The Rate and Extent of Chemical Change

Question 1

What are the two ways to measure the rate of reaction?

Answer 1

• How fast a reactant is used up
• How fast a product is made

Question 2

What are the three methods used to determine the rate of reaction?

Answer 2

• Mass loss
• Gas collection
• Precipitation

Question 3

What is the formula for calculating the rate of reaction?

Answer 3

Rate = amount of reactant used or Rate = amount of product made / time taken

Question 4

What are the units for rate when mass is measured in grams?

Answer 4

g/s

Question 5

What are the units for rate when volume is measured in cm³?

Answer 5

cm³/s

Question 6

In the mass loss method, what happens to the mass when a gas is produced?

Answer 6

The mass decreases

Question 7

What is the limitation of the mass loss method?

Answer 7

The gas must be sufficiently dense to measure the change in mass

Question 8

What is the gas collection method used for?

Answer 8

To trap and measure the volume of gas produced over time

Question 9

What is a common setup for gas collection?

Answer 9

Downward displacement of water or using a gas syringe

Question 10

What occurs in precipitation reactions?

Answer 10

A solid precipitate forms when two clear solutions are mixed

Question 11

What is the disappearing cross experiment?

Answer 11

Measuring the time taken for a precipitate to block a cross from view

Question 12

What are the units for rate when expressed in terms of moles?

Answer 12

mol/s

Question 13

How can rate of reaction be expressed in terms of moles from mass?

Answer 13

mass per unit time ÷ molar mass of the substance

Question 14

How can rate of reaction be expressed in terms of moles from volume?

Answer 14

volume per unit time ÷ molar gas volume (24,000 cm³/mol)

Question 15

What is plotted on the x-axis of a rate graph?

Answer 15

Time

Question 16

What does a straight line graph through the origin indicate?

Answer 16

The relationship is directly proportional

Question 17

What does a steeper gradient on a rate graph indicate?

Answer 17

A faster rate of reaction

Question 18

What happens to the rate of reaction as reactants are used up?

Answer 18

The rate slows down and the graph becomes less steep

Question 19

How can the mean rate of reaction be calculated?

Answer 19

Total change in volume / total time taken

Question 20

What is the formula for calculating the gradient at a point on a curve?

Answer 20

gradient = change in product / change in time

Question 21

What are the factors that affect the rate of reaction?

Answer 21

• Concentration of reactants or pressure of gases
• Temperature of the reaction
• Surface area of solid reactants
• Presence of a catalyst

Question 22

What is the effect of increasing concentration or pressure on the rate of reaction?

Answer 22

Increases the rate of reaction

Question 23

What factors influence the rate of a reaction?

Answer 23

The concentration of reactants, temperature, surface area of solid reactants, presence of a catalyst.

Question 24

True or False: Increasing the concentration of a solution or gas pressure decreases the rate of reaction.

Answer 24

False

Question 25

How does increasing temperature affect the rate of reaction?

Answer 25

It increases the rate of reaction because the particles have more kinetic energy.

Question 26

What effect does increasing surface area have on the rate of reaction?

Answer 26

It increases the rate of reaction.

Question 27

What is the activation energy?

Answer 27

The minimum amount of energy needed for a reaction to occur.

Question 28

Fill in the blank: A _______ collision means that the reactant particles have sufficient energy to react.

Answer 28

successful

Question 29

Fill in the blank: A _______ collision means that the reactant particles have insufficient energy.

Answer 29

unsuccessful

Question 30

What happens to the rate of reaction when a catalyst is added?

Answer 30

It increases the rate of reaction.

Question 31

What is the relationship between particle size and surface area?

Answer 31

Surface area increases as particle size decreases.

Question 32

True or False: Catalysts are consumed in the reaction.

Answer 32

False

Question 33

What is one practical method to investigate the effect of concentration on the rate of reaction?

Answer 33

Measuring the formation of a precipitate.

Question 34

List the materials needed for measuring turbidity in a reaction.

Answer 34

* Sodium thiosulfate solution * Dilute hydrochloric acid * Conical flask * Black cross on paper * Stopwatch

Question 35

What is the conclusion of the required practical investigating the effect of concentration on the rate of reaction?

Answer 35

As there are more reactant particles in a given volume, collisions occur more frequently, increasing the rate of reaction.

Question 36

How does increasing pressure affect the rate of reaction?

Answer 36

It increases the rate of reaction by causing more collisions per second.

Question 37

Describe the effect of temperature on reaction rate.

