Rates and bonding cycle

How to answer questions on intermolercular force/ physical properties (4/5)

1. Identify

2. Compare

3. why

4. energy

Why does HCL have a higher boiling point that CH₄ (4)

1. HCL→ dipole- dipole and CH₄ → London

2. dipole-dipole forces are greater/stronger than London

3. Permanent polarity can connect immediately, whereas London must induce a dipole

4. more energy needed to boil HCL than CH₄

inter

• Hydrogen

• Dipole-dipole

• London

intra

• Covalent

• Ionic

• Metallic

London Forces

• non-permanent/induced/fluctuating dipoles

• The more electrons in an atom, the greater the magnitude of the fluctuating dipoles

• stronger in molecules/atoms with a lot of electrons

Dipole- dipole

• Permanent dipoles - have oppositely charged ends

• The oppositely charged ends attract each other with London Forces

• leading to a stronger attractive force

• spend time unequally- has a positive and negative side

• little electropositivity difference

Hydrogen Bonding

• NOF

• small high electronegativity

• has to involve H

How to answer collision theory questions?

1. How does the ( temperature, surface area (s), concentration ( aq), pressure (g), catalyst and the nature of reactant)

2. Link this change to the conditions for an effective collision (refer to the frequency of collisions, the correct orientation or the energy requirement) Does it increase/ decrease collision

3. How does this affect the number of effective collisions per unit time?

4. Increase/ decrease the reaction rate?

Concentration

1. An increase in concentration increases the number of particles per unit volume

2. More particles per unit volume and a higher frequency of collisions

3. Therefore, an increase in effective collisions

4. Increasing reaction rate

Surface Area

1. Increasing surface area means that there is a greater number of surface particles exposed to collisions

2. An increase in the frequency of collisions

3. therefore, an increase in the number of effective collisions per unit time

4. This leads to a higher reaction rate

Catalyst

1. A catalyst decreases the activation energy

2. More particles kinetic energy greater than or equal to overcome the lowered activation energy

3. thereforeincrease the number of effective collisions per unit time

4. This leads to a higher reaction rate

Nature of Reactant

1. The more reactive an element is, the smaller the activation energy

2. The lowered activation energy increases the frequency of effective collisions

3. This results in more effective collisions per unit time

4. Increase the reaction rate

temperature

1. A higher temperature means that the
   particles have a greater average kinetic energy

2. there is an increase in the number of collisions per unit time, (there is a greater proportion of particles with sufficient kinetic energy to overcome the activation energy)

3. There is therefore an increase in the number of effective collisions per unit time

4. This leads to a higher reaction rate

 

pressure

1. A higher pressure means that there are more particles per unit volume

2. There are more collisions per unit time

3. This results in more effective collisions per unit time

4. increasing the reaction rate