Enthalpy And Calorimetry Essay
explanatory Essay
940 words
Introduction: This lab has to do with enthalpy and calorimetry. Enthalpy is a measure of the amount of energy in a system, which is the part of the universe we are studying. Equation one is used to find enthalpy. (Equation 1) ΔH=E +PV In this equation, ΔH is the change in heat, E is energy, P represents pressure, and V is volume. The change in enthalpy is synonymous with the change in heat. If the change in enthalpy is positive, it is an endothermic reaction. A negative answers means it is an exothermic reaction. Equation two is the equation for the enthalpy of a reaction. (Equation 2) Hrxn= Hproducts - Hreactants Calorimetry is used to measure enthalpy. It measures how much heat is flowing. The equation for calorimetry is equation number …show more content…
In this essay, the author
- Explains that equation one is used to find enthalpy and calorimetry, which measures the amount of energy in a system.
- Explains that h is the change in heat, e is energy, p represents pressure, and v is volume. equation two is for the enthalpy of a reaction.
- Explains that calorimetry is used to measure enthalpy. it measures how much heat is flowing.
- Explains that the initial and final temperatures were found for each trial (table 1). these results were averaged, and equation three was used to determine the grams used.
- Explains how the grams of each salt used in the experiment were divided by the change in temperature recorded. equation 4 was used to determine the price.
- Explains that $0.75, $0.36, and $0.19 were used because they cover the cost of the plastic bag, labor and overhead costs.
- Explains the lab's goal to determine which two salts would be best to make a profitable hot and cold pack.
- Explains that styrofoam cup calorimeters will be used for this lab. each packet must be stored at room temperature, cost less than five dollars, and contain a salt and water.
- Explains that the lab lab requires room temperature water, spoons, digital scale, graduated cylinder, plastic boats, styrofoam cups, and a lab quest temperature probe.
These results were averaged (table two). If the final temperature was less than the initial temperature, it will be used as a cold pack. If it is greater, it will be used as a hot pack. To determine the amount of grams used, equation three was used. (Equation 3) G1/ΔT1 = G2/ΔT2 In this equation, the grams of each salt used in the experiment was divided by the change in temperature recorded in the experiment. This was set equal to the amount of grams you would need to reach 65º C or 0º C divided by the temperature change needed to reach the desired temperature. After the amount of grams needed was determined, the price must be found. Equation 4 was used to determine the price. (Equation 3) $0.75 + $0.36 + $0.19 + (P/500) * G $0.75, $0.36, and $0.19 were used because they cover the cost of the plastic bag, labor, and overhead costs. P represents the price of the salt per five hundred grams provided by the company. G is how many grams are needed to reach the desired temperature. The results can be found in table three. (Table 3) Grams Needed and Cost Name of Compound Grams Needed (g) Cost
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- Enthalpy Essayexplanatory essayTo answer the most obvious question, what is ΔHºrxn·? Well, ΔHºrxn· means the change in enthalpy. To break it down further, enthalpy is the measure of the amount of energy in a system. Every single reaction in the entire universe has a change in enthalpy. Energy is held in each and every single bond that puts together the world we see and live in today. When a reaction takes place and bonds are broken and reconnected, energy has been transferred, and enthalpy tells us how much. It is just about nearly impossible to measure all of the energy that there is out there, but scientists can measure how much energy has been transferred through the system. It would be like trying to measure the volume of the ocean, pretty much impossible, huh? But,
In this essay, the author
- Explains that enthalpy is the measure of the amount of energy in a system.
- Explains that enthalpy was first recorded in 1875 by josiah willard gibbs, who did not directly refer to it as heat/energy in a system.
- Explains that there are two types of hand warmers available: air activated and supersaturated solution. combustion reactions have long been used in human history.
- Explains that enthalpy of combustion is now more than ever being explored. it is useful when comparing different fuels and substances to see which ones release more energy when they are burned.
1213 wordsRead More - Calorimetry Lab Reportexplanatory essayThe purpose of the lab is to understand how to calculate the calorimeter constant by using a calorimeter. This allows us to analyze the heat reaction of different substances. Calorimetry is a word that comes from both Latin and Greek. The prefix “Calor” in Latin signifies heat and the suffix “metry” in Greek means measuring. Therefore the word itself translates to measuring heat. Joseph Black, was the first scientist to recognize the difference between heat and temperature. Energy is always present in chemical and physical changes. The change of energy that occurs when there is a chemical change at constant pressure is called enthalpy. Enthalpy changes , as well as physical and chemical changes, can be measured by a calorimeter. The energy that is released or absorbed by the reaction can be either absorbed or released by the insulating walls of the instrument.
