C3b

Question 1

What experiments can you do to follow the rate of reactions?

Answer 1

• a rate of reaction that produces gas can be observed by measuring how quickly gas is produced:
• measure the change in mass while the experiment is happening, mass will fall as gas is released, take readings of mass at regular time intervals
• measure volume of gas given off in a gas syringe at regular time intervals

Question 2

What does rates of reactions depend on?

Answer 2

• collision frequency of reacting particles (more collisions, faster reaction)
• energy transferred during collisions (particles have to collide with enough energy for a collision to be successful)

Question 3

How the amount of product determined?

Answer 3

-depends on the amount of reactant started with
-more reactant means more particles, which will have more reactions so more product
-total amount of product is directly proportional to limiting reactant
once all the limiting reactant is used up the reaction can’t continue, even if some reactants are in excess

Question 4

How is the rate of reaction increased?

Answer 4

-by more collisions

Question 5

What does the rate of reaction depend on?

Answer 5

• temperature
• concentration
• size of particles
• prensence of catalyst

Question 6

How does concentration (pressure) affects the rate of reaction?

Answer 6

• more concentrated solutions have more particles of a reactant in the same volume)
• making collisions more likely
• increasing pressure in a gas means molecules are more crowded , so frequency of collision increases

Question 7

How does temperature affects the rate of reaction?

Answer 7

• temperature increase means particles move faster, moving quicker means more collisions
• temperature increase, increases the energy in collisions (since particles move faster) meaning more particles will collide with enough energy to make reactions happen

Question 8

How does a catalyst affects the rate of reaction?

Answer 8

• increases number of successful collisions
• gives reacting particles a surface to stick to where they can collide with each other (reducing the energy needed to react before)
• number of collisions isn’t increased, but successful collisions are

Question 9

How does the size of particles affects the rate of reaction?

Answer 9

• breaking a solid reactant into smaller solid particles increases surface area
• particles around it have more area to work on, so collision frequency increases

Question 10

What are limiting reactants?

Answer 10

-the reactant being totally used up

Question 11

What are reactants in excess?

Answer 11

-reactants left behind at the end of a reaction

Question 12

Why do factories making fine powders have to be careful?

Answer 12

• fine powders of combustible materials disperse in air and burn incredibly fast because of the big surface area
• if there’s a spark they explode (very fast reaction that releases lots of gaseous produces very quickly)