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chemistry > rates (p2) > Flashcards

rates (p2) Flashcards

1
Q

What is rate of reaction?

A

A measure of how quickly reactants turn into product

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2
Q

What equations are used to calculate the mean rate of reaction?

A

quantity of reactant used รท time
or
quantity of product formed รท time

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3
Q

What are the units of rate of reaction?

A

g/s
or
cmยณ/s

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4
Q

What are the usual units for mass (in chemistry)?

A

g

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5
Q

What are the units for volume

A

cmยณ

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6
Q

A steep gradient on a rate of reaction graph shows what?

A

fast reaction

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7
Q

What does it mean when a graph showing rate of reaction levels off?

A

the reaction is complete and no more product is produced

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8
Q

[๐—›๐—ถ๐—ด๐—ต๐—ฒ๐—ฟ ๐˜๐—ถ๐—ฒ๐—ฟ] How can the actual rate of reaction be determined from a rate of reaction graph?

A

draw a tangent to the curve, measure the gradient of the tangent

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9
Q

[๐—›๐—ถ๐—ด๐—ต๐—ฒ๐—ฟ ๐˜๐—ถ๐—ฒ๐—ฟ] What is the equation for measuring the gradient?

A

change in y รท change in x

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10
Q

What is pressure?

A

A measure of how close together gas particles are

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11
Q

What is concentration?

A

The number of particles in a given volume

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12
Q

What is surface area?

A

The area of a solid that is exposed to the surface

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13
Q

How could you increase the surface area of a solid reactant?

A

Break it into smaller pieces

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14
Q

Which has a larger surface area: 10 g of magnesium ribbon or 10 g of magnsium powder?

A

magnesium powder

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15
Q

What happens to the rate of a reaction when the concentration of reactants in solution is increased?

A

rate increases

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16
Q

What happens to the rate of a reaction when the temperature is increased?

A

rate increases

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16
Q

What happens to the rate of a reaction when the pressure of reacting gases is increased?

A

rate increases

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17
Q

What happens to the rate of a reacton when a solid reactant is broken into smaller pieces?

A

rate increases

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17
Q

What methods can you use to collect a gas?

A

Collect in gas syringe
or
collect in inverted measuring cylinder under water

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17
Q

What happens to the rate of a reaction when the surface area of solid reactants increases?

A

rate increases

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18
Q

What piece of apparatus should be used to measure 20 cmยณ of acid?

A

Measuring cylinder

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19
Q

When will solutions turn cloudy?

A

When an insoluble solid is produced

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20
Q

What are the independent and dependent variables in the investigation: ๐‘จ ๐’”๐’•๐’–๐’…๐’†๐’๐’• ๐’Ž๐’†๐’‚๐’”๐’–๐’“๐’†๐’” ๐’•๐’‰๐’† ๐’•๐’Š๐’Ž๐’† ๐’•๐’‚๐’Œ๐’†๐’ ๐’‡๐’๐’“ ๐’‚ ๐’„๐’“๐’๐’”๐’” ๐’•๐’ ๐’…๐’Š๐’”๐’‚๐’‘๐’‘๐’†๐’‚๐’“ ๐’˜๐’‰๐’†๐’ ๐’…๐’Š๐’‡๐’‡๐’†๐’“๐’†๐’๐’• ๐’„๐’๐’๐’„๐’†๐’๐’•๐’“๐’‚๐’•๐’Š๐’๐’๐’” ๐’๐’‡ ๐’”๐’๐’…๐’Š๐’–๐’Ž ๐’•๐’‰๐’Š๐’๐’”๐’–๐’๐’‡๐’‚๐’•๐’† ๐’‚๐’“๐’† ๐’–๐’”๐’†๐’…?

A

Independent: concentration of sodium thiosulfate
Dependent: time taken for cross to disappear

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20
Q

Why can measuring the time taken for a solution to turn cloudy indicate the rate of reaction?

A

the solution turns cloudy when the product is formed. Measuring the time allows us to do ๐™ฆ๐™ช๐™–๐™ฃ๐™ฉ๐™ž๐™ฉ๐™ฎ ๐™ค๐™› ๐™ฅ๐™ง๐™ค๐™™๐™ช๐™˜๐™ฉ ๐™›๐™ค๐™ง๐™ข๐™š๐™™ รท ๐™ฉ๐™ž๐™ข๐™š

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21
Q

What are the independent and dependent variables in the investigation: ๐‘จ ๐’”๐’•๐’–๐’…๐’†๐’๐’• ๐’Ž๐’†๐’‚๐’”๐’–๐’“๐’†๐’” ๐’•๐’‰๐’† ๐’—๐’๐’๐’–๐’Ž๐’† ๐’๐’‡ ๐’ˆ๐’‚๐’” ๐’‘๐’“๐’๐’…๐’–๐’„๐’†๐’… ๐’˜๐’‰๐’†๐’ ๐’…๐’Š๐’‡๐’‡๐’†๐’“๐’†๐’๐’• ๐’„๐’๐’๐’„๐’†๐’๐’•๐’“๐’‚๐’•๐’Š๐’๐’๐’” ๐’๐’‡ ๐’‰๐’š๐’…๐’“๐’๐’„๐’‰๐’๐’๐’“๐’Š๐’„ ๐’‚๐’„๐’Š๐’… ๐’‚๐’“๐’† ๐’–๐’”๐’†๐’…?

