| What type of reaction is it when there is a negative energy change? | Exothermic (since it show energy is given out) |
| What type of reaction is it when there is a positive energy change? | Endothermic ( since it shows energy is taken in) |
| Give three type of reactions which are exothermic | Respiration
Combustion
Neutralization |
| Give an example of a reaction which is endothermic | Photosynthesis |
| Breaking bonds ____ ____ energy and making bonds ____ ____ energy | Take in energy
Release energy |
| How can you decide if a reaction is exothermic? | If the energy taken in to break bonds is less than the energy released in making bonds the reaction is exothermic |
| How can you decide if a reaction is endothermic? | If the energy taken to break bonds is greater than the energy released when making bonds then the reaction is endothermic. |
| How do you calculate energy change in a reaction? | Energy in - Energy out |
| How does a cell using electrolysis work? | Electrodes which are made out of two different metals, the more reactive metal among them will form ions by giving up electrons which go through the wire to the other electrode.
Since there a flow of electrons through the a current is formed. |
| How does a hydrogen fuel cell work? | In the positive pole oxygen atoms accept electrons to form OH ions.
In the negative pole hydrogen loses electrons to the OH ions to form water.
Overall reaction is that hydrogen and oxygen combine to give water |
| Give three advantages of using hydrogen cells. | Only water is formed hence no pollutants.
The reaction gives out plenty of energy
There is plenty of hydrogen so we will not run out |
| Give one drawback of using hydrogen cells | Hydrogen is very flammable, hence if lighted up can result in an explosion |
| What is a reversible reaction? | A reaction with both a forward reaction as well as a backward reaction, where a product can form then break down. |
| What is meant by equilibrium? | The state where the forward and back reaction is taking place at the same rate in a reversible reaction so there is no overall change. |
| How does changing the temperature affect equilibrium? | If the forward reaction is exothermic increasing the temperature decreases the yield but if it is endothermic increasing the temperature increases the yield |
| How does changing the pressure affect equilibrium? | If there are fewer products than reactants increasing pressure increases the yield |
| How does removing the product of forward reaction affect equilibrium? | More product will form in order to restore the balance |
| How does adding a catalyst affect equilibrium ? | The catalyst will speed up both forward and back reaction equally |
| What are the optimum conditions for best yield? | High pressure, removal of product from forward reaction
Moderate temperature and a catalyst |
| How can equilibrium be reached faster? | By raising the temperature and pressure then adding a catalyst |
| How can you shift equilibrium when reaction takes place in solution? | By adding more of the reactant ( increasing its concentration) so more product will form
By changing temperature ( a rise in temperature will favor endothermic reaction) |
