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Chemistry > 4.1 Rates of Reactions > Flashcards

4.1 Rates of Reactions Flashcards

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1
Q

Activation Energy

A

The required energy that particles need to react, if particles don’t have this energy, they will just rebound and remain unchanged

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2
Q

Collision Frequency

A

How often do particles collide with each other?

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3
Q

Percentage success

A

What percentage of the collisions have enough energy?

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4
Q

Factors effecting rate of reaction

A
  • Surface Area
  • Temperature
  • Catalysts
  • Concentration/Pressure
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5
Q

Surface area, Rate

A
  • Increasing surface area increases rate of reaction
  • As more of the solid is exposed to particles
  • Meaning the collision frequency is higher
  • So there are more successful collisions per unit time
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6
Q

Concentration/Pressure, Rate

A
  • Higher solution concentration/gas pressure increases rate of reaction
  • As there are more particles per unit volume
  • Meaning collision frequency is higher
  • Meaning more successful collisions per unit time
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7
Q

Temperature, Rate

A
  • Increase temperature increases rate of reaction
  • As the particles have more kinetic energy
  • Meaning the percentage of collisions with enough energy is higher
  • Meaning more successful collisions per unit time
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8
Q

Catalysts, Rate

A
  • Presence of a catalyst increase rate of reaction
  • As they provide an alternate route with a lower activation energy
  • So the percentage of collisions with enough activation energy is higher
  • Meaning more successful collisions per unit time
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9
Q

How do you increase surface area?

A

Cut or grind up solid, smaller prices = higher surface area

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10
Q

Marble Chip Experiment

A
  • The effect of surface area on rate is usually measured by reacting calcium carbonate chips and hydrochloric acid
  • Higher surface area = more gas produced in 10s (not overall)
  • Gas Syringe
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11
Q

Equation for Marble Chip Experiment

A

CaCO3 (s) + 2HCl —> CaCl2(aq) + H2O(l) + CO2(g)

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12
Q

Marble Chip Experiment Variables

A

Input: Different sizes of chips
Output: Amount of gas produced
Controls: Temp, Mass of CaCO3, Volume and Conc of HCl

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13
Q

Marble Chip Experiment Graph

A
  • Higher Surface Area = Steeper line

- Same final volume as amount of reactants has not changed

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14
Q

Rate of Reaction Equation

A

Rate = Change in reactant or product/time taken

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15
Q

Disappearing across Experiment

A
  • The effect of concentration is usually demonstrated by reacting sodium thiosulphate solution with Hydrochloric Acid
  • Sulphur is slowly produced and you can’t see through mixture after a while
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16
Q

Equation for disappearing cross experiment

A

Na2S2O3 + 2HCl —> 2NaCl + S + SO2 + H2O

17
Q

Disappearing Cross Experiment Variables

A

Input: Concentration is Sodium Thiosulphate
Output: time taken for cross to disappear
Controls: Total volume, Concentration of HCl, Temp

rate = 1/time

18
Q

Disappearing Cross Experiment Results

A
  • Graph shows a straight line, meaning it’s directly proportional
  • Meaning double concentration, doubles rate of reaction
19
Q

Magnesium and Acid Experiment

A
  • This experiment is used to show the effect of temperature by reacting magnesium and hydrochloric acid
  • Heat HCl until magnesium dissapears
20
Q

Magnesium and Acid Experiment Equation

A

Mg + 2HCl —> MgCl2 + H2

21
Q

Magnesium and Acid Experiment Variables

A

Input: Temp of HCl
Output: Time taken for Mg to disappear
Controls: Mass & SA of magnesium, Volume and conc of HCl

22
Q

Magnesium and Acid Experiment Results

A
  • Not directly proportional, not a straight line

- Doesn’t go through origin because rate isn’t 0 and 0 degrees

23
Q

What are catalysts?

A
  • Increase Rate

- Remain Chemically Unchanged

24
Q

How do catalysts work?

A

-Provide an alternate route with lower activation energy

25
Q

Hydrogen Peroxide Experiment

A
  • Shows the effect of catalysts using the decomposition of hydrogen peroxide
  • The reaction is normally very slow but is catalysed by manganese oxide
  • Use different catalysts
26
Q

Hydrogen Peroxide Experiment Equation

A

2H2O2 —> 2H2O + O2

-The catalyst is not in the equation as it’s unchanged

27
Q

Colour of manganese oxide

A

Black Solid

28
Q

Hydrogen Peroxide Experiment Variables

A

Input: Which catalyst is used
Output: Volume of O2
Controls: Temp, Mass and SA of mg, Conc and Vol of H2O2

29
Q

Hydrogen Peroxide Experiment Results

A
  • More effective catalysts increase rate more effectively (steeper line)
  • All lines flatten out eventually
30
Q

Disappearing Cross

A

Used to show when a material is formed and makes liquid opaque

31
Q

Gas Syringe

A

Measures amount of gas produced, very accurate and easy to read, gas could leak or move too quickly

32
Q

Mass lost

A

Measures how much mass has left the conical flask (gas), easy to set up, could lose gas before timer starts

33
Q

Collecting gas underwater

A

Measures amount of gas produced, can get easy readings, gas may dissolve or leak, hard to read

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