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chemistry > C5 > Flashcards

C5 Flashcards

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1
Q

what is the rate of reaction equation?

A

rate of reaction= amount of product formed / time

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2
Q

what are the three different ways that rate of reaction can be measured?

A

-precipitation
-change in mass
-volume of gas given off

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3
Q

how do you measure the rate of reaction using precipitation?

A

-draw a mark on a piece of paper, for example a cross.
-place a flask with a mixture of two reactant solutions over the mark
-observe the mark through the flask and time how long it takes for the mark to disappear

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4
Q

why is measuring the rate of reaction biast?

A

it is subjective, different people might disagree on when the mark disappears.

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5
Q

how do you measure the rate of reaction using change in mass?

A

-measure the rate of reaction using a mass balance
-as gas is released, the reading on the balance changes.
-the faster the reading on the balance drops, the faster the rate of reaction

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6
Q

what precautions do you have to take for a change in mass experiment?

A

-take safety precautions, do the experiment in a fume cupboard

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7
Q

what does cotton wool do in a change in mass experiment?

A

the cotton wool lets gases through but stops any solid, liquid or aqueous flying our during the reaction

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8
Q

how do you perform the volume of gas given off experiment?

A

-use a gas syringe to measure the volume of gas given off
-the more gas given off during a set time, the faster the reaction

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9
Q

what graph can you plot for the change in mass experiment?

A

change in mass against time

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10
Q

what graph can you plot for the volume of gas given off experiment?

A

gas volume against time elapsed

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11
Q

why do you have to make sure the gas syringe is the right size for the volume of gas given off experiment?

A

if the reaction is too vigorous, you could blow the plunger out of the end of the syringe.

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12
Q

what can you use the hydrochloric acid and marble chips experiment for?

A

to show how surface area affects the rate of reaction

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13
Q

how do you set up the hydrochloric acid and marble chip experiment

A

-gas syringe connected to a flask
-marble chips
dilute HCL
-CO2 gas

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14
Q

how do you perform the hydrochloric acid and marble chips experiment?

A

-measure the volume of gas produced use gas syringe.
-take readings at regular time intervals and record results in a table
-

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15
Q

how do you perform the hydrochloric acid and marble chips experiment?

A

-measure the volume of gas produced use gas syringe.
-take readings at regular time intervals and record results in a table
-repeat the experiment with exactly the same volume and concentration of acid and exactly the same mass of marble chips but with the marble more crunched up
-then repeat the same with same mass of powdered chalk

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16
Q

which way do the volume and time labels go on a graph?

A

volume y axis- up
time x axis- across

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17
Q

what is the reaction of magnesium metal with dilute HCL good for?

A

measuring the effects of changing concentration on reaction rate

the reaction gives off hydrogen gas, so you can measure loss of mass using a mass balance

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18
Q

how do you work out the gradient?

A

change in y over change in x

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19
Q

how is rate inversely proportional?

A

the longer something takes, the slower the rate

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20
Q

what four things does the rate of a reaction depend on?

A

-concentration
-temperature
-pressure (for gases)
-size of particles

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21
Q

how is rate of reaction affected by collision frequency?

A

the more successful collision there are, the faster the reaction.

energy is transferred during a collision, particles have to collide with enough energy for the collision to be successful

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22
Q

what is a successful collision?

A

a collision that ends in the particles reacting to form products

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23
Q

how does increasing temperature increase the rate of reaction?

A

when the temperature is increased, the particles move faster with more energy and collide more often, this means there will be more successful collisions which will increase the rate of reaction.

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24
Q

how does increasing concentration increase the rate of reaction?

A

there are more particles in a given volume, which means the particles are more likely to collide and cause successful collisions, increasing the rate of reaction

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25
Q

how does larger surface area/size of the particles increase rate of reaction?

A

if a reactant is a solid and it is broken into smaller pieces, it has a larger surface area to volume ratio.

the particles around it have more area to work on so the amount of collision increases which means successful collisions increases

26
Q

why are catalysts important?

A

they increase the rate of reaction and reduce energy costs

27
Q

what is a catalyst?

A

a substance which increases the rate of a reaction without being chemically changed or used up

28
Q

how do catalysts work?

A

decrease the activation energy by providing an alternative pathway that has a lower activation energy

29
Q

how can you identify a catalyst in a chemical reaction?

A

-if you have a solid that you think might be a catalyst in a reaction you can:

-measure the reaction rate without the solid present, and then again with a mass of the unknown solid.
-if the rate increases, and the solid appears unchanged it is a catalyst

30
Q

how do you keep a fair experiment when comparing?

