the rate and extent of chemical change (2)

Question 1

what is collision theory

Answer 1

particles successfully collide with activation energy to react. The more collisions per second = faster rate of reaction

Question 2

Factors affecting the rate of reaction-:
temperature-
concentration-
pressure-
surface area-
catalyst-

Answer 2

temperature- particles have more kinetic energy so they successfully collide more frequently

concentration- there are more particles to collide with each other

pressure- gas particles in a smaller container collide more frequently

surface area- breaking a solid particle into smaller pieces makes more surfaces to collide with

catalyst- speeds up the reaction without being used up by providing an alternative, lower activation energy pathway

Question 3

Measuring rates of reaction: (equation)
precipitation and colour change-
change in mass-
the volume of gas given off-

Answer 3

rate of reaction = amount of reactant used or product formed/time

precipitation and colour change- you can record the speed at which a visual change occurs in the substance

change in mass- if a substance releases gas a product, you can measure the rate of mass change (faster mass change = after rate of reaction)

volume of gas given off- you can use a gas syringe to measure the volume of gas given off. The more gas produced in a time interval =a faster rate of reaction

Question 4

Sodium thiosulphate and HCl reaction (rate of reaction RP)

Answer 4

1. Measure a fixed volume of sodium thiosulphate into a conical flask.
2. Place the flask on a piece of paper with a black cross.
3. Add a fixed volume of hydrochloric acid and start a stopwatch immediately.
4. Observe the cross disappearing due to the formation of sulphur.
5. Stop the timer when the cross is no longer visible.
6. Repeat with different concentrations of sodium thiosulphate (dilute with water).

Question 5

Reversible reactions-

Answer 5

reversible reactions are where the products of a reaction can react to produce the reactants

eventually, they reach equilibrium which is where the rate of forward and reverse reactions are equal (only in a closed system)

Question 6

How can the position of equilibrium be shifted:

what does the position of equilibrium tell you

Answer 6

temperature-
pressure-
concentration-

more to the left = more reactants
more to the right = more product

one direction is exothermic and the other is endothermic

Question 7

thermal decomposition of hydrated copper sulphate

which way is endothermic

Answer 7

hydrated copper sulphate -> anhydrous copper sulphate + water

forward reaction is endothermic and reverse reaction is exothermic

Question 8

What is le chatelier’s principle

Answer 8

That a system will try and counteract changes made to conditions

eg. raising the temperature of the reaction will shift the equilibrium to the endothermic direction to try and decrease it

Question 9

raising temperature-
decreasing temperature-
increasing pressure-
decreasing pressure-
increasing concentration of reactants-
increasing concentration of product-

Answer 9

raising temperature- raising the temperature of the reaction will shift the equilibrium to the endothermic direction to try and decrease it

decreasing temperature- lowering the temperature of the reaction will shift the equilibrium to the exothermic direction to try and increase it
increasing pressure- increasing pressure makes equilibrium shift to the direction that produces fewer molecules of gas
decreasing pressure- decreasing pressure makes equilibrium shift to the direction that produces more molecules of gas
increasing concentration of reactants- more products made
increasing concentration of product - more reactants made