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Chemistry (Fin) > Paper 2 C6 - The Rate and Extent of Chemical Change > Flashcards

Paper 2 C6 - The Rate and Extent of Chemical Change Flashcards

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1
Q

Give the two equations used to calculate rate of reaction

A

reactants used/time
products formed/time

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2
Q

Give the two possible units for rate of reaction

A

cm³/s
mol/s

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3
Q

Give one observation that can be made on a graph when a reaction finishes

A

The graph levels off

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4
Q

Describe how to calculate the rate of reaction at a specific point on a graph

A
  1. Draw a tangent to the curve
  2. Calculate the gradient of the tangent
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5
Q

The steeper the tangent of a rate of reacton graph, the _________ the reaction

A

faster

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6
Q

Identify five factors that affect the rate of chemical reactions

A
  • Concentration
  • Pressure
  • Surface area
  • Temperature
  • Catalysts
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7
Q

Define collision theory

A

Theory that a chemical reaction only happens if particles collide with enough energy

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8
Q

Define activation energy

A

Minimum amount of energy particles need to react

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9
Q

Explain why an increase in temperature increases rate of reaction

A

Increases kinetic energy of particles
–> More frequent, energetic collisions
—> Faster rate of reaction

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10
Q

Explain why an increase in surface area increases rate of reaction

A

More area for reactant particles to collide with
–> More frequent successful collisions
—> Faster rate of reaction

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11
Q

Explain why an increase in concentration of a solution increases rate of reaction

A

Particles are closer together
–> More frequent successful collisions
—> Faster rate of reaction

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12
Q

Explain why an increase in pressure increases rate of reaction

A

Particles are closer together
–> More frequent successful collisions
—> Faster rate of reaction

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13
Q

Define catalyst

A

Substance that speeds up a chemical reaction without being used up

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14
Q

Explain how catalysts increase the rate of a reaction

A

Provide alternative pathway with lower activation energy
–> More particles have enough energy to react
—> More frequent successful collisions

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15
Q

True/False: Catalysts increase the overall energy change of a reaction

A

False - it stays the same

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16
Q

Plan an experiment to investigate how the concentration of a reactant affects the rate of reaction (disappearing cross experiment)

A
  1. Use a measuring cylinder to put 10 cm³ of sodium thiosulfate into a conical flask
  2. Place the conical flask onto a printed black cross
  3. Add 10cm³ of hydrochloric acid to the conical flask
  4. Swirl solution and start a stopwatch
  5. Look down through the top of the flask
  6. Stop the clock when the cross can no longer be seen
  7. Repeat experiment using different concentrations of sodium thiosulfate
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17
Q

Give two control variables in the disappearing cross experiment

A
  • Volume of sodium thiosulfate
  • Volume and concentration of hydrochloric acid
18
Q

Give one independent variable in the disappearing cross experiment

A

Concentration of sodium thiosulfate

19
Q

Give one dependent variable in the disappearing cross experiment

A

Time taken for cross to disappear

20
Q

Suggest one problem with the diappearing cross experiment

A

People have different eyesights, so may not get the same results

21
Q

Plan an experiment to investigate how the concentration of a reactant affects the rate of reaction (volume of gas released)

A
  1. Use a measuring cylinder to put 50cm³ of hydrochloric acid into a conical flask
  2. Connect the bung and delivery tube to the flask
  3. Connect the tube to the gas syringe/upside down measuring cylinder
  4. Add a 3cm piece of magnesium ribbon to the flask
  5. Start a stopwatch
  6. Record the volume of hydrogen gas collected every 10 seconds
  7. Continue until no more hydrogen is given off
  8. Repeat experiment with different concentrations of hydrochloric acid
22
Q

Give one independent variable in the rate of reaction (volume of hydrogen released) experiment

A

Concentration of hydrochloric acid

23
Q

Give one dependent variable in the rate of reaction (volume of hydrogen released) experiment

A

Time taken for hydrogen to stop being produced

24
Q

Give one control variable in the rate of reaction (volume of hydrogen released) experiment

A

Length/mass of magnesium ribbon

25
Q

Name the type of reaction that includes the products reacting to form the original reactants

A

Reversible reaction

26
Q

Write the symbol used to represent a reversible reaction

A

⇌

27
Q

Give an example of a reversible reaction

A

The Haber process
nitrogen + hydrogen ⇌ ammonia
N₂ + 3H₂ ⇌ 2NH₃

28
Q

If a reversible reaction is endothermic in one direction, it will be ___________ in the ______ direction

A

exothermic, other

29
Q

In a reversible reaction, the same amount of ______ is transferred each way

A

energy

30
Q

Give a synonym for a closed system

A

A sealed container

31
Q

Define equilibrium

A

When the rate of a forward reaction is equal to the rate of a backward reaction

32
Q

Name the system that equilibrium can take place in

A

Closed system

33
Q

State why equilibrium can be reached in a closed system

A

Products/reactants cannot escape

34
Q

Name the principle that predicts how an equilibrium responds to changes in different conditions

A

Le Chatelier’s Principle

35
Q

State why equilibriums respond to changes in conditions

A

To keep the amount of reactant relative to the amount of product stable

36
Q

Describe how increased concentration of reactants affect the position of equilibrium

A

Forward reaction is favoured
–> Equilibrium shifts towards products
—> More product is made

37
Q

Describe how increased concentration of products affect the position of equilibrium

A

Backward reaction is favoured
–> Equilibrium shifts towards reactants
—> More reactant is made

38
Q

Describe how increased temperature affects the position of equilibrium

A

Equilibrium shifts in direction of endothermic reaction
–> (decreases temperature back to normal)

39
Q

Describe how decreased temperature affects the position of equilibrium

A

Equilibrium shifts in direction of exothermic reaction
–> (increases temperature back to normal)

40
Q

Describe how increased pressure affects the position of equilibrium

A

Equilibrium shifts to side with fewer molecules
–> (increased rate of reaction creates more)

41
Q

Describe how decreased pressure affects the position of equilibrium

A

Equilibrium shifts to side with more molecules
–> (decreased rate of reaction creates less)

42
Q

True/False: Changing the pressure has no effect on a reversible reaction unless one of the products or reactants is a gas.

A

True

Chemistry (Fin) (7 decks)

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