c8 rates of reaction

Question 1

mean rate of reaction
(reactant)

Answer 1

quantity of reactant used/time taken

Question 2

mean rate of reaction (product)

Answer 2

quantity of product formed/time taken

Question 3

unit of rate of reaction

Answer 3

g/s or cm3/s

Question 4

when plotting a graph for rate of reaction what goes in the x-axis?

Answer 4

time

Question 5

when do you draw a tangent on a specific point and calculate the gradient of the tangent?

Answer 5

to measure the rate of reaction at a specific time

Question 6

factors which affect the rates of chemical reactions include:

Answer 6

-the concentration of reactants in the solution
-the pressure of reacting gasses
-the surface area of solid reactants
-the temperature
-presence of a catalyst

Question 7

as you increase the temperature

Answer 7

the rate of reaction increases but same amount of products produced at the end

Question 8

what is concentration?
-increasing concentration increases rate

Answer 8

the number of particles dissolved in a given volume of solvent

Question 9

what is pressure
increased pressure=increased number of particles

Answer 9

a measurement of the number of particles in a given volume of gas

Question 10

is the surface area of a block or powder of that block greater?

Answer 10

powder surface area greater

Question 11

highest rate of reaction means

Answer 11

steepest gradient

Question 12

what does collision explain?

Answer 12

how various factors affect the rates of reactions

Question 13

chemical reactions can only occur when

Answer 13

reacting particles collide with each other and with sufficient energy

Question 14

what is the activation energy?

Answer 14

the minimum amount of energy that particles must have to react is called the activation energy

Question 15

what does increasing the concentration of reactants in solution, the pressure of reacting gases and the surface area of solid reactants increase?

Answer 15

the frequency of collisions so increases the rate of reaction

Question 16

increasing the temperature increases the frequence of collisions. What does this do?

Answer 16

this makes the collisions more energetic,and so increases the rate of reaction

Question 17

increasing temperature

Answer 17

particles have more kinetic energy
move faster
more collisions per second
collide with more energy

Question 18

larger surface area (lump cut up into smaller parts)

Answer 18

more particles exposed to other reactants more frequent collisions

Question 19

catalysts

Answer 19

reduce the amount of energy needed for particles to have a successful collision

Question 20

enzymes act as catalysts in?

Answer 20

biological systems

Question 21

what are reversible reactions?
example: A + B ⇌C + D

Answer 21

reactions where the products of the reaction can react to produce the original reactions

Question 22

the direction of reversible reactions can be changed by?

Answer 22

changing the conditions
For example: heat
ammonium chloride ⇌ ammonia + hydrogen chloride cool

Question 23

if a reversible reaction is exothermic in one direction, what is it in the opposite direction?

Answer 23

endothermic

Question 24

in reversible reactions, one reaction is exothermic and the other is endothermic so the same amount of energy is transferred in each case.
give an example

Answer 24

endothermic
ammonium chloride ⇌ ammonia + hydrogen chloride exothermic

Question 25

when a reversible reaction occurs in apparatus which prevents the escape of reactants and products, when is equilibrium reached?

Answer 25

when the forward and reverse reactions occur exactly at the same rate

Question 26

dynamic equilibrium

Answer 26

in a reversible reaction,rate of the forward reaction is equal o the rate of the backward reaction ina closed system

Question 27

three conditions affect the rate of reaction:

Answer 27

-temperature
-pressure
-concentration

Question 28

what is le chatlier’s principle?

Answer 28

When a reaction has reached dynamic equilibrium and a change occurs the position of equilibrium will move to counteract the change. This concept is known as Le Chatelier’s principle.

Question 29

required practical:the disappearing cross reaction
sodium thiosulfate solution + hcl–>sulfur (solid). what does sulfur do to the solution?

Answer 29

sulfur makes the solution go cloudy (turbidity)

Question 30

steps for disappearing cross reaction:

Answer 30

-use a measuring cylinder put 10cm3 of sodium thiosulfate in conical flask
-place the conical flask onto a printed black cross
-add 10cm3 of hydrochloric acid into the conical flask
-swirl solution , start a stopwatch

Question 31

after some time, what happens to the solution?

Answer 31

it turns cloudy, stop clock when cross no longer visible

Question 32

repeat again using?

Answer 32

lower concentrations of sodium thiosulfate

Question 33

repeat the whole experiment and ?

Answer 33

calculate the mean with no anomalies included

Question 34

reproducibility

Answer 34

can be repeated with different people or equipment but still same result

Question 35

what is the problem with this experiment?

Answer 35

different eyesights , people might see cross for longer however same size printed cross helps solve this