In this essay, the author
- Explains that the lab's purpose is to understand how to calculate the calorimeter constant by using the instrument. calorimetry is a word that comes from both latin and greek.
- Explains that styrofoam cups act as calorimeters due to their insulating properties. since most of the heat that forms is absorbed by the solvent, the temperature can be altered.
- Explains that when the amount of hot water released and cold water absorbed does not coincide, it means the calorimeter is absorbing some of the heat.
- Explains the hess's law, which states that the enthalpy of a reaction is independent of the steps it takes to go from reactant to product.
433 wordsRead More - Investigate the difference in enthalpy of combustion for a number of alcohols Enthalpy 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 will be attempting to find how the number of carbon atoms the alcohol contains effects the enthalpy change that occurs during the combustion of the alcohol. Method I plan to measure the enthalpy change by burning the alcohol, using a spirit burner, I will then use the heat produced during the combustion of the alcohol to heat 100ml of water that will be situated in a copper calorimeter directly above the burning alcohol. The calorimeter is made of copper as copper has a high thermal conduction value, this basically means that it is a good conductor of heat so a lot of the heat the copper receives will be passed on to the water which I am then able to measure.
In this essay, the author
- Explains that they will investigate the difference in enthalpy of combustion for a number of alcohols.
- Explains that they plan to measure the enthalpy change by burning alcohol, using a spirit burner, and then use the heat produced during the combustion of the alcohol to heat 100ml of water.
- Explains that during the experiment, they will take a number of measurements, such as the initial temperature of the water and initial mass of alcohol. they will then burn the alcohol until an increase in temperature has occurred.
- Explains that they will need to repeat their experiment a number of times and take an average so they are sure of an accurate result.
- Explains that the calorimeter is held directly above the spirit burner by a retort stand and clamp, and the mercury thermometer, which is very accurate, will be used to measure the water temperature.
- Predicts that alcohols with a greater number of carbon atoms within the molecule will have higher enthalpy of combustion than those with less. bond breaking requires energy while bond making releases energy.
- Explains the balanced equation for the combustion of methanol. the type and number of bonds within each mole of reactants and products are shown.
- Explains that the total energy required to break the bonds in the reactants is 2807.5 dh/kj mol-1, and the difference between them and products is 524.5
- Explains that the energy released by the alcohol is only an approximation for the combustion of methanol because the bond enthalpies vary slightly from one molecule to another.
- Describes the alcohols that they plan to use in their investigation, including methanol, ethanol and propanol.
- Explains that methanol ch3ho + 1.5o2 (g) co2 + 2h2o (l)3 c__h 413 1,5o=o 497
- Explains that the bond enthalpies worked out above clearly show an increase in the overall energy that is released as the alcohols increased in size.
- Compares the enthalpy of combustion (dhc) of different alcohols.
- Explains that they are going to use propan-1-ol and butan-l as representatives of the two alcohols. they are large enough molecules to form isomers and have the closest structural arrangement.
- Explains that they need to use alcohols with as similar structure as possible, with the only difference being the number of carbon atoms within the molecule.
- Explains that alcohols are flammable, so they need to be handled with care, avoiding spillages, and kept in a suitable container.
- Explains that their experiment is safe as long as it is carried out sensibly taking heed of the general laboratory rules.
- Explains that alcohol initial temperature +/- (oc) finaltemperature (g) methanol 21 43 22 213.18 212.06 1.1221
- Explains that the bottom of the calorimeter had a black sooty type substance on it, which was affecting their results for butan-1-ol.
- Explains that the smaller alcohol's needed less energy to break the bonds in the reactants and so more energy is needed to initiate the reaction.
- Explains that carbon is a better insulator than copper, as it has lower thermal conductivity value and stops heat getting through to heat the water as there should be.
- Explains that their results show a clear increase in the energy released per unit mass of alcohol. they need to find which alcohol releases the most energy per mole.
- Explains that energy mass x temp increase depends on the substance you are heating, it is called the specific heat capacity.
- Explains that the mass of water heated, 100g, is the heat energy exchanged during the experiment, which needs to be converted to heat taken in per mole of alcohol burned.
- Explains that the heat absorbed by the calorimeter can be worked out.
- Explains that the two values worked out above for the energy absorbed by the water and the calorimeter give the total.
- Explains the average enthalpy of combustion for the alcohols in the table.
- Compares their results to the bond enthalpy values that they had worked out earlier.
- Explains that it is possible to measure the exact enthalpy of combustion using a bomb calorimeter apparatus. heat losses can be eliminated if the thermo chemical investigation is coupled with an electrical calibration.
