces of attraction between positively charged nucleus and delocalised electrons
so stronger metallic bonding
bonds require more energy to break
so melting point increases from Na to Mg
(middle of trend across period 3)
Si
trend in mp
(middle of period 3)
Si is macromolecular (tetrahedral structure)
has strong covalent bonds between all atoms
so has the highest mp in period 3
(end of trend across period 3)
P, S, Cl, Ag
trend in mp
(explain the exception)
(end of period 3)
P4, S8, Cl2, Ar
melting point decreases
all molecular substances
van der waals forces decreases
as the naturally existing molecule size decreases
(S8 is bigger than P4 so its melting point is a big higher, deviating from the decreasing trend)
First Ionisation energy
energy needed to remove one mole of electrons
from one mole of an atom in its gaseous state
to form 1 mole of a 1+ gaseous ion
trend in first ionisation energy across period 3
(explain the exceptions)
FIE increases across the period
more protons but same number of shells
so increasing nuclear charge
stronger efa attraction between electrons and positive nucleus
so harder to remove 1 mole of electrons from an atom
exception:
- Aluminium: outer electron is in 3p, which is a higher energy orbital and further away from the nucleus. Giving it a lower FIE than Mg before it
- Sulfur: has a paired orbital, which experiences repulsion. Making the electron easier to remove than phosphorus before it
flourine at room temp
appearance
exists as a pale yellow gas
colourless in solution (as become HF gas)
