rates (p2)

Question 1

What is rate of reaction?

Answer 1

A measure of how quickly reactants turn into product

Question 2

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

Answer 2

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

Question 3

What are the units of rate of reaction?

Answer 3

g/s
or
cm³/s

Question 4

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

Answer 4

g

Question 5

What are the units for volume

Answer 5

cm³

Question 6

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

Answer 6

fast reaction

Question 7

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

Answer 7

the reaction is complete and no more product is produced

Question 8

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] How can the actual rate of reaction be determined from a rate of reaction graph?

Answer 8

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

Question 9

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] What is the equation for measuring the gradient?

Answer 9

change in y ÷ change in x

Question 10

What is pressure?

Answer 10

A measure of how close together gas particles are

Question 11

What is concentration?

Answer 11

The number of particles in a given volume

Question 12

What is surface area?

Answer 12

The area of a solid that is exposed to the surface

Question 13

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

Answer 13

Break it into smaller pieces

Question 14

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

Answer 14

magnesium powder

Question 15

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

Answer 15

rate increases

Question 16

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

Answer 16

rate increases

Question 16

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

Answer 16

rate increases

Question 17

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

Answer 17

rate increases

Question 17

What methods can you use to collect a gas?

Answer 17

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

Question 17

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

Answer 17

rate increases

Question 18

What piece of apparatus should be used to measure 20 cm³ of acid?

Answer 18

Measuring cylinder

Question 19

When will solutions turn cloudy?

Answer 19

When an insoluble solid is produced

Question 20

What are the independent and dependent variables in the investigation: 𝑨 𝒔𝒕𝒖𝒅𝒆𝒏𝒕 𝒎𝒆𝒂𝒔𝒖𝒓𝒆𝒔 𝒕𝒉𝒆 𝒕𝒊𝒎𝒆 𝒕𝒂𝒌𝒆𝒏 𝒇𝒐𝒓 𝒂 𝒄𝒓𝒐𝒔𝒔 𝒕𝒐 𝒅𝒊𝒔𝒂𝒑𝒑𝒆𝒂𝒓 𝒘𝒉𝒆𝒏 𝒅𝒊𝒇𝒇𝒆𝒓𝒆𝒏𝒕 𝒄𝒐𝒏𝒄𝒆𝒏𝒕𝒓𝒂𝒕𝒊𝒐𝒏𝒔 𝒐𝒇 𝒔𝒐𝒅𝒊𝒖𝒎 𝒕𝒉𝒊𝒐𝒔𝒖𝒍𝒇𝒂𝒕𝒆 𝒂𝒓𝒆 𝒖𝒔𝒆𝒅?

Answer 20

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

Question 20

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

Answer 20

the solution turns cloudy when the product is formed. Measuring the time allows us to do 𝙦𝙪𝙖𝙣𝙩𝙞𝙩𝙮 𝙤𝙛 𝙥𝙧𝙤𝙙𝙪𝙘𝙩 𝙛𝙤𝙧𝙢𝙚𝙙 ÷ 𝙩𝙞𝙢𝙚

Question 21

What are the independent and dependent variables in the investigation: 𝑨 𝒔𝒕𝒖𝒅𝒆𝒏𝒕 𝒎𝒆𝒂𝒔𝒖𝒓𝒆𝒔 𝒕𝒉𝒆 𝒗𝒐𝒍𝒖𝒎𝒆 𝒐𝒇 𝒈𝒂𝒔 𝒑𝒓𝒐𝒅𝒖𝒄𝒆𝒅 𝒘𝒉𝒆𝒏 𝒅𝒊𝒇𝒇𝒆𝒓𝒆𝒏𝒕 𝒄𝒐𝒏𝒄𝒆𝒏𝒕𝒓𝒂𝒕𝒊𝒐𝒏𝒔 𝒐𝒇 𝒉𝒚𝒅𝒓𝒐𝒄𝒉𝒍𝒐𝒓𝒊𝒄 𝒂𝒄𝒊𝒅 𝒂𝒓𝒆 𝒖𝒔𝒆𝒅?

