c8

Question 1

equation for mean rate of reaction

Answer 1

quantity of reactant used or product formed / time taken

Question 2

what is the unit for the rate of reaction?

Answer 2

g/s or cm^3/s

Question 3

how can the quantity of reactant or product be measured?

Answer 3

mass in grams or volume in cm^3

Question 4

what are the factors which affect the rate of reaction?

Answer 4

the concentration of reactants in solution
the pressure of the reacting gases
the surface area of solid reactants
the temperature
the presence of catalysts

Question 5

how does increasing pressure affect rate of reaction?

Answer 5

increasing pressure would mean there are more particles in a given volume, therefore there would be more collisions so the rate of reaction will increase

Question 6

how does increasing concentration affect the rate of reaction?

Answer 6

increasing concentration would mean there are more reactant particles moving together so there would be more collisions per unit time and so the reaction rate is increased

Question 7

how does increasing temperature affect the rate of reaction?

Answer 7

it increases the frequency of collisions and makes the collisions more energetic and so increases the rate of reaction.

Question 8

how does increased surface area affect rate of reaction?

Answer 8

the particles around it will have more area to work on at increased surface area, so there will be collisions more frequently

Question 9

what are catalysts?

Answer 9

a catalyst is a substance that speeds up a reaction without being used up in the reaction itself.

Question 10

how do catalysts affect the rate of reaction?

Answer 10

they reduce the activation energy needed for the reaction to occur by providing an alternative reaction pathway with a lower activation energy.
this would mean that the rate of reaction increases because less energy is required.

Question 11

what is collision theory?

Answer 11

it states that chemical reactions can occur only when reacting particles collide with each other and with sufficient energy.

Question 12

what is activation energy?

Answer 12

the minimum amount of energy that particles must have to react

Question 13

what are enzymes?

Answer 13

they act as catalysts in biological systems

Question 14

what are reversible reactions?

Answer 14

when the products of the reaction can react to produce the original reactant.
if a reaction is exothermic one way, then it is endothermic the other way.

Question 15

what is equilibrium?

Answer 15

in a closed system when the rate of forward reaction = rate of reverse reaction

Question 16

what happens when a change is made to the conditions of a system at equilibrium?

Answer 16

the system responds to counteract the change - le chatelier’s principle

Question 17

effect of changing concentration in an equilibium

Answer 17

if the concentration of the reactants increase, more products will be formed until equilibrium is reached
if the concentration of the products decrease, more reactants react until equilibrium is reached again.

Question 18

effect of when temperature increases of a system at equilibrium

Answer 18

equilibrium moves in the endothermic direction to reverse the change

Question 19

effect of when temperature decreases of a system at equilibrium

Answer 19

equilibrium moves to the exothermic direction to reverse the change

Question 20

effect of when pressure increases of a system at eqilibrium

Answer 20

equilibrium position shifts to side with smaller number of molecules to decrease the pressure again

Question 21

effect of when pressure decreases of a system at eqilibrium

Answer 21

equilibrium position shifts to side with larger number of molecules to increase the pressure again

Question 22

how can u measure the rate of reaction by measuring the change in mass - practical

Answer 22

set up a conical flask with the solution and cover it will cotton wool at the top of the flask - this is so that the gas can escape but the acid cannot. put this on a weighing scale and start the timer.
as the gas is released, the mass disappearing is measured on the balance. th quicker the reading drops, the faster the reaction.
it is accurate because the balance is quite accurate, however, it releases the gas straight into the room

Question 23

measuring rate of reaction by observing the colour change

Answer 23

add your solution into a conical flask uing a measuring cylinder and place over a black cross. add your acid and swirl. start a stopwatch. the solution should turn cloudy. stop the stopwatch when you can no longer see the black cross. repeat using different concentrations of the solution. repeat whole experiment to calculate a mean and draw a graph.

Question 24

what is reproducibility?

Answer 24

if a measurment can be repeated by someone else or using a different technique and you can get the same results

Question 25

measuring volume of gas to see the rate of reaction

Answer 25

use measuring cylinder and place a certain volume of the acid into a conical flask. attach it to a bung and delivery tube. place the delivery tube into a container filled with water. then place an upturned measuring cylinder also filled with water over the delivery tube. add the metal strip into the conical flask and start the stopwatch. the reaction will prouce a gas which will be trapped in the measuring cylinder and the volume can be measured.
repeat experiment with different concentrations.