Bonding

Question 1

Name the type of bond formed between N and Al in H3NaCl3 and explain how it is formed

Answer 1

Dative covalent bond and it is a shared pair of electrons where both come from the NH3

Question 2

why is nitrogen oxide covalent

Answer 2

As there is a small electronegativity difference between them
So can’t be ionic

Question 3

Of2 has a small electroneg difference so what type of crystal is it

Answer 3

Simple/ molecular

Question 4

State the type of crystal structure shown by titanium

Answer 4

Its a metal so metallic structure. If ever unsure go with lattice would work for ionic and metallic if its covalent just write covalent

Question 5

Why can titanium be hammered into objects with different shapes that can have similar strengths

Answer 5

As they (metals) have layers of atoms which can slide over each other meaning they are malleable

Question 6

I) suggest why these objects have similar strengths

Answer 6

(Strong) (metallic) bonding re-formed / same (metallic) bonding / retains same (crystal) structure / same bond
strength / same attraction between protons and delocalised electrons as before being hammered

Question 7

Fluorine reacts with bromine to form liquid bromine trifluoride what type of bonding is this and how is it formed

Answer 7

Covalent as 2 non metal, it is a shared pair of electrons one from br one from f

Question 8

The melting point of sodium chloride is much higher than that of sodium metals, what can be deduced from this info

Answer 8

That the ionic bonding in nacl is greater and requires more energy to be broke than sodiums metallic bonding

Question 9

Describe the bonding in a crystal of iodine (low mp) i2 and what crystal type is it

Answer 9

Van der waals forces
covalent and weak low mp
Its molecular

Question 10

The heat energy needed to vaporise smth is much greater than the heat energy needed to melt it. Why

Answer 10

As to vaporise them all of the bonds must be broken

Question 11

Predict the type of crystal structure of mgo which has a high mp

Answer 11

High mp so ionic

Question 12

Why is graphite soft

Answer 12

As there are weak imf’s weak van der waal forces between the layers

Question 13

State the meaning of the term electroneg

Answer 13

The atoms ability to withdraw a PAIR of electrons towards itself in A COVALENT BOND

Question 14

State how two carbon-carbon atoms form a carbon-carbon bond in GRAPHANE

Answer 14

Shared pair of electrons, one from each atom

Question 15

Explain why iodine vaporises when heated gently

Answer 15

As van der waals forces between molecules which are easily broken

Question 16

Predict the shape of and the bond angle of the complex rhodium ion (RhCl4)2-

Answer 16

Tetrahedral 109.5

Question 17

Which molecule does not have a permenant dipole. Ch3cl, chcl3, chcl2f or cf4

Answer 17

Cf4 doesn’t have one, low electroneg difference. and linear so dipoles cancel out

Question 18

Which of these does not contain any delocalised electrons,
Polypropylene
Benzene
Graphite
Sodium

Answer 18

Polypropylene

Question 19

Suggest one reason why electron pair repulsion theory cannot be used to predict the shape of a (Cocl4) 2- ion

Answer 19

As there are too many electrons in the orbitals. doesnt really work for electrons within the d orbital

Question 20

What is the bonding in iodine

Answer 20

Covalent between atoms

Question 21

Why is heat required to melt an iodine crystal

Answer 21

As bonds between molecules must be broken

Question 22

What property of an atom causes it to be polar

Answer 22

Electronegativity.

Question 23

Explain how the electron pair repulsion theory can be used to deduce the shape of the bond angle in PF3

Answer 23

P has 5 electrons in its outer shell, 3 from fluorine making a total of 8 electrons. There are 3 bond pairs and one lone pair. the electron pair repulsion theory states that electron pairs REPEL to be as far away as possible. Lone pairs repel more than bonded pairs, in conclusion forming a trig pyr shape with a bond angle of 107 degrees.