A

keep the volumes and concentrations of the solutions equal and also the temperature

31
Q

what is a reversible reaction?

A

a reaction where the products can react with each other to produce the original reactants ( it can go both ways)

32
Q

what three things can change the position of equlibrium?

A

temperature
pressure ( only in gases)
concentration

33
Q

what is le chateliers principle?

A

if there is any change in concentration, pressure or temperature in a reversible reaction, the equlibrium position will change to counteract that change.

34
Q

how does temperature change the position of equlibrium?

A

if you decrease the temp it will move in the exothermic direction to produce more heat

if you increase temp the equilibrium will move in the endothermic direction to absorb heat.

35
Q

how does pressure change the position of equlibrium?

A

if you increase the pressure, the equlibrium will move towards the side that has less moles to reduce pressure

if you decrease the pressure, the equlibrium will move towards the side with more moles to increase pressure

36
Q

how does concentration affect the change of position of equlibrium?

A

if you increase the concentration of the reactants, the equlibrium will move to the right to use up the reactants

if you increase the concentration of the products, the equlibrium will move to the left to use up the products

37
Q

what is a contact process?

A

a process used to make sulfuric acid from sulfur, water and air

38
Q

how do you perform the contact process?

A
  1. burn the sulfur
    sulfur + oxygen = sulfur dioxide
  2. react sulfur dioxide with oxygen using vandium catalyst at 450 degrees.
    sulfur dioxide + oxygen = sulfur trioxide
  3. react sulfur trioxide with water to form sulfur acid
39
Q

what are the three conditions for the haber process?

A
  1. iron catalyst
  2. high temperature (450 degrees)
  3. high pressure (200atm)
40
Q

what is the word symbol for the haber process?

A

nitrogen + hydrogen ⇌ ammonia

41
Q

what is the symbol equation for the haber process?

A

N2 + 3H2 ⇌ 2NH3

42
Q

where do the reactants from the haber process come from?

A

-nitrogen - fractionally distillating the air- the air is made up of 78% of nitrogen
hydrogen- hydrocarbons being made

43
Q

why is the haber process so important?

A

the ammonia made in the haber process is used to make nitrogen fertilisers which we used to grow food to eat

44
Q

what two manufacturing process’ use catalysts?

A

-haber process
-contact process

45
Q

ignore

A

ignore

46
Q

true or false there is still an ongoing reaction during equilibrium?

A

true- but there’s no overall effect. it’s dynamic equlibrium

47
Q

what does dynamic equlibrium mean?

A

the concentration of the reactants and products have reached a balance and won’t change

48
Q

what must happen for equlibrium to be reached?

A

that the reversible reaction occurs in a closed system. non of the products or reactants can escape

49
Q

what does it mean when the equlibrium lies to the right?

A

lots of products not much reactants

50
Q

what does it mean when equlibrium lies to the left

A

lots of reactants but not much products

51
Q

does an endothermic reaction require energy or release energy?

A

requires energy

52
Q

what is the equation for calculating the concentration of a solution?

A

mass of solute in g / volume of solution in dm3

53
Q

why are fertilisers so important in agriculture?

A

-increase crop yields
-they improve the quality of crops

54
Q

what are two disadvantages of doing the haber process with lower pressure?

A

-rate of reaction will be slower as there will be less frequent collisions per second

55
Q

what is meant by pressure in terms of chemistry?

A

the same meaning as concentration- there are more particles in a given volume.

56
Q

what is concentration a measure of?

A

the amount of substance that is dissolved in a certain volume of solution

57
Q

what is concentration measured in?

A

g/dm cubed

58
Q

what is the concentration equation?

A

conc= mass of solute / volume of solution

59
Q

explain the haber process:

A
  1. take hydrogen + nitrogen and put them into a reaction vessel (this is where the temperature is 450 degrees and the pressure is 200 atm
  2. in here the nitrogen and hydrogen will react to make ammonia
  3. ammonia has a low boiling point- so it will fit through a tube into a condenser where it will condense into a liquid to be used as a fertiliser- but gaseous nitrogen + hydrogen have high boiling points so they will not condense and can be recyled
60
Q

why is 450 degrees used?

A

it acts as a compromise- whilst a low temp gives us a higher yield because it favours the forward reaction, a higher temperature is needed for the particles to collide and allow a reaction to take place.

450 degrees gives us a higher rate of reaction.

61
Q

why do we use a high pressure in the haber process?

A

-a higher pressure means the particles will collide more frequently- greater rate of reaction

  • a higher pressure also means the equlibrium will shift to the right were there are less product molecules than reactant molecules.

chemistry (3 decks)

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