Comparing the enthalpy changes of combustion of different alcohols
Oliver White - Comparing the enthalpy changes of combustion of different alcohols. Theory When chemical reactions occur, bonds between atoms are broken and new bonds are made. The amount of energy needed to break a particular bond is called its bond enthalpy(H). We cannot measure the enthalpy of a substance but we can measure the change in enthalpy(?H) when a reaction occurs. ?H = Hproducts - Hreactants Hproducts is the final enthalpy of the system, measured in joules. In a chemical reaction, Hproducts is the enthalpy of the products. Hreactants is the initial enthalpy of the system, measured in joules. In a chemical reaction, Hreactants is the enthalpy of the reactants. Enthalpy change in a chemical reaction gives the gives the quantity of energy transferred to or from the surroundings, when the reaction is carried out openly. In an exothermic reaction, the enthalpy of the reacting system decreases. ?H is negative. In an endothermic reaction, the enthalpy of the reacting systems increases. ?H is positive. When chemists talk about enthalpy changes they often refer to the system meaning the reactants and the products of the reaction they are interested in. The system can lose or gain enthalpy depending on the surroundings meaning the rest of the world: the test tube, the air etc. I will be investigating the enthalpy change of combustion of different alcohols. The
Comparing the enthalpy changes of combustion of different alcohols.
COMPARING THE ENTHALPY CHANGES OF COMBUSTION OF DIFFERENT ALCOHOLS Analysis Results Table Alcohol Initial Temperature (c) Final Temperature (c) Initial Mass (g) Final Mass (g) Methanol 20 35 88.36 86.40 Ethanol 20 35 233.92 232.31 Propan-1-ol 20 35 244.67 243.24 Butan-1-ol 20 35 213.54 212.29 Pentan-1-ol 20 35 95.44 94.46 Hexonal 20 35 217.38 216.66 Alcohol Mass Loss (g) Relative Formula Mass Number of Carbon Atoms Methanol .96 32 Ethanol .61 46 2 Propan-1-ol .43 60 3 Butan-1-ol .25 74 4 Pentan-1-ol 0.98 88 5 Hexonal 0.72 02 6 Calculations The first step I need to take in calculating the amount of heat absorbed by the water in each experiment is to find out how much energy is transferred to the water to raise its temperature. This can be calculated using the formula: Mass of water (x) Rise in temp (x) Specific heat capacity Energy transferred to water = 200 x 15 x 4.2 = 12600 J I now need to calculate the number of moles in each alcohol so that I can find out the enthalpy change of combustion for the alcohols using this formula: Enthalpy = Energy transferred to water (/) Moles of fuel burnt To do this I will use the formula: Number of moles = Mass Burnt (/) Relative molecular mass Example of Complete Alcohol Calculation Eg. Methanol Enthalpy Change of Combustion = Energy transferred to water /
Comparing the enthalpy changes of combustion of different alcohols.
Rebecca Winter November 2003 Plan Comparing the enthalpy changes of combustion of different alcohols I am going to investigate the enthalpy change of combustion of a number of alcohols. The enthalpy change of combustion of a fuel is a measure of the energy transferred when one mole of fuel burns completely under the stated conditions. Enthalpy is defined as the energy of reaction, or the heat energy associated with a chemical change. I will be investigating how and why the enthalpy change is affected by the molecular structure of the alcohol. Therefore, I will attempt to find how the number of carbon atoms that the alcohol contains affects the enthalpy change that occurs during the combustion of the alcohol. Alcohols are derived from alkanes by substituting an -OH group for an -H atom. They are a series of related organic molecules and have a general formula of: CnH2n+1OH, where 'n' is the number of carbon atoms present. Alcohols have physically and chemically similar properties due to the similarities in molecular structure, and the fact that they differ only in the length and structure of the hydrocarbon chain. In my investigation I will be dealing with the first five alcohols in the homologous series; Methanol, Ethanol, Propan-1-ol, Butan-1-ol and pentan-1-ol. I have chosen five alcohols as I feel that it is a suitable range that I
Comparing the enthalpy changes of combustion of different alcohols
