Rates Of Reaction

Question 1

Increase pressure?

Answer 1

• when pressure of gas is increased, molecules are pushed closely together. The number of particles remain the same but space is less occupied
• means that there is an increased chance of the molecules colliding and more chance of successful collisions which increases R.O.R
• increasing the pressure decreases the volume the molecules have less space so more collisions per unit time

Question 2

Increasing temperature?

Answer 2

As temperature increases, the R.O.R increases
• the molecules have more K.E so they move faster
• there are more collisions
• therefore more chance of successful collisions so increases the rate

Question 3

Catalysts?

Answer 3

• speed up a reaction without being used up by providing a route requiring a lower Ea
• of the activation energy is lower, more particles will have energy greater than the Ea. so there will be a higher frequency of effective collisions which increases R.O.R

Question 4

Increasing concentration?

Answer 4

• at higher concentrations, there are more particles in a given volume meaning there are more particles to react so therefore an increase chance of collisions and will be a higher frequency of effective collisions

Question 5

Advantages of using catalysts?

Answer 5

• catalyst speed up reactions, means lower temps/pressures used. Can save energy cost as there is reduced energy demands for providing high temps and less electrical pumping cost for producing pressure. Means fewer CO2 emissions from burning of fossils.
• enable different reactions to be used w/ better atom economies / reduced waste
• often enzymes generating specific products and operating effectively close to room temp/pressures

Question 6

The effect of temperature on a Maxwell Boltzmaan?

Answer 6

• at higher temperatures , K.E of the molecules is increased.
• the Boltzmann flatterns and shifts to RIGHT
• shaded area under curve is greater
• higher proportion of molecules have sufficient energy to undergo a successful reaction when they collide
• R.O.R increases

Question 7

Homogenous catalysis?

Answer 7

• a reaction in which the catalyst/reactants are in the same physical state

Question 8

The oxygen ozone cycle?

Answer 8

• ozone created in stratosphere by combining O with O2 - process activated by sunlight
• O2 molecules absorb UV radiation and break down into O2. These atoms react with O2 molecules to form ozone. Exothermic : O2 –>2O. O2 + O –> O3
• reversible reaction as O3 molecules absorb UV radiation and converted back into O2 molecules and O atoms. O atoms react w/ O2 molecules to produce O3 again. Chemical released when atoms combine is converted into heat, overall effect is convert penetrating Uv into heat without loss of ozone
• ozone layer shields earth from harmful effects of UV radiation. A decrease in conc of ozone in ozone layer could lead to harmful effects