Enthalpy of formation of calcium carbonate Essay

verifiable To determine the hydrogen of system of atomic number 20 degree centigradeate Procedures A. Reaction of atomic number 20 with trim hydrochloric deadly 1. 1. 0909 g of atomic number 20 metal was weighed out perfectly. 2. 100 cm3 of more or less 1 M hydrochloric acidulated was pipetted. and placed in a plastic beaker. 3. The initial temperature of the acid was fit(p) 4. The weighed atomic number 20 was added into the acid and ablaze thoroughly with the thermometer until al unmatchableness the metal had reacted. 5. The maximum temperature attained by the firmness of purpose was recorded. 6. The try was tell with 1. 0538g calcium metal. Results Experiment no(prenominal)e 1 2.Mass of Ca use/ g 1. 0909 1. 0538 Initial temp. of resultant/ ? 27 26 terminal temp. of solution/ ? 55 52 Temperature trans version/ ? 28 26 Calculations and Discussion 1. What does the term pepperiness of organic practice of integrity of a substance mean? Heat of defining refer s to the groove change over when iodin seaw altogether of a substance is formed from its constituent elements is their standard states beneath standard conditions. 2. What ar standard conditions for thermochemical calculations? Standard conditions is restrictd as elements or compounds appear in their practice physical states at a pressure of 1 atm (101325 Nm-2/760mmHg) and at temperature of 25 oC (298 K).Moreover, the solution should cod unit activity(1mol dm-3 ). 3. Write the equality for the arrangement of calcium change beneath standard conditions. (Call this Equation 1) Ca(s) + C(s) + 3/2 O2(g) CaCO3(s) 4. Write an ionic equation for the reception taken place. (Call this Equation 2) Ca(s) + 2H+(aq. ) ? Ca2+(aq. ) + H2(g) 5. Assuming (a) the solution in the plastic beaker has the kindred specific warmness message as water, i. e. , 4. 2 kJg-1K-1 and (b) density of the acid is the same as that of water, i. e. , 1. 0 g cm-3.Calculate, in apiece audition, the he at change in the reaction mingled with the calcium and the acid per gram of calcium. For the world-class experiment ? sinew evolved by the reaction= Energy abstracted by the acid ?By E = mc? T, ?H per gram of calcium = (100/1000)(4200)(28)/ 1. 0909 = -10780J g-1 = -10. 780kJ g-1 For the plump for experiment ?Energy evolved by the reaction= Energy jailed by the acid ?By E = mc? T, ?H per gram of calcium = (100/1000)(4200)(26)/ 1. 0538 = -10362J g-1 = -10. 362kJ g-1 6. Calculate the number heat evolved by champion mole of calcium.For the first experiment?H per one mole of calcium =(100/1000)(4200)(28)/ 1. 0909/40. 08 =-432066 J mol-1 =-432. 066 kJ mol-1 For the second experiment ?H per one mole of calcium =(100/1000)(4200)(26)/ 1. 0538/40. 08 =-415329 J mol-1 =-415. 329 kJ mol-1 Average ? H per one mole of calcium (? Hx) =(432. 066 +415. 329)/2 =-423. 698 kJ mol-1 7. why is the exact concentration of the hydrochloric acid unimportant? near concentration of hydrochloric acid is not considered as one of the errors. In the reactions, limiting agents, i. e. calcium and calcium carbonate, essential be reacted completely.Only these matter in the reaction but not the amount of H+(aq) provided in hydrochloric acid. Indeed, the concentration of the hydrochloric acid just affects the rate of the reaction. and then the exact concentration of hydrochloric acid is unimportant provided that thither is enough H+(aq) to react with limiting agents completely. 8. Should we handbill the rule book of acid with a measuring piston chamber? wherefore? The measuring cylinder should not be used to measure the volume of acid. This is because the heat confined by the acid must be counted when calculative the heat change of the reaction.As the acid has very(prenominal) high specific heat capacity, the errors in cipher the heat change of the reaction will be very signifi basist if the heat absorbed by acid is not taken into account. Thus, the volume of acid should be obtain ed precisely to apply into E=mc? T in order to calculate the heat absorbed by the acid accurately. As the racing shell of the measuring cylinder is far from accurate, the pipette should be used or else. B. Reaction of calcium carbonate with dilute hydrochloric acid 1. 3. 0940g of dry powder calcium carbonate was weighed out accurately and placed directly into a clean dry plastics cup.2. 100 cm3 of approximately 1 M hydrochloric acid was pipetted into another beaker. 3. The acid was poured on the carbonate in the plastic beaker. 4. The solution was stirred briskly with the thermometer and the maximum temperature reached by the solution. was recorded. 5. The experiment was repeated with 2. 7400g of dry powdered calcium carbonate. Results Experiment no. 1 2 Mass of CaCO3 used/ g 3. 0940 2. 7400 Initial temp. of solution/ ? 26 25 terminal examination temp. of solution/ ? 28 27 Temperature change/ ? 2 2 Calculations and Discussion 1. Write an ionic equation for the reaction taken pl ace.