Question 24

For a question comparing na nabr and naI what do you have to include

Answer 24

Talk about how na metallic bonds etc and THAT IS HAS A LATTICE STRUCTURE and nabr ionic stronger efoa stronger bonds opp ions and then how it is smaller than iodine so higher charger den BUT ALSO THAT NABR IS ALSO A LATTICE STRUCTURE

Question 25

How are van der waals forces created

Answer 25

Movement of electrons in the fist molecule so all of the negative side, temporary dipole in this FIRST MOLECULE which induces another dipole in a NEIHBOURING MOLECULE and attraction of delta pos and delta neg.- difference in electroneg leads to bond polarity

Question 26

Why is phosphine insoluble in water

Answer 26

As it does not form hydrogen bonds with water (weaker imfs so cant be surrounded by water molecules and vdws cant break hydrogen bonds to fit in w them)

Question 27

Why is the melting point of I2 bigger than HI (6 marks)

Answer 27

I2 and HI are both molecular, intermolecular forces hold the molecule together. These are weak in both molecules so their melting points are both low. Iodine is a bigger mol than HI so it has more electrons so its vdw’s are stronger so more en needed ot break them so the mp is higher than HI eventhough they show permenant dipole dipole interactions the vdws in iodine are stronger though generally d-d would be stronger. So more energy is needed to break the imfs between the mols of iodine so its mp is higher.

Question 28

Explain how the value of the cl-al-cl bond angle. In ALCL3 changes (if at all) the formation of the compound H3NAICl3 (baso nh3)

Answer 28

In alcl3 the bond is 120 degrees between all the bonds and when you add NH3 to it it becomes tetrahedral around the Al so the bond angle is now 109.5

Question 29

what does adding cl do to water and why might it be a disadvantage

Answer 29

Kills bacteria, wasteful as most potable water isn’t used for drinking and some people might not like the taste

Question 30

If we have CH3CL whats its shape

Answer 30

4 bonds so tetra but weird so distorted tetrahedral or just call it tetrahedral

Question 31

Suggest a value for the H-O-O bond angles

Answer 31

94-105.5 degrees

Question 32

An aluminium chloride molecule reacts with a chloride ion to form the AlCl4- ion. Name the type of bond formed in this reaction, explain how this type of bond is formed in the AlCl4- ion

Answer 32

Dative covalent and electron pair from cl- donated to Al(Cl3)

Question 33

There are two lone pairs of electrons on the oxygen atom in a molecule of OF2 explain how the lone pairs of electrons on the oyxgen atom influence the bond angle in oxygen difluoride

Answer 33

Lone pairs repel more than bonding pairs bond angle will be lower than regular tetrahedral angle bond angle of 103-106 degrees

Question 34

Explain why nickel is ductile

Answer 34

Has sheets of atoms which can slide over each other or layers of atoms or whatever

Question 35

Ice- describe why melting point isnt that high but higih

Answer 35

Covalent bonds between atoms in water and hydrogen bonding exists between water molecules. Less energy is required to break hydrogen bonds in ice to form seperate water molecules

Question 36

What is a ionic lattice

Answer 36

Regular repeating arrangement of oppositely charged ions

Question 37

Explain why magnesium has a stronger mp than sodium

Answer 37

Magnesium has a higher nuclear charge so attracts delocalised electrons more strongly.

Question 38

Describe lone pair bonded pairs for 2 2 bent

Answer 38

Lone pairs repel more than bonded pairs and will arrange themselves to be as far away as possible so the bond angle is REDUCED from 109.5 to 104.5 BASIcally its reduced from a tetrahedral w 4 bond pairs to 2 and 2

Question 39

Why does distillation allow the separation of propanal from propanoic acid and propan-1-ol

Answer 39

As the aldehyde has dipole dipole forces whereas the alcohol and the carboxylic acid contain hydrogen bonds.