Comparing the enthalpy changes of combustion of different alcohols Planning Introduction In this assessment I will be comparing the enthalpy change of combustion of different alcohols, to investigate if enthalpy change is affected by the molecular structure of an alcohol. The standard enthalpy of combustion is the enthalpy change when one mole of a substance burns completely with oxygen under standard state. I will use different alcohols as a means of comparing the molecular structure. The different alcohols I will be using are: Methanol, Ethanol, Propan-1-ol, Propan-2-ol and Butan-1-ol. I chose these alcohols as they each change in structure by one extra carbon atom, (except Propan-2-ol, which is similar to Propan-1-ol, but has its hydroxyl group attached carbon 2 instead of carbon 1) allowing me to have a variety of different examples to compare. I will be measuring the amount of energy transferred from the fuel to the water. I know that it takes 4.2 Joules of energy to raise 1 gram of water by 1 C. This can be shown in the equation 'energy transferred = mass of water x temperature change x 4.2'. Once I have the energy transferred, I will use the formula 'moles = mass/molecular mass' to find out the energy transferred per mole. The independent variable for my experiment is: * The type of alcohol used (Methanol, Ethanol, Propan-1-ol, Propan-2-ol and Butan-1-ol). The
Comparing the enthalpy changes of combustion of different alcohols
Comparing the enthalpy changes of combustion of different alcohols Altaf Korimbocus Aim I am going to investigate the difference in enthalpy of combustion for a number of alcohols, the enthalpy of combustion being the 'enthalpy change when one mole of any substance is completely burnt in oxygen under the stated conditions'. I plan to find out which alcohol, out of methanol, ethanol, propanol and butanol, produces the most energy when burned in air Background and other information Methanol is the smallest alcohol, it releases 524.5 kJ mol-1, the next largest, Ethanol is one carbon and two hydrogen's larger, It release 1013 kJ mol-1 this is a difference of 488.5 kJ mol-1 this trend continues as the alcohols get larger. This is effectively because the only difference between the alcohols is a increase in size by one carbon and two hydrogen's each time. For my investigation I am going to use propan-1-ol and butan-1-ol as representatives of propanol and butanol. Propanol and butanol are large enough molecules to form isomers etc, I have decided to use propan-1-ol and butan-1-ol because they have the closest structural arrangement to the other alcohols that I am going to be testing. Using butan-1-ol and propan-1-ol means all the alcohols that I am comparing have their OH group joined onto an end carbon and they are all straight chain alcohols. I have chosen the four alcohols
Analysis Of Commercial Vitamin C Tablets
Experiment 5 Date: 18-10-2005 Analysis Of Commercial Vitamin C Tablets Objective To determine the mass of Vitamin C in 1 pill of Vitamin C tablet. Introduction In this experiment, the concentration of sodium thiosulphate solution is not given. So, we need to standardize it through titration. Sodium thiosulphate reacts with iodine in the following reaction: I2 + 2S2O32- ----------------->2I- + S4O62- After an amount of S2O32- is added, the solution of I2 turns pale yellow. When starch solution is added and more S2O32- is added, the solution reaches its end point, which is colorless. In this way, the molarity of the thiosulphate solution is determined. Vitamin C could be oxidized by iodine in the presence of acid in the following equation: Due to the low solubility of iodine, direct titration of iodine solution and Vitamin C is unsuitable. Then how could the experiment be done? The experiment could be done by adding acidified Vitamin C solution into potassium iodide solution. Then, we add potassium iodate to allow the following reaction to take place: IO3- + 5I- + 6H+ ----------------> 3I2 + 3H2O I2 formed in this reaction could react with the Vitamin C in as mentioned in the above equation. The I2 not yet reacted would then be titrated against thiosulphate solution, like the first equation, to determine its amount. This method is a kind of back titration. It is
Enthalpy changes
Enthalpy Changes Analysis Results Recording Test 1 Test 2 Test 3 Units Mass of CaCO3 + weighing bottle 3.50 3.52 3.50 g Mass of empty weighing bottle .04 .01 .00 g Mass of CaCO3 used 2.50 2.50 2.50 g Temperature of acid initially 21.50 22.00 21.00 °C Temperature of solution after mixing 24.00 24.00 23.00 °C Temperature change during reaction 2.50 2.00 2.00 °C Mass of CaO + weighing bottle 2.52 2.30 2.40 g Mass of empty weighing bottle .12 0.90 .00 g Mass of CaO used .40 .40 .40 g Temperature of acid initially 22.00 22.50 21.00 °C Temperature of solution after mixing 32.50 32.50 30.00 °C Temperature change during reaction 0.50 0.00 9.00 °C ?H1 The Reaction between CaCO3 + HCL J = m.c. ?T is used to calculate the energy produced using heat capacity of HCL, and 50ml of HCL with the temperature change in the reaction. J = m.c. ?T 50 x 4.2 x 2.5 = -525 J 50 x 4.2 x 2 = -420 J 50 x 4.2 x 2 = -420 J AVG = -455 J moles = mass 2.5 = 0.025 molar mass 100 ?H1 = -18.22 units = kJ/mol ?H2 The Reaction between CaO + HCL J = m.c. ?T is used to calculate the energy produced using heat capacity of HCL, and 50ml of HCL with the temperature change in the reaction. J = m.c. ?T 50 x 4.2 x 10.5 = -2205 J 50 x 4.2 x 10 = -2100 J 50 x 4.2 x 9 = -1890 J AVG
Investigate the enthalpy values for the reaction between calcium carbonate and calcium oxide with Hydrogen Chloride.
