Chapter 2 and 3 theory

Question 1

What is the formula for calculating energy transformation efficiency during combustion?

Answer 1

% efficiency= amount of potential energy in chemical form / amount of energy in useful form
×100

Question 2

What does the specific heat capacity (c) represent

Answer 2

The specific heat capacity (c) represents the energy needed to raise the temperature of 1 gram of a substance by 1 degree Celsius.

Question 3

What is solution calorimetry?

Answer 3

Solution calorimetry is the process of using a calorimeter to measure heat changes in a solution, such as heat of dissolution and neutralization reactions.

Question 4

What is a calorimeter?

Answer 4

A calorimeter is an apparatus used to measure heat changes during a chemical reaction or change of state.

Question 5

What is meant by “change in enthalpy”?

Answer 5

Change in enthalpy refers to the amount of energy released or absorbed in a chemical reaction.

Question 6

What does it mean to “calibrate” an instrument?

Answer 6

To “calibrate” an instrument means adjusting it using standards of known measurements to ensure the instrument’s accuracy.

Question 7

What is a calibration factor?

Answer 7

A calibration factor is the amount of energy required to change the contents of a calorimeter by one degree, with units of J °C⁻¹.

Question 8

What is electrical calibration?

Answer 8

Electrical calibration is the calibration of a calorimeter by supplying a known quantity of electricity.

Question 9

What is chemical calibration?

Answer 9

Chemical calibration is the calibration of a calorimeter using a combustion reaction with a known ∆H (enthalpy change).

Question 10

What are primary galvanic cells?

Answer 10

Primary galvanic cells are non-rechargeable cells that convert chemical energy into electrical energy. They are discarded once the voltage becomes too low to generate electricity.

Question 11

Describe the design features of a dry cell.

Answer 11

A dry cell consists of a zinc container filled with an electrolyte paste containing manganese(IV) oxide, zinc chloride, ammonium chloride, and water. A carbon rod embedded in the paste forms the cathode, while the zinc container serves as the anode.

Question 12

What distinguishes an alkaline zinc manganese dioxide cell from a dry cell?

Answer 12

Alkaline cells use a powdered zinc anode in an electrolyte paste of potassium hydroxide and have a cathode composed of manganese dioxide and graphite. They provide a greater current output and longer shelf life compared to dry cells.

Question 13

What are the main features of lithium batteries?

Answer 13

Lithium batteries use lithium anodes and can produce a high voltage. They have a longer shelf life and are mainly used in electronic memory, electronic switchboards, navigation systems, and other devices requiring long-term power.

Question 14

What are fuel cells, and how do they operate?

Answer 14

Fuel cells are electrochemical cells that convert chemical energy from a fuel directly into usable DC electricity and heat through redox reactions. Fuel passes over the anode, where it is split into ions and electrons. The electrons flow through an external circuit, while the ions move through the electrolyte towards the cathode. At the cathode, ions combine with oxygen to produce by-products, typically water.

Question 15

What is a solid oxide fuel cell (SOFC), and what is its main characteristic?

Answer 15

A solid oxide fuel cell (SOFC) uses a ceramic (solid oxide) electrolyte that conducts O2− ions at high temperatures. Oxygen gas is reduced at the cathode to produce oxide ions that travel through a ceramic material, like zirconia, to the anode, where they react with hydrogen ions from the oxidized fuel to make water.

Question 16

What distinguishes a proton exchange membrane fuel cell (PEMFC)?

Answer 16

A proton exchange membrane fuel cell (PEMFC) offers high power density and operates at relatively low temperatures. It uses a polymer membrane as its electrolyte, eliminating corrosion and safety concerns associated with liquid electrolyte fuel cells.

Question 17

What is a direct methanol fuel cell (DMFC)?

Answer 17

A direct methanol fuel cell (DMFC) is powered by liquid methanol and is suitable for mobile phones, portable music devices, and laptops due to its small size and low operating temperature. It does not require a fuel reformer, allowing devices to operate for longer periods of time.

Question 18

What is the main characteristic of an alkaline fuel cell (AFC)?