A

Independent: concentration of hydrochloric acid
Dependent: volume of gas produced

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21
Q

What variables should be controlled in the investigation: ๐‘จ ๐’”๐’•๐’–๐’…๐’†๐’๐’• ๐’Ž๐’†๐’‚๐’”๐’–๐’“๐’†๐’” ๐’•๐’‰๐’† ๐’•๐’Š๐’Ž๐’† ๐’•๐’‚๐’Œ๐’†๐’ ๐’‡๐’๐’“ ๐’‚ ๐’„๐’“๐’๐’”๐’” ๐’•๐’ ๐’…๐’Š๐’”๐’‚๐’‘๐’‘๐’†๐’‚๐’“ ๐’˜๐’‰๐’†๐’ ๐’…๐’Š๐’‡๐’‡๐’†๐’“๐’†๐’๐’• ๐’„๐’๐’๐’„๐’†๐’๐’•๐’“๐’‚๐’•๐’Š๐’๐’๐’” ๐’๐’‡ ๐’”๐’๐’…๐’Š๐’–๐’Ž ๐’•๐’‰๐’Š๐’๐’”๐’–๐’๐’‡๐’‚๐’•๐’† ๐’‚๐’“๐’† ๐’–๐’”๐’†๐’…?

A
  • volume of sodium thiosulfate
  • concentration of hydrochloric acid
  • volume of hydrochloric acid
  • same cross
  • temperature
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22
Q

What is collision theory?

A

the theory that for chemical reactions to occur reacting particles must collide with sufficient energy

23
Q

What is the activation energy?

A

the minimum amount of energy that reacting particles must collide with for a reaction to occur

24
Q

What happens if reacting particles collide with energy less than the activation energy?

A

no reaction - they stay as reactants

25
Q

What happens if reacting particles collide with energy greater than or equal to the activation energy?

A

they are converted into products

26
Q

What does the term ๐’‡๐’“๐’†๐’’๐’–๐’†๐’๐’„๐’š ๐’๐’‡ ๐’„๐’๐’๐’๐’Š๐’”๐’Š๐’๐’๐’” mean?

A

the number of collisions in a given amount of time (e.g. collisions per second)

27
Q

How can you increase the rate of a reaction?

A
  1. increase the frequency of collisions
  2. increase the energy of collisions
28
Q

Why does increasing the surface area increase the rate of a reaction?

A
  1. increases the number of particles available for collisions
  2. which increases the frequency of collisions
  3. which increases the chances of successful collisions with energy higher than the activation energy
29
Q

Why does increasing the concentration of reactants increase the rate of a reaction?

A
  1. Increases the number of particles in a given volume
  2. Increases the frequency of collisions
  3. Increases the chances of successful collisions with energy higher than the activation energy
30
Q

Why does increasing the pressure of reacting gases increase the rate of a reaction?

A
  1. Causes particles to be closer together
  2. Increases the frequency of collisions
  3. Increases the chances of successful collisions with energy higher than the activation energy
31
Q

Why does increasing the temperature increase the rate of a reaction?

A
  1. Increases the kinetic energy of the particles
  2. Increases the frequency and energy of collisions
  3. Increases the chances of successful collisions with energy higher than the activation energy
32
Q

What happens to the rate of the reaction if the frequency of collisions doubles?

A

rate doubles

33
Q

What happens to the rate of a reaction if the frequnecy of collisions is halved?

A

rate halves

34
Q

What are catalysts?

A

Substances that increase the rate of chemical reactions without getting used up themselves

35
Q

Why are catalysts not included in chemical equations?

A

they are not used up or produced in chemical reactions

36
Q

Why does using a catalyst increase the rate of a reaction?

A
  1. Catalysts provide a different pathway for the reaction with a lower activation energy
  2. More collisions have energy higher than the activation energy
37
Q

What does a reaction profile for a catalysed reaction look like?

A

a profile with a lower energy reaction pathway for the reaction with a catalyst

38
Q

What does this symbol โ‡Œ mean?

A

a reversible reaction

39
Q

What is a reversible reaction?

A

A reaction in which reactants react to form products and the products can react to form the reactants

40
Q

How can the direction of a reversible reaction be changed?

A

by changing the conditions (e.g. heat for one direction, cool for the other direction)

41
Q

What is an exothermic reaction?

A

A reaction that transfers energy to the surroundings

42
Q

What is an endothermic reaction?