Investigate the enthalpy values for the reaction between calcium carbonate and calcium oxide with Hydrogen Chloride. Chemistry coursework Aim I will carry out this practical to investigate the enthalpy values for the reaction between calcium carbonate and calcium oxide with Hydrogen Chloride. I will collect the results and analyse them to reach a conclusion about the reactions between the reactants. Theory I will measure the temperature changes when calcium oxide and calcium carbonate react with hydrochloric acid solution. I can use a Hess' Law cycle to calculate the enthalpy changes using the equation. Enthalpy change = mass of liquid x temperature change x specific heat capacity This equation will help me to calculate the enthalpy changes, and which reaction was more exothermic, and why. I drew a Hess' Law cycle to illustrate the enthalpy values. CaCO³ (s) CaO (s) + CO² (g) H¹ H² H³ CaCl² (aq) Fair test · We used scales correct to 2 decimal places. · We measured the calcium oxide and calcium carbonate straight into the beaker to avoid leaving particles on the paper I would otherwise have measured it on. · We measured the hydrochloric acid using a measuring cylinder including the meniscus to make it accurate, and poured out as much as possible. We couldn't wash it out and this would have affected the concentration of the acid and the rate of
Investigation of Some of the Properties of a Pair of Cis-Trans Isomers
Experiment18 Aim To determination the partition coefficient of ethanoic acid between water and butan-2-ol. Procedure . The room temperature was recorded. 2. 15cm3 of the given aqueous ethanoic acid and 15cm3 of butan-2-ol were poured into a 100cm3 separating funnel, using suitable apparatus. The funnel was stoppered and was shook vigorously for 1 to 2 minutes. (The pressure in the funnel was released by occasionally opening the tap.) 3. 10cm3 of each layer was separated approximately. (The fraction near the junction of the two layers was discarded.) 4. 10.0cm3 of the aqueous layer was pipetted into a conical flask and was titrated with 0.1 M sodium hydroxide solution using phenolphthalein. 5. Using another pipette, 10.0 cm3 of the alcohol layer was delivered into a conical flask and was titrated with 0.1 M sodium hydroxide solution. 6. Steps (2) to (5) was repeated with another separating funnel using the following volume: 25cm3 of aqueous ethanoic acid and 15cm3 of butan-2-ol 7. For each experiment, the ratio of the concentration of ethanoic acid in the aqueous layer to that in the butan-2-ol layer was calculated. Result Room temperature: 29? Volume of butan-2-ol: 15 cm3 Volume of 0.2M ethanoic acid / cm3 Volume of 0.1M NaOH titre for aqueous layer / cm3 Volume of 0.1M NaOH titre for alcohol layer / cm3 Partition coefficient K= 5 0.00 2.55 0.796 25
Thermal Decomposition of Copper Carbonate
Thermal Decomposition of Copper Carbonate ( CuCO3) Introduction: Copper Carbonate (CuCO3) decomposes by heat to form either one of two oxides, namely Copper (I) Oxide (Cu2O) and Copper (II) Oxide (CuO). This reaction can be written as two different equations: a. 2CuCO3 (s) --> Cu2O (s) + 2 CO2 (g) + 1/2 O2 (g) b. CuCO3 (s)--> CuO (s) + CO2 (g) Aim: In this experiment we will be required to identify the correct balanced stoichiometric chemical equation for the decomposition of the copper carbonate from the volume of carbon dioxide produced. Background Information: When metals are heated they react with oxygen in the air. As the metal is heated it reacts with the oxygen to form an oxide. Column II carbonates are decomposed by heat to form corresponding oxides and carbon dioxide. The temperature of decomposition depends on the reactivity (in relation to stability) of the metal. In this way, the carbonates of sodium and potassium are stable at the highest temperatures of a Bunsen burner flame whereas the carbonates of silver and copper are easily decomposed. Basic Idea: a. Copper carbonate will be heated b. Decomposition will occur c. A gas will be released and it will be collected. d. The volume of the gas that will be collected will give us an indication as to which equation is correct. Calculations - Hypothesis: (Essential Information) 'At room