Answer 37

Increasing temperature increases the kinetic energy of particles, leading to more frequent and successful collisions.

Question 38

What is the general rule regarding temperature increase and reaction rate?

Answer 38

For every 10 °C increase in temperature, the rate of reaction approximately doubles.

Question 39

What is the role of catalysts in chemical reactions?

Answer 39

They provide an alternative pathway with lower activation energy.

Question 40

True or False: Catalysts are part of the chemical equation.

Answer 40

False

Question 41

What type of catalysts are commonly used in industry?

Answer 41

Transition metals.

Question 42

Fill in the blank: Catalysts _______ the rate of reaction without being altered.

Answer 42

speed up

Question 43

What is the effect of increasing surface area on the rate of reaction?

Answer 43

It causes more collisions per second, increasing the rate of reaction.

Question 44

What happens to the rate of reaction as the concentration of reactants increases?

Answer 44

The rate of reaction increases due to more frequent collisions.

Question 45

Explain the concept of collision theory.

Answer 45

Chemical reactions occur when reactant particles collide with sufficient energy to react.

Question 46

What is the result of successful collisions?

Answer 46

Reactant particles rearrange to form products.

Question 47

What are reversible reactions?

Answer 47

Reversible reactions are those where the product molecules can react with each other or decompose to form the reactant molecules again.

Question 48

What is the difference between the forward and reverse reactions in a reversible reaction?

Answer 48

The forward reaction forms the products, while the reverse reaction forms the reactants.

Question 49

What happens to ammonium chloride when heated?

Answer 49

Heating ammonium chloride produces ammonia and hydrogen chloride gases.

Question 50

What type of process is the heating of ammonium chloride?

Answer 50

The heating of ammonium chloride is an endothermic process.

Question 51

What occurs when hot gases from ammonium chloride cool down?

Answer 51

The hot gases recombine to form solid ammonium chloride, which is an exothermic process.

Question 52

What is water of crystallisation?

Answer 52

Water of crystallisation is the water included in the structure of some salts during the crystallisation process.

Question 53

What is anhydrous salt?

Answer 53

Anhydrous salts are those that have lost their water of crystallisation, usually by heating.

Question 54

What is the state of a system at equilibrium?

Answer 54

At equilibrium, the rate of the forward reaction equals the rate of the reverse reaction.

Question 55

What does it mean for equilibrium to be dynamic?

Answer 55

In a dynamic equilibrium, the molecules on both sides of the equation are constantly changing into each other at the same rate.

Question 56

What conditions must be met for equilibrium to occur?

Answer 56

Equilibrium occurs in a closed system where none of the participating chemical species can leave or enter.

Question 57

What is Le Chatelier's Principle?

Answer 57

Le Chatelier's Principle states that when a change is made to the conditions of a system at equilibrium, the system automatically moves to oppose the change.

Question 58

How does increasing the concentration of a reactant affect equilibrium?

Answer 58

Increasing the concentration of a reactant shifts the equilibrium to the right, making more product.

Question 59

How does decreasing the concentration of a reactant affect equilibrium?

Answer 59

Decreasing the concentration of a reactant shifts the equilibrium to the left, making less product.

Question 60

What happens to equilibrium when the temperature of a reaction increases?

Answer 60

The equilibrium shifts in the direction of the endothermic reaction.

Question 61

What happens to equilibrium when the temperature of a reaction decreases?

Answer 61

The equilibrium shifts in the direction of the exothermic reaction.

Question 62

What effect does increasing pressure have on a gaseous reaction?

Answer 62

Increasing pressure will favor the reaction that produces the least number of gas molecules.

Question 63

What happens if there are the same number of moles of gases on either side of the equation when pressure changes?

Answer 63

There is no effect on the position of equilibrium when pressure is changed.

Question 64

What is a common example of a reaction reaching equilibrium?

Answer 64

The reaction between H2 and N2 in the Haber process is a common example.

Question 65

Predict the effect of increased pressure on the equilibrium of the reaction 2NO2 (g) ⇌ N2O4 (g).

Answer 65

The equilibrium will shift to the right, favoring the production of N2O4.

Question 66

What is the outcome when the concentration of ICl or Cl2 is increased in the reaction ICl (l) + Cl2 (g) ⇌ ICl3 (s)?

Answer 66

The equilibrium will shift to the right, producing more ICl3.

Question 67

Fill in the blank: The forward reaction in a reversible reaction is _______ in one direction and _______ in the opposite direction.

Answer 67

exothermic, endothermic