Determining the change in enthalpy for the combustion of Mg using solution calorimetry and heat summation.
Student Name Period 1 C.P. Chem March 7,2003 Determining the change in enthalpy for the combustion of Mg using solution calorimetry and heat summation. Abstract Hess's law of heat summation states that the value of ?H for a reaction is the same whether it occurs directly or as a series of steps. This principle was used to determine the change in enthalpy for a highly exothermic reaction, the combustion of magnesium metal. Enthalpy changes for the reactions of Mg in HCl (aq) and MgO (s) in HCl (aq) were determined experimentally, then added to that for the combustion of hydrogen gas to arrive at a value of -587 kJ/mol Mg. Compared with the accepted value of -601.8 kJ/mol Mg, our experimental error was 2.46%. Introduction In this investigation the change in enthalpy will be determined from the following equation: 2Mg + O2 ? 2MgO, but in an indirect manner. Magnesium metal burns with a bright extremely hot flame to produce magnesium oxide. It would be difficult to measure the heat of the reaction since the reaction is rapid and occurs at a high temperature (LeMay et al, 1996). So, to determine the change in enthalpy we will employ Hess's Law of heat summation: It states that the value of ?H for a reaction is the same whether it occurs directly or as a series of steps (LeMay et al, 1996). We will perform the two following reactions: Mg + 2HCl ? MgCl2 + H2 and MgO
Electrochemistry - Redox reaction.
INTRODUCTION One reactant is oxidized and another reactant is reduced, this chemical reaction is called Redox reaction. Redox reactions involve in generation of electricity in electrochemical cells. [1] Two different solid metals in solution of their ions made up of electrochemical cell, which are connected by a salt bridge or a wire. Each metal is an electrode, which will either be oxidized or reduced in a half-cell. [2] The pairs of species, e.g. Zn2+(a.q)/Zn(s) and Cu2+(a.q)/Cu(s), etc. are known as redox couple. The relative oxidizing or reducing strengths of redox couples are expressed in terms of their standard electrode potentials, EO, which have the units of Volts.[3] A general cell diagram for an electrochemical cell is shown below: fig 1 [2] The standard potential of the cell, EO=EOR-EOL where EOR =the EO of the right-hand-side electrode and EOL= the EO of the left-hand-side electrode.[4] Aim of the experiment was to understand how electricity worked to form a simple circuit. This experiment had three sub-experiments. First was to build a simple circuit. Second was to make an electrochemical cell. At last was to make battery with lemon, electrodes. METHOD EXPERIMENT I. A circuit was set up as in the diagram below: After setting up the circuit, the switch was closed and observation was recorded. EXPERIMENT II. The apparatus was set up as the
Chemistry AS4 Course Work
AS4 Finding and enthalpy change using Hess's Law Results Experiment 1: Mass of weighing bottle and potassium hydrogen carbonate: 25.75g Mass of weighing bottle: 18.75g Mass of potassium hydrogen carbonate: 4.00g Time(min) 0.0 0.5 .0 .5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 Temperature(C) 25.0 25.0 25.0 25.0 25.0 25.0 25.0 5.0 4.0 4.0 4.0 4.0 4.0 4.0 Potassium hydrogen carbonate and hydrochloric acid: KHCO3(S) + HCl (aq) KCl (aq) + H2O (l) + CO2 (g) Fall in temperature for complete reaction: 25-14=11 = 11C, Mass= 30g, C= 4.18Jg-1K-1 H1= MxCx T =30x4.18x (+11) = 1379.4J/1000 = 1.3794J Number of moles of acid = (30/100) x2 = 0.06 moles in excess Molar mass of potassium hydrogen carbonate Mr= 39.1+1.0+12.0+48 = 100g mol-1 Number of moles= m/Mr = 4/100 = 0.04 mol H for 1 mole= 1.3794KJ/0.04 = 34.49KJmol-1 Experiment 2: Mass of weighing bottle and magnesium carbonate: 20.75g Mass of weighing bottle: 8.75g Mass of magnesium carbonate: 2.00g Time(min) 0.0 0.5 .0 .5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 Temperature(C) 26.5 24.5 24.5 24.5 24.5 24.5 24.5 30.0 30.0 30.0 29.5 29.5 29.5 29.5 Magnesium carbonate and hydrochloric acid: MgCO3(S) + 2 HCl (aq) MgCl2 (aq) +H2O (l) + CO2 (g) Rise in temperature for complete reaction: 24.5-30.0= (-5.5C) H= -5.5C,
EN4 Determination of Enthalpy Change of Combustion