Question 40

2 ways of maximising the yield of propanal by the reac mixtur

Answer 40

Keep the temp below 97 (as then the other two wont form, thats the boiling point of the second one and the third ones way higher at 146 so if the temps kept at below 97 the other ones wont seperate and you will max your yield of propanal Also- by cooling the distillate. (Ensuring none is lost)

Question 41

Suggest why graphene is an excellent conductor of electricity

Answer 41

Contains delocalised electrons which are able to move within the structure/crystal

Question 42

Explain how vdw forces arise

Answer 42

Uneven distribution of charge causes a temp dipole in one molecule and this induces another temp dipole in a neighbouring mol And there is an induced temporary attraction

Question 43

explain how permenant dipole dipole forces arise between two molecules

Answer 43

differences in electronegativity leads to bond polarity

Question 44

when does something not have perm dip dipo

Answer 44

if its linear or like b3f3 because they cancel out

Question 45

why cant the vsepr theory be used for complex ions

Answer 45

bc only really works for s and p subshells, too many electrons in the d subshell

Question 46

in terms of structure and bonding, explain why the boiling point of bromine is different from that of magnesium. suggest why magnesium is a liquid over a much greater temp range compared to bromine

Answer 46

bromine is molecular, mg is metallic. metallic bonds stronger. br has weak van der waals. mag has a much greater liquid range because the forces of attraction in liquids are stronger

Question 47

explain how the value of the cl-al-cl bond angle in alcl3 changes if at all on the formation of the compound h3naIcl3

Answer 47

Aluminium is now surrounded by 4 electron pairs, is now tetrahedral. therefore the cl-al-cl bond would decrease from 120 degrees to 107-111 degrees in h3naIcl3

Question 48

cyclohexene is prepared by the dehydration of cyclohexanol using conc phosphoric acid as a catalyst. identify the factors that influence the bps and state why cyclohexane can be seperated from the mixture o

Answer 48

cyclohexene= vdw forces cyclohexanol has h bonds. phosphoric acid has h bonds. cyclohexene has the weakest intermolecular forces so can be seperated by fractional distillation ias it should boil offf first

Question 49

identify the condition that causes a bond in ccl4 to break

Answer 49

uv light and then the equation is ccl4-->ccl3 +cl radical

Question 50

Explain, in terms of electronegativity, why the boiling point of H2S2 is lower than H2O2

Answer 50

Electronegativity of S lower than O No hydrogen bonding between H2S2 molecules Or only van der Waals

Question 51

Suggest why the electronegativity of the elements increases from lithium to fluorine.

Answer 51

as nuclear charge increases w similar shielding

Question 52

Use the concept of electronegativity to justify why the acid strengths of ethanedioic acid and ethanoic acid are different

Answer 52

ge 1: difference in structure of the two acids • The acids are of the form RCOOH • but in ethanoic acid R = CH3 • whilst in ethanedioic acid R = COOH Stage 2: the inductive effect • The unionised COOH group contains two very electronegative oxygen atoms • therefore has a negative inductive (electron withdrawing)effect • The CH3 group has a positive inductive (electron pushing) effect Stage 3: how the polarity of OH affects acid strength • The O–H bond in the ethanedioic acid is more polarised / H becomes more δ+ • More dissociation into H+ ions • Ethanedioic acid is stronger than ethanoic acid

Question 53

the melting point of XeF4 is higher than the melting point of PF3 . Explain why the melting points of these two compounds differ. give the shape of the molecule and explain why each molecule has that shape and how that shape infleuces the forces that affects the mp

Answer 53

XeF4 has 4 bps and 2 lps Pf3 has 3bps and 1lp xef4 is a square planar pf3 is pyramidal in pf3 electron pairs repel to be as far away as possible and lp repel even more than bps xef4 has van der waals forces but pf3 has dipole dipole forces. the vdw in xef4 are stronger than dipole dipole in pf3 due to its larger mr. more electrons.

Question 54

why would a longer mol have stronger vdws

Answer 54

more electrons, stronger van der waals BETWEEN MOLECULES