RATES OF CHEMICAL REACTIONS

Question 1

rate of a chemical reaction

Answer 1

the change in concentration of a reactant or product per time

Question 2

collision theory or reaction rates

Answer 2

a reaction occurs by collision of particles
only those in which particles collide with collision frequency greater than or = to activation energy are effective as not all collision result in a reaction

Question 3

rate of reaction is determine by:

Answer 3

measuring how quickly the reactant are used up
measuring how quickly the products are formed

Question 4

practical methods

Answer 4

1. measuring the volume
2. following change in mass
3. following process of a precipitation reaction

Question 5

1. measuring volume

Answer 5

• suitable for reaction involving production of a gas
• if gas is given off it pushes the plunger of gas syringe moves backwards
• vol. of gas is recorded at intervals of time
• graph of vol. against time is plotted

Question 6

2. following change in mass

Answer 6

• suitable for reaction involving production of gas
• as reaction proceeds mass of reaction mixture decreases
• mass of reacting mixture is recorded at intervals of time
• mass against time graph plotted

Question 7

3. following the progress of a precipitation reaction

Answer 7

• if a prec. is one of the products in reaction sol. goes cloudy
• reaction followed by placing paper with letter x underneath flask containing one of the reactants
• reaction is then started by adding the other reactant & recording the time taken for letter x to become invisible

Question 8

how do these graphs look

Answer 8

reaction is fast in the beginning, gradually slows down then finally stops
this is because the concentration of the reactant decreases with time until on or more of the reactants gets used up

Question 9

how would increasing concentration increase rate of reaction?

Answer 9

an increase in concentration leads to an increase in the number of particles reacting with e.g. HCl and this increases collision frequency because there is an increase if kinetic energy of particles as they’re colliding so rate of reaction increases

Question 10

how would increasing temperature increase rate of reaction?

Answer 10

an increase in temp. increases the kinetic energy of particles which increases collision frequency. this also increases the number of particles with kinetic energy greater than activation energy hence more successful collisions

Question 11

how would increasing surface area increase the reaction rate?

Answer 11

rate of reaction increases with increase of surface area because there is an increase in the number of particles exposed & how often the particles of e.g. acid react on the surface of e.g. marble and the greater the surface area of the reactant the more particles there are available to react hence more successful collisions