Answer 18

The alkaline fuel cell (AFC), also known as the hydrogen-oxygen fuel cell, uses potassium hydroxide as the electrolyte. The alkaline environment allows the use of non-precious metal catalysts, significantly reducing the cost of the fuel cell system.

Question 19

What factors are important in the design of electrodes for fuel cells?

Answer 19

Electrodes in fuel cells need to be designed to maximize surface area for oxidation and reduction reactions to take place efficiently. This is achieved by making the electrodes porous to provide greater surface area. Additionally, catalysts may be embedded in the electrodes to facilitate reactions at lower temperatures. Materials such as platinum, nickel, palladium, and graphene are commonly used as catalysts, depending on the reactions occurring, the electrolyte used, and the operating conditions of the fuel cell.

Question 20

What

What are the primary cells

Answer 20

• the dry cell
• the alkaline zinc manganese dioxide cell
• lithium batteries

Question 21

What are the fuel cells

Answer 21

• solid oxide cell
• proton exchange fuel cell (PEMFC)
• Direct methanol fuel cells (DMFC)
• Alkaline fuel cell (AFC)

Question 22

What are the green energy principles concerning energy production and consumption?

Answer 22

Improving efficiency, utilizing renewable feedstocks, considering energy in design viability, waste reduction, and recycling, and minimizing emissions are key principles

Question 23

What is an alkaline fuel cell (AFC)?

Answer 23

An AFC is a type of fuel cell that converts oxygen from the air and hydrogen from a supply into electrical energy and heat.

Question 24

How does energy loss occur in electricity generation and transmission?

Answer 24

Energy loss occurs during conversions and transmission, typically resulting in only around 10% of energy from the power station reaching the customer.

Question 25

How do fuel cells reduce energy waste

Answer 25

Fuel cells reduce energy waste by enabling stationary power systems, minimizing energy transformations, employing catalytic electrodes, and utilizing generated heat for various applications

Question 26

What considerations are afforded in energy production and consumption?

Answer 26

Considerations include reducing hazards and pollutants, preventing waste, degrading chemicals, improving atom economy, and using catalysts for efficient reaction pathways

Question 27

What are the key aspects of efficient fuel cell design?

Answer 27

Efficient fuel cell design involves even distribution of fuel and oxidizing agents, constant temperature maintenance, minimized power loss, and proper sealing to prevent gas leakage

Question 28

What is an electrolyte-free fuel cell (EFFC)?

Answer 28

An EFFC is a new energy device replacing current solid oxide fuel cells, offering higher efficiency and the ability to electrolyze water to produce hydrogen fuel.

Question 29

What distinguishes EFFC technology from current SOFCs

Answer 29

EFFC technology offers increased oxide ion conductivity, operates at lower temperatures, experiences lower voltage losses, is more efficient, and is cheaper to produce.

Question 30

Why is hydrogen considered environmentally friendly in fuel cell technology?

Answer 30

Hydrogen is considered environmentally friendly because it produces net zero carbon emissions when used in fuel cells

Question 31

What are the methods for producing hydrogen gas from water?

Answer 31

Methods include thermochemical splitting, photodecomposition, and electrolysis.

Question 32

How does electrolysis of water produce hydrogen?

Answer 32

Electrolysis decomposes water into pure oxygen and hydrogen using sustainable energy resources such as solar, wind, and biomass.

Question 33

How can alcohols be used to produce hydrogen gas?

Answer 33

Alcohols like ethanol can be used to produce hydrogen gas through steam reforming or direct catalytic conversion in fuel cells.

Question 34

How can biomass be used for hydrogen production?

Answer 34

Biomass can be enzymatically converted into glucose and further processed to produce hydrogen gas.

Question 35

What is a major challenge in the use of hydrogen as a fuel?

Answer 35

Storage is a major challenge due to hydrogen’s low energy content by volume, requiring extreme compression or liquefaction.

Question 36

What is a challenge in alcohol production from plants?

Answer 36

Maximizing the conversion of organic material into alcohol presents a challenge, particularly in gas fermentation.

Question 37

What are the drawbacks of using algae for fuel production?

Answer 37

Drawbacks include the need for treatment of larger species and difficulties in harvesting microscopic algae.