Chapter 7

Question 1

Describe physical and chemical changes and the differences between them

Answer 1

A physical change affects the forces between particles, however the particles and their chemical properties remain the same. Also being reversible. While chemical changes change the particles themselves. For example, forming OH from H2O. Chemical changes include colour change, odour, effervescence and temperature change (from energy being taken in or out).

Question 2

State the effect of concentration, particle size, catalysts and temperature on the rate of reactions

Answer 2

concentration increases; rate of reaction increases
particle size increases; rate of reaction decreases
temperature increases; rate of reaction increases
catalysts present; rate of reaction increases

Question 3

State the effect of concentration on rate of reaction

Answer 3

a high concentration increases the chance for more successful collisions as there are a lot more reacting particles in the same volume.

Question 4

State the effect of temperature on rate of reaction

Answer 4

a high temperature means that the particles would have more energy (than the activation energy required) and therefore there are more successful collisions. Including more collisions as the particles have more kinetic energy.

Question 5

State the effect of particle size on rate of reaction

Answer 5

the smaller the particle size, the more surface area is exposed. This allows more particles to be in contact with the other particles and therefore more successful collisions are possible.

Question 6

State the effect of catalysts on rate of reaction

Answer 6

catalysts increase the rate of reaction as they provide a collision with lower activation energy required, therefore there are more successful collisions as not as much activation energy is required.

Question 7

Danger when it comes to particle size, concentration and rate of reaction

Answer 7

the effect of particle size can sometimes be dangerous. If a powdered substance ignites in the presence of air, it can cause an explosion. Explosions are caused by the large surface area of the particles and the very fast rate of combustion. For methane, it can be found in high concentrations in caves. It can be proven to be highly flammable.

Question 8

How to investigate rate of reaction with a gas

Answer 8

You have to determine how much of the gas product is produced (using a gas syringe or cylinder in a trough of water) over a certain period of time and divide it by that. That will give your rate of reaction, of which should have the unit cm^3/s.

Question 9

How to investigate rate of reaction with a precipitate

Answer 9

add a black cross below a beaker containing one reactant, add the other reactant and record the time it takes for the cross to disappear.

Question 10

How to investigate rate of reaction with a reactants

Answer 10

The mass of the reactants would decrease. Therefore, you do so by measuring the mass of reactants on a digital balance at regular time intervals.

Question 11

photochemical reactions

Answer 11

reactions initiated by light

Question 12

lights affect on the rate of photochemical reactions

Answer 12

as light intensity increase, so does the rate of photochemical reactions

Question 13

How are silver salts used in photography?

Answer 13

Silver chloride is light sensitive and breaks down to form silver metal with is black (reduction). the more intense the light is on the film, the faster the rate of reaction so a darker photo appears.

Question 14

photosynthesis

Answer 14

the reaction between carbon dioxide and water in the presence of chlorophyll and sunlight (energy) to produce glucose and oxygen

Question 15

Oxidation

Answer 15

Gain of oxygen

Question 16

Reduction

Answer 16

Loss of oxygen

Question 17

Redox Reaction

Answer 17

the transfer of electrons from two elements, involving both a reduction and oxidation reaction

Question 18

How does one identify redox reactions?

Answer 18

When the oxidation states change for an element

Question 19

State the colour change occurs when potassium manganate (VII) is reduced

Answer 19

purple and turns colourless

Question 20

State the colour change occurs when potassium iodide is oxidised

Answer 20

colourless to brown

Question 21

oxidising agent

Answer 21

a substance which oxidises another substance during a redox reaction

Question 22

reducing agent

Answer 22

a substance which reduces another substance during a redox reaction.

Question 23

describe the effects of heat and water on anhydrous and hydrous cobalt(II) chloride by changing the reaction conditions.

Answer 23

Anhydrous cobalt (II) chloride + water ----> hydrated cobalt (II) chloride [blue to pink]
Add water for the products to form and heat it up (to evaporate water) for the reactants to form.

Question 24

Dynamic Equilibrium

Answer 24

A system in a steady state since forward reaction and backward reaction occur at the same rate

Question 25

If the concentration of reactants increases__

Answer 25

Equilibrium shifts to the right and increases product yield (Removes additional added reactant)

Question 26

If the concentration of product increases__

Answer 26

Equilibrium shifts to the left and decreases in product yield (Removes additional product)

Question 27

If the pressure in an equilibrium increases__

Answer 27

will move in the direction of fewest moles due to that restoring equilibrium and reduce the pressure. For example: 2 mol Ammonia and 4 moles Nitrogen and Hydrogen, it moves to the Ammonia.

Question 28

The Haber Process

Answer 28

Hydrogen and Nitrogen form Ammonia, with iron as a catalyst

Question 29

Addition of catalyst to reaction___

Answer 29

only increases the rate of reaction

Question 30

if the temperature increases in a exothermic and endothermic reaction__

Answer 30

Moves to endothermic side. It will increase product yield.

Question 31

describe the effects of heat and water on anhydrous and hydrous copper(II) sulfate and by changing the reaction conditions.

Answer 31

Anhydrous copper (II) sulphate + water ----> hydrated copper (II) sulphate [white to blue]
Add water for the products to form and heat it up (to evaporate water) for the reactants to form.

Question 32

dynamic equilibrium

Answer 32

The rate of the forward reaction is equal to the rate of the reverse reaction and at this point there is no change in the proportion of reactants or products.