- Compares the values of the enthalpy of combustion given by the bomb calorimeter to their results.
- Explains that methanol was the least accurate at 38.9% of what it should have been and propon-1-ol at 49.5%.
- Opines that their results have been consistently accurate, with the gap between the most accurate and the least accurate being only 10%. this gives them the impression that they are not just wrong because of human error.
- Explains that the enthalpy's of combustion that they are comparing their results to were measured under different conditions so this means they would be different any way.
- Explains that heat produced in the experiment was aloud to escape before it had even entered the apparatus and even heat that got into the water could escape back out of the calorimeter.
- Explains that they redid the experiments now using the insulation material, attaching it to the sides of the calorimeter. the results were an improvement on the previous attempt.
- Explains that their results show a clear increase of around 9% although this does vary from alcohol to alcohol. the heat produced does not even enter the apparatus, it is aloud to escape immediately.
- Opines that the accuracy of their experiment could have been improved by using a bomb calorimeter, which was not available to them.
- Compares the enthalpy of combustion from the bomb calorimeter to the results that they got from their experiments. the only thing that could have been improved was to measure all the heat energy that had been released by the combustion of the alcohols.
- Opines that lining the reflector with silver/ shiny surface would keep more of the heat produced during combustion close to the calorimeter so more is absorbed.
- Opines that there are other aspects of the enthalpy of combustion of alcohols that they could have investigated.
3890 wordsRead More - Heat Capacity of An Unknown Metalexplanatory essayThe purpose of performing this lab was to find the specific heat capacity of an unknown metal.
In this essay, the author
- Explains that the purpose of performing this lab was to find the specific heat capacity of an unknown metal.
- Describes how a hot plate is acquired, plugged in, and if left to warm up, fill two beakers with 0.075kg of water and record the temperature.
- Explains how to test a hot plate, two beakers with 0.075kg of water, select metal objects, and record the starting temperature of the water.
- Explains that the temperature increase wasn't great when the object was inserted into the second beaker because of the time restrictions put onto our experiment.
- Explains the lab propertiesitemweightstartingtemptemp of metal in cold watertemp changechain10g100 c24 degrees c23 degrees
- Describes the c=(945) / (3.367) (c=280.6object) and the chain: (0.075*4200*1), (0.01*76), (315) and (0.76) (414.5object).
- Explains that each metal has a different thermal conductivity which is the metal's ability to conduct and hold heat.
- Explains metal objects and suspected metal make ups: bolt: c=(0.075*4200*3) / (0.0455 * 74) copper:
- Concludes that their hypothesis was correct. a metals heat capacity is determined by the makeup and density of a metal.
1176 wordsRead More - Energy Conservation Labexplanatory essayThe purpose of this experiment is to try to find the original temperature of the hot water in the heater using the 60 degrees C thermometer. Use your 60°C thermometer, and any materials available in your laboratory, to determine the temperature of the water in the coffee pot. During this experiment we calculated the original temperature of a heater after it had been cooled down, and we did this by measuring hot, cold, and warm water, with a thermometer that had tape covering 60 degrees and up. When preformed each of these experiments with each temperature of water, plugging them into the equation (Delta)(Ti – hot – Tf) T Hot x Cp x Mass(Cold) = (Delta)(Tf – Ti – Cold) T Cold x Cp x Mass(Hot)(d
In this essay, the author
- Explains how they calculated the original temperature of a heater by measuring hot, cold, and warm water, with tape covering 60 degrees and up. the lab gave them the skills to work well in the professional environment and to be conscious of the environment.
- Explains lab 5's 'molecular model building' experiment. the handout provided charts for us to record data on the number of valance electrons present in a molecule.
- Explains the purpose of lab 6: to determine the amount of heat liberated by a particular fuel by measuring the increase of the water temperature earner provided by the fuel.
- Describes how the first week of the experiment was a collaboration of ideas and planning that helped develop skills in leadership and problem solving.
- Explains the main purpose of the experiment, which was aimed at comparing authentic and sample ions.
- Explains the formulas used to measure the amount of different ions in a fertilizer sample by counting to preform tests. the begging of the experiment requested that the percentage of so4 be found.
- Describes how the energy content of fuels experiment focused mainly on the amount of heat liberated by a particular fuel contained in alcohol lamps, which stored absolute ethanol, butanol or kerosene.
1207 wordsRead More - Enthalpy Essayexplanatory essayENTHALPY What is enthalpy? Enthalpy is the amount of heat content used or released in a system at persistent pressure. Enthalpy is typically articulated as the change in enthalpy. The change in enthalpy is linked to a change in internal energy (U) and a change in the volume (V), which is multiplied by the constant pressure of the system.
