module 3 ppqs

Question 1

7) why does the second ionisation energy of oxygen have a greater value than the first ionisation energy of oxygen?

Answer 1

• O+ ion is smaller than O atom
• there is less electron-electron repulsion

Question 2

7) state and explain the trend in the boiling points of chlorine, bromine and iodine

Answer 2

• boiling point increases down the group
• stronger london forces
• more energy needed to break london forces

Question 3

7) explain the decrease in atomic radii across the period from Na to Cl [3]

Answer 3

• nuclear charge increases
• shielding remains the same
• greater attraction

Question 4

10) why does the use of cataylsts reduce energy demand and benefit the environment?

Answer 4

• lower temperatures
• less fossil fuels
• reduces carbon dioxide emissions

Question 5

10) describe and explain the change in rate of reaction during the first X seconds of an experiment [2]

Answer 5

• rate of reaction decreases AND reactants are used up
• less frequent collisions

Question 6

10) draw a boltzmann distribution model to explain how rate of reaction is affected by temperature [3]

Answer 6

1. labels: number of molecules (y) energy (x)
2. curve starts within one small square of origin, curve does not touch x axis at high energy, curve does not increase by more than one small square at higher energy
3. higher T curve to the right and and least 1 square lower than lower T max

Question 7

9) explain in terms of bond breaking and bond forming, why a reaction can be exothermic [1]

Answer 7

more energy is released by forming bonds than energy required when breaking bonds