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CH5 > P-block > Flashcards

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?

A

CaCO3(s)

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
Q

What lead compounds are insol and sol in water?

A

PbSO4 insol
PbCl2 sp sol
Pb(NO3)2 sol

25
Q

What happens when PbO is heated in NaOH?

A

Pb(OH)4 2- is formed as a colourless solution

26
Q

What chloride reacts with water vigorously? Why?

A

SiCl4

Due to Si being able to accept oxygen’s lone pair in its d orbital

27
Q

CCl4 does what with water?

A

Doesn’t react, forms an immiscible layer- no access to d orbitals

28
Q

What do you observe when SiCl4 comes into contact with water?

A

Reacts vigorously forming fumes of HCl and SiO2(s)

29
Q

What does PbCl2 do with HCl?

A

Dissolves in conc HCl to form PbCl4 2-

30
Q 
When lead(2)nitrate reacts with NaOH what happens?
What happens with excess NaOH?
A

White ppt of Pb(OH)2 formed

Redissolves in a colourless solution of Pb(OH)4 2- (aq)

31
Q

What happens when Cl- ions are added to Pb(NO3)2?

A

Forms white ppt of PbCl2 that is sol in hot, sparingly sol in cold and soluble in HCl

32
Q

Lead(2) nitrate and I-?

A

Bright yellow ppt of PbI2 formed (but sol in hot)

33
Q

What is Iodine at STP? And when heated?

And with starch?

A

Grey black solid
Purple fumes
Blue black

34
Q

Oxidising power trend in G(7)?

A

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
Q

Chlorine reacts with NaOH in two different ways- explain and give eqns

A 
Cold NaOH(aq) -> NaCl + NaClO + H2O (disproportionation)
Warm conc NaOH-> NaCl + NaClO3 + H2O
36
Q

Chlorine reacts with water-

A

Cl2 + H2O-> ClO- + Cl- + 2H+

The ClO- is a powerful disinfectant (bleach) (water supplies) (inexpensive)

37
Q

ClO3 - is used as?

A

Effective weed killer
Powerful oxidising agent
Explosive with organic materials :o

38
Q

What happens when conc sulphuric acid is added to NaCl?

A

Steamy fumes of HCl + NaHSO4

39
Q

What happens when conc sulphuric acid is added to NaBr?

A

Steamy fumes of HBr which acts as a reducing agent -> Br2 (red brown fumes) SO2 (choking gas) and steam

40
Q

What happens when conc sulphuric acid is added to NaI?

A

Steamy fumes of HI which is the strongest reducing agent-> I2 (purple fumes) H2S (rotten egg smell) steam and S (yellow solid)

41
Q

2 uses of F?

A

CFCs as aerosol propellant

PTFE as non stick frying pans

42
Q

4 uses of Cl?

A

ClO- sterilises drinking water
ClO3 - weed killer
PVC guttering
DDT pesticides

43
Q

2 uses of Br?

A

Silver bromide in photography

Dyes and medicines

44
Q

2 uses of I?

A

KI kept near nuclear plants to reduce conc of radioactive I in body
Antiseptic (I2 in ethanol)

CH5 (8 decks)

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