• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Comparing the enthalpy of combustion of various alcohols.

Extracts from this document...

Introduction

Comparing the enthalpy of combustion of various alcohols Aim My aim is to find out the energy changes of combusting alcohols. (Methanol, Ethanol, Propanol and Butanol) Background Info Key science Chemistry by Eileen Ramsden says that "an alcohol is a series of organic, homologous compounds, with the general formula CnH2n+1OH." Each member of the series has the O-H group in its molecule. As you go up the homologous series of the alcohols, their physical properties start to vary but their chemical properties remain the same. Alcohols react with the oxygen in the air to form the products water and carbon dioxide: Methanol = CH3OH +1.5O2 CO2 + 2H2O Ethanol = C2H5OH +3O2 2CO2 +3H2O Propanol = C3H7OH +4.5O2 3CO2 +4H2O Butanol = C4H9OH +6O2 4CO2 + 5H2O This is an example of combustion. "Reactions of this kind, which give out energy are exothermic reactions (ex = out; therm = heat)." (Key science Chemistry by Eileen Ramsden). Another example of an exothermic reaction is neutralisation. The amount of energy produced by such exothermic reactions can be calculated by using the formula Mass of the substance x rise in temp x specific heat capacity. The specific heat capacity is the number of joules required to heat one gram of water by 1�C. ...read more.

Middle

10 3 90s 18 86 Methanol 50 50 30s 18 31 Methanol 50 50 60s 18 41 Methanol 50 50 90s 16 57 Methanol 100 100 30s 18 21 Methanol 100 100 60s 18 27 Methanol 100 100 90s 18 34 Method The apparatus is set up as shown above. The apparatus will be placed in a card box over a heat proof mat. This is to minimise the amount of heat lost to the environment. Firstly, I will fill a beaker of water containing 50cm, measuring it out using a measuring cylinder. Then, I will measure the temperature of the water. This will give me the start temperature. After that I will weigh a spirit burner containing an alcohol with its lid. This will give me the starting mass of the spirit burner. Having done this, I will clamp the beaker so the bottom is about 5 cm above the wick of the spirit burner. Then I will light the spirit burner and the stir the water with the thermometer. I will allow the spirit burner to burn for 1 minute. After that, I will reweigh the spirit burner with the lid, which will allow me to work out the change in mass. ...read more.

Conclusion

I can see that it takes more energy to break up the bonds of butanol (+7507 mol) in comparison to methanol (+2803 mol). This is also evident from the data book value. This is also evident from the data book values which I stated in my Bond energy calculation section. There is a pattern and a numerical trend from these data suggesting that as you go up the homologous series the more exothermic the reaction will become. This is because there are more carbons present in alcohols high in the homologous series. Therefore I predict that Butanol will be the most exothermic because it has the greatest mass per mole of the four alcohols provided; therefore it will produce the most heat in a given time. As a result I predict the alcohol with the greatest relative molecular mass will be the most exothermic and Methanol with the least relative molecular mass will be the least exothermic. I think that the order of the alcohols (highest heat produced to lowest heat produced) will be: butanol, propanol, ethanol and methanol. Safety I will also need to ensure that I conduct the experiments safely. As alcohols are very dangerous and highly flammable I will wear my safety goggles at all times. I will need to keep all lose items off. The lids on the alcohol must be kept on at all times to prevent evaporation or any spillage. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Organic Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Organic Chemistry essays

  1. The Combustion of Alcohols and the factors affecting these reactions

    Although I have two anomalies in two separate alcohols which means I only have two valid results for the alcohols Ethanol (1.71g change) and Methanol (0.78g change). These may have occurred as there were many possible chances for error in the equipment, such as evaporation of the alcohols before weighing them.

  2. Investigating the Combustion of Alcohols

    + (12�1) + 16 = 88 g Number of moles of pentan-1-ol burned = mass burned mass of 1 mol =0.61g = 0.0069 mol 88 Enthalpy Change of Combustion of = Energy transferred Pentan-1-ol ?HC Number of moles = -7875 J 0.0069 mol = -1136065.574J = -1136065.574J / 1000 =

  1. Comparing the enthalpy changes of combustion of different alcohols.

    I am keeping the variables that I do not wish to change as constant as I can; although some of these are hard to control e.g. amount of O2 present in the atmosphere. The plan that I have used will provide reliable results as I plan to repeat the experiment three times.

  2. Investigate the enthalpy change of different alcohol

    Energy transferred (J) 1st trial 18 -0.73 15012 2nd trail 20 -0.71 16680 3rd trial 21 -0.72 17514 Average 19.67 -0.72 16402 E.g. for the 1st trial: Energy transferred = 18C x 200g x 4.17J/C/g = 15012J Now I want to find out the enthalpy change of energy that would be transferred to

  1. Comparing the Enthalpy changes of Combustion of different Alcohols.

    = 1381117.5J (1.d.p.) * Enthalpy Change of Combustion: (138111.7J/1000) = (1.d.p.) = -1381.1Kjmol-1 Butan-1-ol * Mass of water used: 189.7g * Temperature rise in water: 20oC * Mass of fuel used: 1.6g * To work out the amount of heat absorbed by the water in the experiment we do the following: (mass of water)

  2. Comparing the heat energy produced by combustion of various alcohols

    In this experiment, I only change the alcohols, so I can make this experiment be a fair test. Testing I'm going to do a quick test, because I want to know what is the happening about the experiment. First, I put 100ml (not accurately)

  1. Comparing the enthalpy changes of combustion of different alcohols

    and 6 bonds are made (4 O-H bonds and 2 O-C bonds). Oxygen breaks 4 bonds and makes 6 bonds, because this is a combustion reaction, the oxygen needs to be fully combusted, and it is the oxygen bonds being made that give out the most energy when bonds are being formed.

  2. Molar Heat of Combustion of Alcohols

    We can use the formula to work out how much 1 mole of the alcohol would give out by adding up all of the atomic masses in the compound and then multiplying that by the energy given out by 1g of the alcohol.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work