In this essay, the author
- Defines enthalpy as the amount of heat content used or released in a system at persistent pressure.
- Explains that when the reaction is giving off heat, it is exothermic, and the enthalpy change is negative. if energy flows from the surrounding environment and heat is being taken in, the change in energy is positive.
- Explains that bond enthalpy is the energy required to break a chemical bond. it is expressed in units of kj mol-1, measured at 298 k.
- Explains that bond making is an exothermic process. however, if a certain bond is broken and then reformed, then the same amount of energy must be involved.
- Explains that 2 o-h bonds are formed per water molecule, and there are 2 water molecules formed, therefore 4
- Explains that combustion is the process in which fuel is burnt in exchange for energy. there are two forms of combustion, "complete" and "incomplete".
- Explains that stand and boss are connected to the clamp. boss is used to secure the can in place and for safety.
- Recommends clamping the metal can (or flask) at a suitable height to allow room for the spirit burner to be placed below.
- Opines that there were factors in this practical that could have led to better results. loads of errors had occurred with the practical and means of improvement made the experiment better.
- Explains that thin layer chromotography is carried out by packing the same materials into a verticle glass column.
- Explains separations in tlc involve distributing a mixture of two or more substances between the stationary phase and the mobile phase.
- Explains that gas chromatography is a dominant tool in analysis. it contains different variations in the way it is done.
- Explains that gas chromatography has limited uses due to the decomposition temperature of the mixture and the composition of a column. most columns cannot withstand temperatures greater than 250-350 °c.
- Explains how the pen reacts with the solvent and separates the substances in the ink.
- Explains how it helps draw out straight lines (1cm from the top) and makes it more accurate.
- Explains how the thin layer chromatography strip is used to extract the green liquid and place small drops.
- Explains the use of thin layer chromatography to dry the liquid faster.
- Explains that the second solvent is used as the mobile phase to travel up the thin layer chromatography strip and separate out the substances.
- Explains that the glass beaker is used to contain the second solvent, and it is where the thin layer chromatography is held.
- Explains how to cut strips of thin layer of the chromatography plate to fit into tubes provided.
- Explains how they crush the contents together using the mortar until plenty of green fluid is made.
- Explains how to draw a line using sharp pencils, not pen, approximately 1cm above the bottom of the chromatography paper.
- Explains how to collect the green fluid and dab it on the thin layer chromatography strip in the middle of the pencil line drawn.
- Recommends using a hair dryer to dry the thin layer chromatography strip so the green fluid is not wet anymore.
- Explains how to add a few drops of solvent to the glass beaker once it is dry.
- Explains how to put the thin layer chromatography strip into the beaker filled with solvent and make sure that it is held up right.
- Explains that if the sample is solid, it is weighed using an accurate balance, and then dissolved to make up a known volume of solution.
- Explains how a safety pipette filler is used to draw the solution into it, which is then emptied into the conical flask.
- Explains that a few drops of an indicator may be added to the conical flask, which will show titration results.
- Explains that the second chemical is placed in a burette, which reacts with the synthesised chemical sample in the conical flask.
- Explains how the solution from the burette is run into the conical flask. the solution is added one drop at a time, with swirling to mix the solutions as the end-point is approached.
- Explains that a standard solution is an accurately known concentration prepared from the primary standard, which is stable, of high purity, highly soluble in water, and of molar mass to allow accurate weighing.
- Explains that the solution is in a virtually pure form and so there is no requirement to find out the concentration.
- Explains that a primary standard solution can be valued to high level of accuracy and reliability.
- Explains the difference between a primary standard solution, and one that is stable enough for titrimetric work.
- Explains that as the atomic mass is known, the volume of the solution can be calculated using this formula.
- Explains that if a solution was to be made of (nacl) with 6mol dm-3 and the volume is 50cm3, then:
- Recommends weighing sodium carbonate and placing it in a small beaker.
- Explains that colorimetry is the scientific method used to classify the colours of the spectrum.
- Explains that colorimetry is used in chemistry for things such as colour painting, food manufacturing, and textiles. the amount of light absorbed is measured as the absorbance.
- Explains how to weigh the spirit burner, remove the cap, light the wick, and allow the alcohol to heat the water.
- Explains how to record the final temperature of the water using the thermometer and work out the temperature change.
- Recommends that the experiment be carried out in a temperature-controlled area, as the atmosphere affects the practical. elimination of the flame as soon as possible is important. alcohol and water spillage should be avoided.