) Title: EN4 Determination of Enthalpy Change of Combustion 2) Aim/Objective: To find out the calibration factor of propan-1-ol by burning a measured mass of it in a spirit lamp and use the calibration factor to find out the enthalpy change of combustion of other alcohols (ethanol, butan-1-ol, pentan-1-ol, hexan-1-ol). 3) Results: (1) Calibration of the Calorimeter Molar mass of propan-1-ol 60 Initial mass of spirit lamp + propan-1-ol (m1) 262.63 g Final mass of spirit lamp + propan-1-ol (m2) 261.53 g Mass of propan-1-ol burnt (m1-m2) .1 g Number of moles of propan-1-ol burnt (n) 0.01833 mol Initial temperature of calorimeter 7.8? Final temperature of calorimeter 37.8? Temperature raised (?T) 20? Standard enthalpy change of combustion of propan-1-ol ?HC [propan-1-ol (l)] * n -2017kJ/mol Heat energy released during the experiment, E = ?HC [propan-1-ol (l)] * n 36.978kJ Heat energy required for the calorimeter to rise 1 K = E/?T = C (Calibration factor) .849kJ/mol (2) Experimental data of other alcohols Ethanol Butan-1-ol Pentan-1-ol Hexan-1-ol Molar mass 46 74 88 02 Initial mass of spirit lamp + alcohol (g) 287.53 276.04 274.04 218.79 Final mass of spirit lamp + alcohol (g) 286.28 274.30 273.10 217.88 Mass of alcohol burnt (g) .25 .74 0.94 0.91 Number if mole of alcohol burnt (n) 0.0272 0.0235 0.0107 0.00901
Vitamin C. I will investigate whether orange juice contains the most Vitamin C and how I can speed up and slow down the oxidation process of Ascorbic Acid.
Vitamin C in Fruit Juices Background: Ascorbic Acid, or more commonly known as Vitamin C, is a monosaccharide that has a five-membraned unsaturated ring with two hydroxyl groups attached to doubly bonded carbons. This feature means that Ascorbic Acid is readily oxidised to dehydroascorbic acid. This reaction is called oxidation because the Ascorbic Acid is loosing electrons. Ascorbic Acid deficiency leads to scurvy, a disease that shows weakness, small hemorrhages throughout the body that cause gums and skin to bleed, and loosening of the teeth. Vitamin C is a water soluble antioxidant, and plays a vital role in protecting the body. The body absorbs extra vitamin C in response to an infection. Because it is a water soluble vitamin, any unused vitamin C is excreted. The minimum daily requirement is 30 mg; the recommended daily allowance is 60-70 mg. C6H8O6 + C12H7NCl2O2 ----------> C6H6O6 + C12H9NCl2O2 The electrons lost from Ascorbic acid will be used to reduce one of my indicators Dichlorophenolindophenol(DCPIP), to DCPIPH and then to DCPIPH2. DCPIP (blue) + H+ ----------> DCPIPH (pink) DCPIPH (pink) + Vit C ----------> DCPIPH2 (colorless) However I will also be using Iodine as an indicator to see if it is a better one than DCPIP. DCPIP oxidises very easily and therefore it will take more DCPIP to oxidise vitamin C because it is already oxidizing. DCPIP is an oxidizing
Design two experiments, one using titration and one using gas collection to show that H2SO4 is a dibasic acid.
Chemistry Practical Write-Up Aim: Design two experiments, one using titration and one using gas collection to show that H2SO4 is a dibasic acid. Gas Collection Experiment Prediction: If H2SO4 is dibasic it should give off a volume of hydrogen molecules, equal to the volume of H2SO4 used, below I have calculated how much gas to expect: H2SO4 + Mg › MgSO4 + H2 H2SO4 Concentration: 1 Mol/dm3 Volume: 0.025dm3 Moles: 1x0.025 = 0.025 H2 Moles: 0.025 0.025 * 24 Volume: 0.6dm3 Apparatus: Conical Flask, Magnesium, H2SO4, Bung, delivery tube, bowl of water, measuring cylinder. Diagram: Method: * Setup Apparatus as shown in the diagram. * Fill a conical flash with 25cm3 H2SO4. * Fill the measuring cylinder with water, making sure there are no bubbles, and turn it upside down in the water bath. * Drop the magnesium into the conical flask, and place the quickly place the bung on top. * The hydrogen gas will begin to displace the water in the measuring cylinder, wait until this stops, and record the results in a table like shown below, repeat until you have 3 results and calculate the average amount of gas evolved. Gas(dm3) - 1 Gas(dm3) - 2 Gas(dm³) - 3 Gas Average(dm³) To keep the results accurate we will keep all equipment and solutions used the same every time, we will do this experiment 3 times and take the average of the readings, and use this to see if
Experiment to determine the order of the reaction of Iodine with Acetone by using titration method.
