1. How many grams of carbon are needed in the following reaction in order to produce 8755 kJ? This is an image of a chemical equation C O2 reaction arrow CO2 Delta h -39292 kJmol

2. How much energy is contained in each of the following?

3 moles of chlorine molecules
5 moles of ammonia molecules
4.8 moles of propane
3. Make an energy diagram for the heat formation of one mole of each of the following substances:

This is an image of a chemical equation H2 I2 reaction arrow 2HI
This is an image of a chemical equation 2H2 CO reaction arrow CH3OH
This is an image of a chemical equation C 2H2 reaction arrow CH4
4. If the change in enthalpy for carbon monoxide (CO) is -104.5 kJ/mol, and that of carbon dioxide (CO2) is -392.92 kJ/mol, what can we conclude about the stability of these two substances?

5. Calculate the change in enthalpy for the following reactions:

This is an image of a chemical equation C2H6 O2 reaction arrow CO2 H2O
This is an image of a chemical equation C25H52 O2 reaction arrow CO2 H2O
This is an image of a chemical equation N2 H2 reaction arrow NH3
This is an image of a chemical equation C O2 reaction arrow CO
6. Find the enthalpy for the combustion of combustion of methanol.

7. Methylhydrazine is commonly used as a liquid rocket fuel. Its combustion is indicated by the following reaction.

This is an image of a chemical equation N2H3CH3 O2 reaction arrow N2 CO2 H2O

Balance this equation.
Calculate ΔH for this reaction.
8. The heat of combustion of hydrogen gas per gram is about 2.5 times that of natural gas. The main component of natural gas is methane gas.

Also, the combustion of hydrogen is “cleaner” than that of natural gas, since the only product is water. Thus, it seems a likely choice for a major fuel source in the future.

Prove that the heat of combustion of hydrogen per gram is about 2.5 times that of natural gas. Begin by calculating the heat associated with the combustion of each fuel in kJ/g of fuel.

but know think of it in terms of bond breaking and bond making.

h–h + h–h + o=o ==> h–o–h + h–o–h

as you can see from the diagram, theoretically, more energy is released by forming water, than was absorbed in breaking up the original hydrogen and oxygen molecules.

the energy level of the fuel + oxygen is higher than that of water.

therefore the fuel + oxygen mixture has the potential to release potential chemical energy as heat energy or, crucially, electrical energy, if the reaction can be made to go via  oxidation and reduction reactions involving electron transfer.

see this page for more details of the full  bond energy calculations

a  fuel cell  is a device to make electricity that functions like an electrical cell or battery that you supply with a fuel (liquid or gas) and an oxidant (oxidising agent, usually oxygen gas) which react together in a redox reaction (oxidation + reduction) to release energy as a flow of electrons i.e. an electrical current capable of doing useful work.

the oxidation of the fuel and the reduction of the oxidant reactions take place on electrodes (see diagram on right, all fully explained further down the page).

fuel cells essentially a device to release the chemical potential energy of combustible fuels as electrical energy  at a much lower temperature and without the flame!

so, the idea of a  hydrogen–oxygen fuel cell  is to release the energy from hydrogen reacting with oxygen, not as heat as in normal combustion in air, but as  useful electrical energy  i.e. a practical electricity supply.

hydrogen-oxygen fuel cells are much efficient than conventional power stations or batteries (e.g. zinc-carbon) because the electrical energy is directly generated from the chemical reaction between the oxidant and the fuel - there are no complications with boilers, turbines and generators.

in fossil fuel power stations, motor vehicles, coal/gas fires etc. quite a percentage of energy is lost as waste heat.

with a fuel cell there are fewer stages in producing the useful energy, so there is less opportunity to lose potentially useful energy e.g. waste heat, friction from moving parts etc.

a hydrogen–oxygen fuel cell is a non–polluting clean fuel since the only combustion product is water.

fuel cells  do not produce pollutants like carbon monoxide, sulfur dioxide and nitrogen oxides - gases you get from fossil fuel combustion in power stations or burnt road vehicles..

cars powered by fuel cells would be quite an environmental advantage in cities, where electric cars are already beginning to be significantly used in developed countries.

fuel cells could replace larger batteries which are not easily recycled and contain highly toxic metal compounds.

it would be an ideal fuel on this basis e.g. for motor vehicles, but that's not the only factor to consider!

it would be ideal if the hydrogen fuel could be manufactured by electrolysis of water e.g. using solar cells.

hydrogen can be used to power fuel cells.

it all sounds wonderful but, still technological problems to solve for large scale manufacture and distribution of 'clean' hydrogen gas or use in generating electricity and its rather an inflammable explosive gas!

explanation:

fuel cells e.g. the hydrogen-oxygen fuel electrical cell

fuel cells have to be supplied by an external source of fuel (e.g. hydrogen) and an oxidant e.g. oxygen or air.

the hydrogen or any other fuel is oxidised electrochemically inside the fuel cell to produce a potential difference i.e. a voltage capable of producing a working current.

the overall chemical reaction in a hydrogen fuel electrochemical cell involves the oxidation of hydrogen by oxygen to produce only water.

hydrogen fuel cells offer an alternative to rechargeable cells and batteries.

a fuel cell will produce a potential difference  ('voltage')  and a workable electric current until one of the reactants is used up.

hydrogen gas can be used as fuel.

it burns with a pale blue flame in air reacting with oxygen to be oxidised to form water.

hydrogen + oxygen  ==>   water

2h2(g)  + o2(g)  ==>   2h2o(l) 

one negative thing it that it can kill water animals. another negative thing is it can cause the destruction of ecosystem. one way water pollution can be reduced is to conserve energy.