P-block Flashcards

0
Q

What electrons do Pb ions in their most stable state use?

A

Only p2 electrons

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1
Q

What is the inert pair effect?

Where does it occur?

A

The increased tendency for the s2 pair not to be used in the bonding on decent of the group.
In groups 3,4&5 the lower valencies (+2) become more stable as the group is descended.

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2
Q

What is the max covalency of period 2 and why?

A

Max covalency is 4 as they can only bond using s and p orbitals (s1 p3)
They have no d available

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3
Q

How does phosphorous bond in PCl5

A

It can promote a 3s electron to a 3d orbital, allowing 5 electrons to be available for bonding

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4
Q

What happens when NaOH(aq) is added to Al3+ (aq)

A

White ppt of Al(OH)3(H2O)3 is formed

OH- ions remove protons from complex to turn the H2Os to OH-s

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5
Q

What is formed when both Al and Al2O3 is added to NaOH?

A
Na(Al(OH)4) is formed
With H2(g) for Al and H2O for Al2O3
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6
Q

What does Al(aq) do when it acts amphotercially?

A

Liberates H2(g)

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7
Q

What happens when excess NaOH(aq) is added to Al(OH)3(H2O)3

A

White ppt redissolves and Al(OH)4 -

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8
Q

With which element does a similar thing occur when Al(aq) is added to NaOH? And with which element does this trend not occur?

A

Pb2+

Mg

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9
Q

When PbO is added to HCl two things can happen- explain

A
If warm (above 20°) forms PbCl2(aq)
If cool (below 20°) forms PbCl4(aq)
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10
Q

Why does AlCl3 tend to bond with group 5 elements?

A

It is electron deficient so forms coordinate bonds as G5 element donates lone pair to form a stable octet

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11
Q

What is an ionic liquid? Give 2 uses an 2 properties

A

An organic salt with mpt below 100° so are liquid over a wide temp range
Can replace volatile organic compounds as solvents and catalysts (eg polymerisation of alkenes)

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12
Q

Why are ionic liquids useful?

A

-Allows reactions to be performed under mild conditions
(Reduced energy costs, won’t thermally decompose reactants)
-immiscible in organic products so can be separated easily
-non volatile

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13
Q

Boron nitride exists in two forms and is-

A

Isoelectronic with carbon

Hexagonal and cubic forms

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14
Q

Compare Boron nitride and graphite

A
Both-
Layers of hexagonal rings with weak bonds between the layers
3 bonds with one unbonded p-orbital
Can be used as a lubricant 
Can form nanotubes
BN-
No delocalised electron (empty unbonded p-orbital) between layers
Insulator and inert
Used as reaction vessel
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15
Q

Compare boron nitride and diamond

A
Both-
cubic structures with 4 covalent bonds from each atom
Really hard 
High thermal conductivity 
Wear resistant
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16
Q

Why is CO a reducing agent and give an example

A

Readily loses electrons to return to +4 oxidation state
Can be used to extract metals from their ores
Fe2O3 +3CO -> 3CO2 + 2Fe

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17
Q

Give an example of why Pb4+ is interesting (with eqn)

A

Strong oxidising agent

PbO2+ 4HCl -> PbCl2 + Cl2 +2H2O

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18
Q

What happens when CO2 reacts with water?

A

Acidic solutions formed in equilibrium

HCO3- +H+ (CO3)2- + 2H+

19
Q

What is formed when CO2 reacts with NaOH?

A

Na2CO3 and water are formed if alkali is in excess

Forms NaHCO3 is CO2 is in excess

20
Q

What makes limewater milky?

21
Q

Why can’t you isolate Ca(HCO3)2

A

It will decompose to form CaCO3, CO2 and water

22
Q

What happens if excess CO2 is added to lime water?

A

Form colourless solution of Ca(HCO3)2 ions

23
Q

What two forms does lead(11)oxide exist as?

A

Yellow form and red form

24
What lead compounds are insol and sol in water?
PbSO4 insol PbCl2 sp sol Pb(NO3)2 sol
25
What happens when PbO is heated in NaOH?
Pb(OH)4 2- is formed as a colourless solution
26
What chloride reacts with water vigorously? Why?
SiCl4 | Due to Si being able to accept oxygen's lone pair in its d orbital
27
CCl4 does what with water?
Doesn't react, forms an immiscible layer- no access to d orbitals
28
What do you observe when SiCl4 comes into contact with water?
Reacts vigorously forming fumes of HCl and SiO2(s)
29
What does PbCl2 do with HCl?
Dissolves in conc HCl to form PbCl4 2-
30
``` When lead(2)nitrate reacts with NaOH what happens? What happens with excess NaOH? ```
White ppt of Pb(OH)2 formed | Redissolves in a colourless solution of Pb(OH)4 2- (aq)
31
What happens when Cl- ions are added to Pb(NO3)2?
Forms white ppt of PbCl2 that is sol in hot, sparingly sol in cold and soluble in HCl
32
Lead(2) nitrate and I-?
Bright yellow ppt of PbI2 formed (but sol in hot)
33
What is Iodine at STP? And when heated? | And with starch?
Grey black solid Purple fumes Blue black
34
Oxidising power trend in G(7)?
Decreases down group | Displacement reactions show this as -1 ox state of Cl- is more stable than -1 ox state of Br- and I-
35
Chlorine reacts with NaOH in two different ways- explain and give eqns
``` Cold NaOH(aq) -> NaCl + NaClO + H2O (disproportionation) Warm conc NaOH-> NaCl + NaClO3 + H2O ```
36
Chlorine reacts with water-
Cl2 + H2O-> ClO- + Cl- + 2H+ | The ClO- is a powerful disinfectant (bleach) (water supplies) (inexpensive)
37
ClO3 - is used as?
Effective weed killer Powerful oxidising agent Explosive with organic materials :o
38
What happens when conc sulphuric acid is added to NaCl?
Steamy fumes of HCl + NaHSO4
39
What happens when conc sulphuric acid is added to NaBr?
Steamy fumes of HBr which acts as a reducing agent -> Br2 (red brown fumes) SO2 (choking gas) and steam
40
What happens when conc sulphuric acid is added to NaI?
Steamy fumes of HI which is the strongest reducing agent-> I2 (purple fumes) H2S (rotten egg smell) steam and S (yellow solid)
41
2 uses of F?
CFCs as aerosol propellant | PTFE as non stick frying pans
42
4 uses of Cl?
ClO- sterilises drinking water ClO3 - weed killer PVC guttering DDT pesticides
43
2 uses of Br?
Silver bromide in photography | Dyes and medicines
44
2 uses of I?
KI kept near nuclear plants to reduce conc of radioactive I in body Antiseptic (I2 in ethanol)