F332 Model Answers

Front 1

Explain how hydrogen bonds & instantaneous dipole-induced dipole bonds are formed.

Back 1

Hydrogen bonds:
1) Oxygen small & electronegative.
2) Attracted to hydrogen with a slightly positive charge.

Id-Id:
1) Electron movements in the molecules create an uneven distribution of the charge.
2) A dipole is induced in the neighbouring molecule leading to attraction.

Front 2

Explain why [ x ] is slightly soluble in water, but [ y ] is insoluble.

Back 2

[ x ] can form hydrogen bonds with water. Whereas [ y ] cannot form hydrogen bonds with water.

Front 3

Difference between carbon dioxide & silicon dioxide in terms of melting points, bonding & structure.

Back 3

Silicon dioxide is a giant covalent lattice whereas carbon dioxide is simple molecular. Therefore carbon dioxide has weaker intermolecular forces, bonds in silicon dioxide are stronger. So less energy in order to break the bonds of carbon dioxide.

Front 4

Explain why ______ has E/Z isomers.

Back 4

Rotation not possible around the C=C double bond.

It contains a C=C with two different groups on each carbon.

Front 5

Why pressure increases the rate of reaction.

Back 5

Particles are closer together. So therefore they collide more frequently and so this leads to more successful collisions per second.

Front 6

Explain why CFCs are not broken down in the troposphere and how CFCs contribute to the breakdown of ozone in the stratosphere.

Back 6

Not enough/too little energy in the troposphere to be able to break the bonds.

In the stratosphere the UV causes photodissociation

To form chlorine radicals.

These radicals catalyse the breakdown of ozone.

Front 7

How do the structures of HDPE & LDPE affect the strength of their instantaneous dipole-induced dipole bonds?

Back 7

LDPE has branches.

So therefore LDPE cannot pack closely so overall has less surface area.

This leads to weaker intermolecular forces.

So less energy is needed in order to break the bonds.

Chains of LDPE slide over each other more easily.

Front 8

Explain how the presence of ozone in the stratosphere benefits us.

Back 8

Ozone prevents/stops high frequency UV radiation from entering the atmostphere which could otherwise damage our cells.

Front 9

Describe & explain how the rate of a reaction varies under the different temperature conditions.

Back 9

The rate is greater when the temperature is higher.

At higher temperatures particles have more kinetic & vibrational energy and so ultimately move faster.

This leads to more successful collisions per second.

Front 10

Explain what is meant by ultraviolet dissociation of a molecule & how it occurs. Name the type of bond fission that is taking place.

Back 10

High frequency UV radiation

causes the bonds in a molecule to break/causes photodissociation and forms radicals.

Homolytic fission occurs/ bonds break homolytically.

Front 11

Explain why chlorine dioxide has a higher boiling point that chlorine, by referencing to their intermolecular forces/bonds.

Back 11

Chlorine dioxide has polar bonds

Chlorine dioxide forms permanent dipole-permanent dipole bonds

Whereas chlorine forms instantaneous dipole-induced dipole bonds

Which are much weaker than permanent dipole-permanent dipole bonds

So therefore chlorine overall requires less energy in order to break its bonds.

Front 12

Explain and describe the natural processes by which the ozone is formed in stratosphere.

Back 12

UV radiation causes the formation of oxygen radicals

These oxygen radicals react with O² forming the ozone.

Front 13

Risks of high frequency UV radiation.

Back 13

Damages skin cells

Damages eyes

Damages immune system

Affects the crops

Front 14

Explain how increased concentrations of carbon dioxide in the troposphere could be linked to global warming, saying where the energy comes from originally.

Back 14

Sun emits UV

Earth absorbs this UV which heats the Earth up

CO2 absorbs IR

Which causes the bonds to vibrate (more)

More CO2 means more radiation is then absorbed

This energy is transferred to kinetic energy that increases atmostpheric temperature