(Call this Equation 3) CO32-(aq. ) + 2 H+(aq. ) ? CO2(g) + H2O(l) 2. Calculate the average heat evolved by one mole of calcium carbonate. (Making the same assumptions as in Part A) For the first experiment ?Energy evolved by the reaction= Energy absorbed by the acid ?By E = mc? T, ?H per mole of calcium carbonate = (100/1000)(4200)(2)/(3. 0940/(40. 08+12. 01+163) =840 /(3. 0940)/(100. 09) =-27174 J mol-1 =-27. 174 kJmol-1 For the second experiment ?Energy evolved by the reaction= Energy absorbed by the acid ?By E = mc? T, ?H per mole of calcium carbonate = (100/1000)(4200)(2)/(2.7400/(40. 08+12. 01+163) =840 /(2. 7400)/(100. 09) =-30685 J mol-1 =-30. 685 kJmol-1 Average ? H per one mole of calcium (? Hy) =(27. 174 +30. 685)/2 =-29. 080kJ mol-1 3. Draw an cogency-cycle linking Equations 1, 2 and 3 together, you must include reactions that had not been performed in the experiment. 2H+(aq. ) +Ca(s) + C(s) + 3/2 O2(g) CaCO3(s) + 2H+(aq. ) ?Hx ? Hy Ca2+(aq. ) + H2(g) + C(s) + 3/2 O2 (g) Ca2+(aq. ) + CO2(g) + H2O(l) 4.. to a fault your data-based results, what other information do you carry to enable you to calculate the heat of formation of calcium carbonate?Look up these necessary information from any suitable source. The heat content change of formation of water -286 kJ mol-1 The enthalpy change of formation of carbon dioxide -393 kJ mol-1 5. Calculate the heat of formation of calcium carbonate. ?H? f CaCO3(s) =? Hx +? H? f CO2(g) +? H? f H2O(l) -? Hy =-423. 698-393-286+29. 080 =-1073. 6 kJ mol-1 6. As far as you bear, appoint out the major sources of inaccuracy in the experiment and nominate ways to improve them whenever possible. Sources of error Heat expiry to surrounding by evaporation, conduction and radiation.-The thermometer absorbed any(prenominal) zilch. The specific heat capacity and the density of the solution are not actually the same as those of the water. -Some of the samples failed to dissolve completely? The reading of the therm ometer is not accurate enough. -The experiment was not exactly carried out under standard conditions. -Some heat was gained by the gases, a gigantic amount of heat is loss to purlieu when the gases are releasing. -The lid covering the plastic cups cannot prevent heat loss efficiently. -Heat capacities of plastic cups and thermometer were ignored.-The samples were not pure calcium and pure calcium carbonate due to institutionalize oxidation and reaction with moisture in air. Improvements -Use the vacancy flask calorimeter with a cork stopper instead of the polystyrene foam cup -Use a more accurate reading thermometer (e. g. Beckmann thermometer) Find out the specific heat capacity of other materials other than water. -Use sand musical composition to remove the oxide layer on calcium metal. -Use powdered calcium instead of the granules in order to plus the rate of reaction ,so that the heat loss to the surroundings can be reduced7. State the law which you have used in order to rejoinder Question (5). The heat of formation of calcium carbonate cannot be determined directly by calorimetric experiments as there are several experimental difficulties -The extent of the reaction cannot be controlled -Heat evolved cannot be apart(p) into appropriate terms -Direct combustion of calcium can be violent -Side reactions may arise, for example, 2Ca(s) + O2(g) 2CaO(s) C(s) + O2(g) CO2(g) Then ,Hesss Law is applied to calculate the heat of formation of calcium carbonate.Hesss law states that the energy change for any chemical or physical exploit is independent of the pathway or number of steps required to complete the process provided that the final and initial reaction conditions are the same. In other words, an energy change is path independent, only the initial and final states being of importance. This path independence is true for all state functions 8. State the law which you have used in order to answer Question (7) depends? why is this principle useful? The law of conservation of energy states that energy can neither be created nor sunk but can be changed from one form to another.In order to achieve the answer, Hesss law is used. Hesss law states that the total enthalpy change of a reaction is independent of the route by which the reaction takes place. In other words, the standard enthalpy change of a reaction depends on the differences in standard enthalpy between the reactants and the products. It means that the enthalpy of the reaction system is conserved. As the absolute enthalpy of a substance is not possible to be determined and only the difference between reactants and products can be measured experimentally.This law helps us to define the standard enthalpy change of a reaction. finis The enthalpy of formation of calcium carbonate is -1073. 6kJ mol-1. denotation http//hk. knowledge. yahoo. com/question/? qid=7006100200879 http//hk. knowledge. yahoo. com/question/question? qid=7007111800043 http//www. answers. com/8. %09Should +we+measure+the+volume+of+acid+with+a+measuring+cylinder%3F+Why%3F http//hk. search. yahoo. com/search/kp? ei=UTF-8&p=word%E6%89%93%E5%88%86%E7%B7%9A&rd=r1&fr2=tab-web&fr=FP-tab-web-t F. 6 chemistry Notes Section III by Ms crime W L.