Experiment No.: 11 Title: Investigation of the Order of the Reaction of Iodine with Acetone Aim: To determine the order of the reaction of Iodine with Acetone by using titration method. Introduction: Chemical kinetics is the investigation of the rates at which chemical reactions occur, it is very important as it enables the exploration of reaction mechanism. Even the simplest chemical may consist of a complex sequence of events. Thus, it is customary practice to simplify matters by devising experiment in which, effectively, the concentration of one species only is changing. In this experiment, reactants of different volumes are given, iodine stored in KI(aq) solution is first mixed with given volume of sulphuric acid, acetone and distilled water into a flask. Students are to be worked in pairs. Our group carried out experiment 2 (20cm3 of Acetone) and only experiment 1, 2 and 3 were underwent in our class. Group(Experiment): 2 3 4 5 Flask A: Volume of I2 solution(aq)/cm3 50.0 50.0 50.0 50.0 50.0 Flask B: Volume of H2SO4 soln/cm3 25.0 25.0 25.0 25.0 25.0 Volume of Acetone soln/cm3 25.0 20.0 5.0 2.5 6.25 Volume of distilled H2O/cm3 0 5.0 0.0 2.5 8.75 The flask of mixture is placed in a thermostat. At a fix time interval, portions of mixture are added to a flask containing NaHCO3 solution. Since iodine reacted with acetone to give I- ions,
The aim of this experiment is to produce Aspirin. This is an estrification in which an alcohol reacts with an acid and a small molecule is often eliminated. The reaction takes place under a concentrated acid catalyst which speeds up the chemical reaction.
Contents Planning Page number * Background Information---------------------------------------- 3 * Aim---------------------------------------------------------------- 4 * Plan - (choices of equipment)--------------------------------- 5 - 15 - (risk assessment) * Synoptic grid----------------------------------------------------- 16 Implementing * Preparation of Aspirin------------------------------------------ 18 - 19 * Melting point determination---------------------------------- 20 * Forward titration------------------------------------------------ 21 - 24 * Back titration---------------------------------------------------- 25 - 28 Analysing * Calculations----------------------------------------------------- 30 - 35 * Conclusion------------------------------------------------------ 36 - 37 Evaluating * Uncertainty associated with measurements--------------- 39 - 46 * Limitations of methods-------------------------------------- 47 * References---------------------------------------------------- 49 Background Information Introduction (1) (2) Aspirin is member of a family of chemicals called salicylates. Aspirin the pain reliever also known by the chemical
Experiment to Compare the Enthalpy Changes of Combustion of Different Alcohols
Experiment to Compare the Enthalpy Changes of Combustion of Different Alcohols Introduction: This plan will try to outline how the experiment of comparing changes of combustion of different alcohols will be conducted and what results are expected. Background When chemical reactions take place they are often accompanied by energy changes. Chemical reactions most frequently occur in open vessels. That is, they take place at constant pressure. Enthalpy refers to energy at constant pressure (volume may vary). Enthalpy: An example is best to illustrate to show enthalpy works. Methane - how much energy does its molecules contain? The first thing needed is the amount of methane present = 1 mole (16 g). What ever its value, the total amount of energy in a given amount of a substance (sometimes called the Heat energy content) is known as the enthalpy, denoted H. Methane is a fuel to get energy from it, react it with oxygen. CH4(g) + 2O2(g) ? CO2(g) + 2H2O(l) The above chemical equation shows that 2 moles (64 g) of oxygen molecules are required to burn 1 mole of methane. Again, it is impossible to know the total enthalpy (heat energy content) of the oxygen. Likewise, we can't know the total heat energy content of 1 mole of CO2 and 2 moles of H2O (the products). Enthalpy Change ?H = (HCO2 + 2HH2O) - (HCH4 + 2HO2) In general, ?H = ?Hproducts - ?Hreactants But
Preperation of Antifebrin
Preparation of Antifebrin In this experiment, I am going to prepare the organic compound of antifebrin from readily available chemical reagents. Antifebrin is an odourless solid chemical of white flake-like appearance. Chemically, antifebrin is the amide phenylethanamide CH3ONHC6H5. It's slightly soluble in water. It does have the ability to self-ignite if it reaches the temperatures of 545°c but otherwise it's a stable compound. The pure crystals of antifebrin are plate shaped and white in colour. The antifebrin in this experiment is prepared from the reaction between phenylammonium chloride (C6H5NH3Cl) and ethanoic anhydride[ (CH3CO)2O ]. Chemical Equation for the Reaction: C6H5NH3+ Cl- + (CH3CO)2O CH3ONHC6H5 + CH3OOH + HCl Procedure & Observations: Procedure Observation Dissolve 1.0g of phenylammonium chloride in 30cm3 of water in a conical flask. Phenylammonium chloride is a greyish-green crystal like product. Adding water to it gives a solution pale grey with green tinge. After dissolving the solutions turns clear with a green-grey colour and no precipitate. Prepare a solution of 6.0g of sodium ethanoate in 25cm3 of water in a conical flask. Sodium ethanoate is a white powder. It dissolves completely in water to give a colourless solution. Carefully add 2cm3 of ethanoic anhydride to the solution of phenylammonium
