logo

Standard Enthalpy of Combustion of Ethanol

   

Added on  2021-04-24

6 Pages1084 Words102 Views
SECTION ASolution Q1ai) standard enthalpy of combustion of ethanolii) b) C2H5OH + 3O2 => 2CO2 + 3H2O∆H0combustion = ∑∆H0(reactant bonds) - ∑∆H0(product bonds)∆H0 = [5∆H0C-H + ∆H0C-C + ∆H0C-O + ∆H0O-H] – [4∆H0C = O + 6∆H0O-H]∆H0combustion = [5*413 + 347 + 336 + 464] – [4*805 + 6*464] ∆H0combustion = 3212 – 6004 = -2792 kJ/molThe experimental combustion enthalpy change is lower than the standard enthalpy of combustiondue to heat being lost to the surrounding environment, the metal equipment used absorbs heat, or either inaccurate measurements may also results to lower enthalpy of combustionc) C6H12O6 => C2H5OHC6H12O6 + 6O2 => 6CO2 + 6H2O ....(i)C2H5OH + 3O2 => 2CO2 + 3H2O ....(ii)C6H12O6 => 2C2H5OH + 2CO2

(i)=> 2* (ii)C6H12O6 => 2C2H5OH + 2CO2∆H=∆H1 - 2∆H2 = -2808 – 2(-1368) = -2808 + 2736 = -72 kJ/molQ2) Q2a) the production of sugar for fuel releases much of carbon dioxide into the atmosphere, since when the fuel burns it releases into the atmosphere just the amount of carbon dioxide that the sugar plant took to make the sugar in the first place, as compared to the production of oil for fuelCombustion for sugar for fuel C12H22O11 + 12O2 => 12CO2 + 11H2Oii) The production of sugar for food has same production of carbon dioxide to the atmosphere as producing sugar for fuel, since the carbon dioxide intake and output remain balance.b) Harvesting by hand does not involve fuel engine that burn to produce carbon dioxide, hence it will effectively and efficiently reduce extra carbon dioxide emission to the atmosphere. c) CH3CH2OH + 3O2 => 2CO2 + 3H2Ofor 1 mole of ethanol we obtain 2 mole of CO21 tonne = 1000000 gMole = 100000046=21739.130435molesUsing mole ratio of 1 : 2Mole of CO2 = 2 (21739.130435moles¿ = 43478.26087 molesMass = moles * molar mass = 43478.26087 * 44

= 1913043.4783 g = 1913043.47831000000 = 1.9130 tonnes Q3a) is a process of combining or mixing a substance with oxygenOxygenate hydrocarbons has less energy content because during combustion process the oxygen in the molecule burs first, hence giving off less heat or enthalpy b) This is due to insufficient or incomplete combustion of fuel Incomplete combustion of diesel 2C12H23 + 47O2 => 24CO + 23H2Oc) Since it is oxygenated this allows its complete combustion to results only in production of carbon dioxide as a product rather than carbon monoxide d) Increase level of carbon monoxide reduces the amount of oxygen carried by haemoglobin around the body in red blood cells, resulting in vital organs such as brain, nervous tissues and heart not to receive enough oxygen to work properly. Similarly, emission of carbon monoxide to the atmosphere reacts with hydroxyl radicals hence reducing their abundance; these further causes an increase to the lifetimes of strong greenhouse gases like methane, therefore carbon monoxide indirectly increase global warming Q4a) oil The fermentation of corn requires energy from the burning fossils fuels, this fossil fuels are majorly classified as coal, natural gas, crude oil, oil was precisely what was being used because the Brazil had discovered its own off-shore reserves of oilb) pure ethanol = 30% less per litre of petrol Price of petrol per litre = $2Price per litre of ethanol = 100−30100∗$2 = $1.4

End of preview

Want to access all the pages? Upload your documents or become a member.

Related Documents
Organic Chemistry Assignment Report
|11
|795
|8

Thermochemical Equation for Combustion of Octane and Bond Enthalpy
|6
|1517
|352

Thermodynamic Solution - PDF
|7
|481
|108

Food as Energy – Fuel for Life: Chemistry Essentials Scenario-Based Problem
|10
|3067
|450