Answer 21

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

Question 21

What variables should be controlled in the investigation: 𝑨 𝒔𝒕𝒖𝒅𝒆𝒏𝒕 𝒎𝒆𝒂𝒔𝒖𝒓𝒆𝒔 𝒕𝒉𝒆 𝒕𝒊𝒎𝒆 𝒕𝒂𝒌𝒆𝒏 𝒇𝒐𝒓 𝒂 𝒄𝒓𝒐𝒔𝒔 𝒕𝒐 𝒅𝒊𝒔𝒂𝒑𝒑𝒆𝒂𝒓 𝒘𝒉𝒆𝒏 𝒅𝒊𝒇𝒇𝒆𝒓𝒆𝒏𝒕 𝒄𝒐𝒏𝒄𝒆𝒏𝒕𝒓𝒂𝒕𝒊𝒐𝒏𝒔 𝒐𝒇 𝒔𝒐𝒅𝒊𝒖𝒎 𝒕𝒉𝒊𝒐𝒔𝒖𝒍𝒇𝒂𝒕𝒆 𝒂𝒓𝒆 𝒖𝒔𝒆𝒅?

Answer 21

- volume of sodium thiosulfate - concentration of hydrochloric acid - volume of hydrochloric acid - same cross - temperature

Question 22

What is collision theory?

Answer 22

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

Question 23

What is the activation energy?

Answer 23

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

Question 24

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

Answer 24

no reaction - they stay as reactants

Question 25

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

Answer 25

they are converted into products

Question 26

What does the term 𝒇𝒓𝒆𝒒𝒖𝒆𝒏𝒄𝒚 𝒐𝒇 𝒄𝒐𝒍𝒍𝒊𝒔𝒊𝒐𝒏𝒔 mean?

Answer 26

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

Question 27

How can you increase the rate of a reaction?

Answer 27

1. increase the frequency of collisions 2. increase the energy of collisions

Question 28

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

Answer 28

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

Question 29

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

Answer 29

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

Question 30

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

Answer 30

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

Question 31

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

Answer 31

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

Question 32

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

Answer 32

rate doubles

Question 33

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

Answer 33

rate halves

Question 34

What are catalysts?

Answer 34

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

Question 35

Why are catalysts not included in chemical equations?

Answer 35

they are not used up or produced in chemical reactions

Question 36

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

Answer 36

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

Question 37

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

Answer 37

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

Question 38

What does this symbol ⇌ mean?

Answer 38

a reversible reaction

Question 39

What is a reversible reaction?

Answer 39

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

Question 40

How can the direction of a reversible reaction be changed?

Answer 40

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

Question 41

What is an exothermic reaction?

Answer 41

A reaction that transfers energy to the surroundings

Question 42

What is an endothermic reaction?

Answer 42

A reaction that takes in energy from the surroundings

Question 43

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

Answer 43

Endothermic

Question 44

What is dynamic equilibrium?

Answer 44

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

Question 45

What conditions are needed for dymanic equilibrium to be reached?

Answer 45

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

Question 46

What is a closed system?

Answer 46

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

Question 47

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] How does a system at equilibrium respond to changes?

Answer 47

* 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

Question 48

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] What is Le Chatelier's Principle?

Answer 48

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

Question 49

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] If the temperature increases, how will a system at equilibrium respond?

Answer 49

System will decrease the temperature

Question 50

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] If the temperature of a system at equilibrium decreases, how will the system respond?

Answer 50

System will increase the temperature

Question 51

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] If the temperature of a system at equilibrium increases, will the exothermic or endothermic reaction be favoured?

Answer 51

Endothermic reaction

Question 52

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] If the temperature of a system at equilibrium decreases, will the exothermic or endothermic reaction be favoured?

Answer 52

Exothermic reaction

Question 53

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] If the concentration of a reactant is increased in a system at equilibrium, which reaction is favoured?

Answer 53

The forward reaction

Question 54

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] If the concentration of a reactant is decreased in a system at equilibrium, which reaction is favoured?

Answer 54

The reverse reaction

Question 55

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] If the concentration of a product is increased in a system at equilibrium, which reaction is favoured?

Answer 55

The reverse reaction

Question 56

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] If the concentration of a product is decreased in a system at equilibrium, which reaction is favoured?

Answer 56

The forward reaction

Question 57

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] If the rate of the forward reaction increases in a reversible system, what will happen to the concentration of reactants and products?

Answer 57

* Concentration of reactants decrease * Concentration of products increase

Question 58

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] If the pressure is increased in a system at equilibrium, which reaction is favoured?

Answer 58

the reaction which produces fewer molecules of gas

Question 59

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] If the pressure is decreased in a system at equilibrium, which reaction is favoured?

Answer 59

the reaction which produces more molecules of gas

Question 60

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] 𝗡₂𝗢₄ (𝗴) ⇌ 𝟮 𝗡𝗢₂ (𝗴) Which reaction will be favoured if the pressure increases?

Answer 60

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

Question 61

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] What does yield mean?

Answer 61

How much of a substance is produced