Question

pre lab- heat of combustion (1-3D)

Experiment 10 HEAT OF COMBUSTION Pre-Lab 1. The Law of Conservation of Energy can be applied to combustion processes where fuel + oxygen products + energy The total chemical energy associated with the reactants must be the same as the total chemical energy of the products when the heat of combustion is included. a) Underline the graph which best represents the relationship between the stored chemical energy of the reactants and products in a combustion process Energy Energy Reactants Products Reactants Products b) The difference in length of the bars on the correctly chosen graph represents the heat of combustion. Show this by using a vertical arrow on the graph. c) The following represent the combustion of one mole of the potential fuels methane (CH) and methanol (CH,OH). They form a common set of products. CH4 () + 2O2(g) →CO2() + 2 H2O) + 803 kilojoules CH,OH() + 3/2 0, 002) + 2 H20 (8) + 639 kilojoules Circle the reaction where the reactants have a larger chemical potential energy. Does the presence of the oxygen atom and its chemical bonds (C-O,O-H) increase or decrease the chemical potential energy of methanol compared to methane (C-H)? increase decrease

Answer 1

Energy liberated as heat of Combustion, Reactants products 2-) In Combustion processes stored Chemical Energy of Reactants is greater than stored Chemical Energy of Products. (=) Some Energy is Liberated in the form of Heat & light during combustion process. Greater Amount of Energy will be liberated during Combustion when difference in Energy of Reactants 8 Products is greater. A since we have same products. That means energy of Products is same in both cases. of Reactants Energy is different and since greater amount of Energy is Literated during combustion of one mole of Chu ise 80 3KJ. Thus methane will have larger Chemical potential Energy. (1) n-C-H , n-c-o-n. ( Bond dissociation is Energy Consuming process 8 Bond making is Energy releasing process. =) on the product side of Both reactions equal number of Bonds are formed but on the reactant side unequal number of Bonds and with different Bond energy undergo Dissociat • In CH₂OH The O-H Bond 8 c-o Bond are relatively strong and thus require greater Bond Dissociation energy at the Cost of H stored potential energy.

114.29 = mac X AT (2) Ca Hip & + 25/029 8 CO₂ g + 9 H₂O +5074 ks saat - one role of Ca H 12 = 114.29 114.2g of octane produce energy = 5070 kJ Ig of octane produce energy = 5074 kJ Fuel vame of Octane. = 144 .43 kJ/g) (3) Heat Energy Absorbed by the flask is given an me mass of flank. ca specific heat capacity 9 = 118.5gX0.857 I 18 dx 108 Atz Temperature Change 1015.545 5 (6) Heat Energy Assorted by the water. =) gemac & AT me 192029 ca 4.10 T 1 god - 9 2192.28 x4, 185 18°2x108 ATe lo c. 8033.965 (C) Total Energy = 1015.545] + 8033.965 9049.505 I Energy in kilojoules a gouge505 49.049505 kJ Вели. 1KT I, oo от (d) Each gram of Methand produces energy = 19.9kI i mass of Riethanol which will Produce 9.049505 kJ 10.usug of Methamed E 1.04950s = 10.454g I will produce energy-gourt 19.0 LODO