Chem Dcp Ce Essay

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TOPIC: ENTHALPY CHANGES IN A REACTION RESEARCH QUESTION: How does changing the number of carbon atoms present in an alcohol affect its enthalpy of combustion when heating 100cm3 of water over a 10 minute period? AIM: The purpose of this experiment is to determine how changing the numbers of carbon atoms in an alcohol will affect how much it can heat 100cm3 of water. INTRODUCTION: The enthalpy (heat) of combustion is the heat given out when 1 mole of the substance (alcohol) undergoes complete combustion with oxygen at a constant pressure. Combustion is always an exothermic reaction; therefore the ΔH is always negative. (“Heat (enthalpy) of combustion”) QUALITATIVE DATA: 1. All the fuels were a yellowish brown yet transparent colour. 2. Aside methanol, all the other fuels formed soot underneath the milk tins after combustion. 3. The fuels had a very strong scent when exposed by burning or opening the lid of the spirit lamp. QUANTITATIVE DATA: TABLE 1: Table of results showing the initial, final and average changes in mass of the alcohols after 100cm3 of distilled water was heated over a 10-minute period. Alkanol | MASS/g | | Trial 1 | Trial 2 | Average Change in Mass/g(±0.002g) | | Initial Mass/g (±0.001g) | Final Mass/g(±0.001g) | Change in Mass/g(±0.002g) | Initial Mass/g(±0.001g) | Final Mass/g(±0.001g) | Change in Mass/g(±0.002g) | | Methanol (A) | 211.196 | 206.740 | 4.456 | 206.740 | 202.336 | 4.404 | 4.430 | Ethanol (B) | 224.763 | 221.965 | 2.798 | 221.965 | 219.328 | 2.637 | 2.718 | Propanol (C) | 206.376 | 204.541 | 1.835 | 204.541 | 202.691 | 1.850 | 1.843 | But-1-ol (D) | 240.198 | 238.799 | 1.399 | 238.799 | 237.194 | 1.605 | 1.502 | Pentanol (E) | 216.526 | 215.132 | 1.394 | 215.132 | 213.642 | 1.490 | 1.442 | Hexanol (F) | 212.494 | 211.222 | 1.272 | 211.222 | 209.882 | 1.340 | 1.306 | Heptanol (G) | 207.233 |

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