A

A reaction that takes in energy from the surroundings

43
Q

If a reversible reaction is exothermic in one direction, what type of reaction is the reverse reaction?

A

Endothermic

44
Q

What is dynamic equilibrium?

A

When the rate of the forward reaction is exactly the same as the rate of the reverse reaction

45
Q

What conditions are needed for dymanic equilibrium to be reached?

A

a closed system (which prevents the escape of reactants and products)

46
Q

What is a closed system?

A

Apparatus set up in a way that prevents anything (e.g. reactants and products) from entering or leaving

47
Q

[๐—›๐—ถ๐—ด๐—ต๐—ฒ๐—ฟ ๐˜๐—ถ๐—ฒ๐—ฟ] How does a system at equilibrium respond to changes?

A
  • The system will stop being at equilibrium
  • As the rate of either the forward or the reverse reaction will increase
  • Until a new equilibrium is reached
48
Q

[๐—›๐—ถ๐—ด๐—ต๐—ฒ๐—ฟ ๐˜๐—ถ๐—ฒ๐—ฟ] What is Le Chatelierโ€™s Principle?

A

If the conditions of a system at equilibrium change, the system will respond to counteract the change

49
Q

[๐—›๐—ถ๐—ด๐—ต๐—ฒ๐—ฟ ๐˜๐—ถ๐—ฒ๐—ฟ] If the temperature increases, how will a system at equilibrium respond?

A

System will decrease the temperature

50
Q

[๐—›๐—ถ๐—ด๐—ต๐—ฒ๐—ฟ ๐˜๐—ถ๐—ฒ๐—ฟ] If the temperature of a system at equilibrium decreases, how will the system respond?

A

System will increase the temperature

51
Q

[๐—›๐—ถ๐—ด๐—ต๐—ฒ๐—ฟ ๐˜๐—ถ๐—ฒ๐—ฟ] If the temperature of a system at equilibrium increases, will the exothermic or endothermic reaction be favoured?

A

Endothermic reaction

52
Q

[๐—›๐—ถ๐—ด๐—ต๐—ฒ๐—ฟ ๐˜๐—ถ๐—ฒ๐—ฟ] If the temperature of a system at equilibrium decreases, will the exothermic or endothermic reaction be favoured?

A

Exothermic reaction

53
Q

[๐—›๐—ถ๐—ด๐—ต๐—ฒ๐—ฟ ๐˜๐—ถ๐—ฒ๐—ฟ] If the concentration of a reactant is increased in a system at equilibrium, which reaction is favoured?

A

The forward reaction

54
Q

[๐—›๐—ถ๐—ด๐—ต๐—ฒ๐—ฟ ๐˜๐—ถ๐—ฒ๐—ฟ] If the concentration of a reactant is decreased in a system at equilibrium, which reaction is favoured?

A

The reverse reaction

55
Q

[๐—›๐—ถ๐—ด๐—ต๐—ฒ๐—ฟ ๐˜๐—ถ๐—ฒ๐—ฟ] If the concentration of a product is increased in a system at equilibrium, which reaction is favoured?

A

The reverse reaction

56
Q

[๐—›๐—ถ๐—ด๐—ต๐—ฒ๐—ฟ ๐˜๐—ถ๐—ฒ๐—ฟ] If the concentration of a product is decreased in a system at equilibrium, which reaction is favoured?

A

The forward reaction

57
Q

[๐—›๐—ถ๐—ด๐—ต๐—ฒ๐—ฟ ๐˜๐—ถ๐—ฒ๐—ฟ] If the rate of the forward reaction increases in a reversible system, what will happen to the concentration of reactants and products?

A
  • Concentration of reactants decrease
  • Concentration of products increase
58
Q

[๐—›๐—ถ๐—ด๐—ต๐—ฒ๐—ฟ ๐˜๐—ถ๐—ฒ๐—ฟ] If the pressure is increased in a system at equilibrium, which reaction is favoured?

A

the reaction which produces fewer molecules of gas

59
Q

[๐—›๐—ถ๐—ด๐—ต๐—ฒ๐—ฟ ๐˜๐—ถ๐—ฒ๐—ฟ] If the pressure is decreased in a system at equilibrium, which reaction is favoured?

A

the reaction which produces more molecules of gas

60
Q

[๐—›๐—ถ๐—ด๐—ต๐—ฒ๐—ฟ ๐˜๐—ถ๐—ฒ๐—ฟ] ๐—กโ‚‚๐—ขโ‚„ (๐—ด) โ‡Œ ๐Ÿฎ ๐—ก๐—ขโ‚‚ (๐—ด) Which reaction will be favoured if the pressure increases?

A

the reverse (backwards) reaction as there are fewer gaseous molecules on the left side

61
Q

[๐—›๐—ถ๐—ด๐—ต๐—ฒ๐—ฟ ๐˜๐—ถ๐—ฒ๐—ฟ] What does yield mean?

A

How much of a substance is produced

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