- Recommends repeating the experiment as many times as possible. 90% of the heat released from the spirit burner didn't grasp the metal can.
- Explains that thin layer chromatography provides a speedy answer to how many components are in the mixture.
- Explains that chromatography is used to separate mixtures of substances into their components.
- Explains that paper is replaced by a thin layer of powder, such as silica, on glass or plastic backing. it is used to determine amino acids in blood samples and in analysis of food dyes.
- Explains how a thin layer chromatography plate (cut into strips) is used to make markings on the strip. the pen reacts with the solvent and separates the substances in the ink.
- Explains how to draw around each colour spot, that has appeared, and label/ not down the colour of each spot.
- Explains the importance of a high level of purity in synthesised chemical compounds, such as pharmaceuticals. a titration measures the volume of one solution that reacts with another solution.
- Explains how titration results can be used to calculate the amount of the synthesised chemical in the sample, and therefore find its purity.
- Explains that they are using the standard solution for titration, because the term ‘standard solution’ is a scientific phrase.
- Explains that nacl must be used to make a solution of 50cm3 standard solution.
3212 wordsRead More - Chemistry: Magnesium Hydroxide And Citric Acidexplanatory essayThe first law of thermodynamics simply states that heat is a form of energy and heat energy cannot be created nor destroyed. In this lab we were measuring the change in temperature and how it affected the enthalpy of the reaction.
In this essay, the author
- Explains how they determined the amount of heat exchanged in four different chemical reactions using two different compounds and water. safety concerns included inhaling citric acid, mixing magnesium hydroxide, and properly disposing of chemical mixtures.
- Explains that method one and method two are calculations for the class data. below them are the calculations i did for each reaction.
- Explains that the second law of thermodynamics states all real processes, so chemical reactions for this lab occur spontaneously in the sense that increases the entropy.
- Opines that it is preferable to use this experiments chemical reaction between magnesium hydroxide and citric acid because these to compounds can be reused.
- Explains that the first law of thermodynamics states that heat is a form of energy and heat energy cannot be created nor destroyed.
- Explains that the water is pure with no contaminates and that it is just a vessel for the chemical reaction between magnesium hydroxide and citric acid.
984 wordsRead More - 6.03 Goldfish Experimentcomparative essay4. Place a thermometer into the Ziploc bag and record the number of times the goldsifh
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- Explains how to take the goldfish out of its container and place it in the ziploc bag that is filled.
- Explains how to put the ziploc bag in a beaker that is 1/3 filled with room temperature water.
- Explains how to remove the ziploc bag from the beaker and add crushed ice.
- Describes the number of times the goldfish opens and closes its mouth in one minute.
- Recommends placing a thermometer into the ziploc bag and recording the number of times the goldsifh opens and closes its mouth.
- Explains how to check the goldfish's temperature with a thermometer and record the number of times it opens and closes its mouth in one minute.
218 wordsRead More - Phase Change Lab Reportanalytical essayMethodology: A plastic cup was filled half way with crushed ice and mixed with four spoonfuls of 5 mL of sodium chloride. A thermometer was quickly placed inside the cup to take the temperature and the
In this essay, the author
- Explains that a phase change occurs when the kinetic energy decreases or increases to change the state of matter. the freezing and melting point of something is the temperature at which these phase changes occur.
- Describes how a plastic cup was filled half way with crushed ice and mixed with 4 spoonfuls of 5 ml of sodium chloride. a thermometer was placed inside the cup to take the temperature and the result was recorded on an observation sheet.
- Describes the temperature of the frozen water table, the ice bath temperature, and the written observations.
- Analyzes the temperature of the water in the vial and the ice/salt mixture every 3 minutes over a period of 30 minutes.
- Explains that the lab's main findings are that water will freeze at 0 degrees celsius. this can be proven directly from the graph and the table.
704 wordsRead More - Temp: Mass of evap. dish: Mass of evap dish+contents: Mass of contents: Solubility g/100cm3 water
In this essay, the author
- Explains how to divide 30g of white substance into 4 test tubes evenly, 7.5g into each test tube along with the water.
- Explains that one at a time, place your test tubes in the water bath and heat the first test tube to 25 degrees c.
- Recommends pouring excess water into a dry evaporating dish after heating them to the right temperatures.
- Calculates the solubilty in grams per 100 cm3 of water by subtracting the mass of the evaporating dish and its contents.
- Describes the mass of evap. dish and its contents.
- Explains that the substance that we worked with ( substance a ) is potassium nitrate.
- Explains that if the solubility curves differ a lot, chances are, your substances are different.
348 wordsRead More