C7 Flashcards
Draw an exothermic reaction profile?
draw
Draw an endothermic reaction profile?
draw
draw an electrolysis cell?
draw
Advantages of hydrogen fuel cells
- They will produce electricity for as long as you provide hydrogen
- Hydrogen fuel cells do not get less efficient the longer they run
Bond Energy Formula?
energy change = sum of the energy needed to break bonds (reactants) - energy released when new bonds are formed (products)
Characteristics of fuel cells?
- reliable
- efficient
- compact and lightweight
- not very polluting
Disadvantages of hydrogen fuel cells
- Highly Explosive
- They produce a relatively low potential difference or voltage so several are needed together
Electrolysis and photosynthesis is an example of a _____.
endothermic reaction
Example of a endothermic reaction
citric acid + sodium hydrogencarbonate
Example of reactive profile diagram with catalyst
draw
How can rechargeable batteries be recharged?
The chemical reactions can be reversed when an electrical current is applied.
How does the reactivity of the metals link to the potential difference of the metals?
The greater the difference between the reactivity of the metals, the greater the potential difference produced by the cell.
How is a electrochemical cell set up?
1) 2 electrodes which are metals as they must conduct electricity
2) The electrolyte is a liquid that contains ions
3) Wire connecting the 2 electrodes
If the energy change on an energy level diagram is negative, is this an endothermic or exothermic reaction?
Exothermic reactions have a negative energy change because they release/lose energy.
In an ____ reaction, the energy of the reactants is higher than the energy of the products.
exothermic
In exothermic reactions the energy released by forming bonds is ____ than the energy used to break them.
greater
Is bond breaking endothermic or exothermic?
endothermic
Melting is an example of an _____.
Endothermic reaction. Energy is taken in from the surroundings.
Name 2 different types of reactions which are exothermic
- Neutralisation
- Combustion
Types of batteries
- rechargeable
= non-rechargeable
What can we do to change the voltage output of a cell?
- change the electrodes
- change the electrolyte
What do catalysts do to the activation energy?
Catalysts increase reaction rates by lowering the activation energy
What is a battery?
A battery contains 2 or more cells connected in series, to produce a greater voltage.
What is a chemical cell?
A chemical cell is a source of electrical energy.
What is a fuel cell?
A fuel cell is an electrical cell that’s supplied with a fuel and oxygen which uses energy from the reaction between them to provide electrical energy efficiently.
What is a reaction profile diagram?
Reaction profiles are diagrams that show the energies of the reactants and products in a reaction and how they change over the course of the reaction.
What is activation energy?
Activation energy is the amount of energy required to start a chemical reaction
What is an electrolyte?
A solution that can conduct electricity, usually an ionic compound
What is an endothermic reaction?
An endothermic reaction is a reaction where energy is drawn in from the surroundings, causing the surroundings and object to cool down.
What is an exothermic reaction?
An exothermic reaction is a reaction which cools itself down, giving heat to the surroundings.
What is an instant cold ice pack an example of?
An endothermic process
What is the only waste product in a hydrogen fuel cell?
water
What type of process is the breaking of existing bonds?
endothermic
What type of process is the forming of new bonds?
exothermic
Which energy resource uses falling water to generate electricity?
Hydroelectricity
Why are fuel cells reliable?
They have no moving parts
Why can alkaline batteries not be recharged?
The reaction isnt reversible
Why do alkaline batteries eventually stop working?
A reactant is used up
