Chemistry
Lab 9 Heat of ReactionOBJECTIVE:To experimentally determine the heat of reaction for two exothermic reactions.DISCUSSION:The heat given off or gained in a reaction is called the heat of reaction (?????????????????????????????????????).A reaction that releases heat is known as an exothermic reaction; an endothermic reactionis one that absorbs heat.The heat of the reaction corresponds to one mole of the reactant and is expressed inkilocalories per mole of reactant or in kilojoules per mole of reactant: ????????????????????????????????????? = ???????????????????????????????????? (????????????????)???? (????????????) , where qreaction is the heat produced or absorbed by a certain amount of moles ofreactant, n.The reactions for this experiment are outlined as (1) and (2) and are as follows:(1) ???????????????? (????) + ???????????? (????) ? ???????? + (????????) + ????????? + ???????????? (????) (????????) ????????? =?(2) ???????????????? (????) + ???????????? (????????) ? ????????+ (????????) + ????????? (????????) + ???????????? (????) ????????? =?To determine ?Hreaction the heat released or absorbed by the reaction must be measured.When an exothermic reaction occurs in a container, the heat which is released warms up thecontainer and its contents (the temperature increases). The contents of the container includethe reaction products and a solvent (water in our case). The measurement of the heat transferunder controlled conditions is called calorimetry (from the energy unit, calorie), and acontainer used to measure the heat transfer is called a calorimeter. The calorimeter preventsheat transfer to or from the surroundings, thereby isolating the system that us beingmeasured.When a reaction occurs in a relatively large amount of solvent (water), we can consider wateras the sole medium absorbing the heat of the reaction. This allows us to apply the law ofconservation of energy (heat released by the reaction is equal to the heat absorbed by thewater) and to calculate the heat of reaction by measuring the temperature change of thewater (even though it is actually a diluted aqueous solution of the products), according tothe following relationships:(3) ???????????????????????????????????? = ????????????????????????? (4) ???????????????????????? = ???????????????????????? ? ???????????????????????? ? ?????????????????????????Where: swater is the specific heat of water, 1.00 ?????????????????? or 4.184?????????? ; mwater is the mass of waterused (recall that an acid solution (HCl (aq)) is mostly water); ????????????????????????? is the difference between the initial and final temperatures of the water solution in the calorimeter.PROCEDURES:REACTION 1:1. Open the virtual lab workspace for the heat of reaction activity. (Posted on the course website)2. From the glassware menu, obtain a 50 mL graduated cylinder and a foam cup (glassware). Take out the distilled water and solid NaOH (stockroom) and thebalance (tools).3. Transfer 50.0 mL of water to the graduated cylinder. Record the initial temperature. 4. Weigh between 1.00 and 1.50 grams of solid NaOH in the foam cup (tare the foamcup first, on the balance). Record the mass of NaOH.5. Pour the water into the foam cup and record the highest temperature; this is the final temperature.REACTION 2:1. Take the 0.50 M HCL from the stockroom, measure 50.0 mL with the graduated cylinder, and record the initial temperature.2. Empty the foam cup (right click). The procedure is the same as in reaction 1, except that HCl is being used in place of water.3. Record the mass of NaOH used, and the initial temperature of the acid, and the final temperature after the NaOH has been added.Name:Lab 9 Heat of ReactionDATA:Solid NaOH (g) Liquid (mL) ???????????????????????????????? (?) ???????????????????????????? (?) ????? (?)Reaction #1H2O:Reaction #2HCl:1. Using dimensional analysis, calculate the number of moles of NaOH (nNaOH) used inreaction #1 (show your work): ???????????????????? (????????????) = ???????????????????? (????) × 1 ???????????????????????????????????? (????) Where nNaOH isthe number of moles NaOH , mNaOH is the mass of sodium hydroxide used, and MMNaOHis the molar mass of sodium hydroxide.2. Using the density of water (???? = 1.000 ???????????? ), calculate the mass of the 50.0 g water usedin reaction #1 using: ???????????????????????? = ???????????????????????? × ????????????????????????.3. Using the specific heat of water (???????????????????????? = 1.000 ?????????????????? ), calculate the heat absorbed by thewater and the heat produced by the solution in reaction #1 using: ???????????????????????? = ???????????????????????? ? ???????????????????????? ? ????????????????????????? and ???????????????????????????????????? #1 = ?????????????????????????.a. ????????????????????????:b. ???????????????????????????????????? #1:4. Convert the heat produced by reaction #1 to kcal using: ???????????????????????????????????? #1(????????????????) =???????????????????????????????????? #1 (????????????) ? 1 ????????????????1000 ????????????5. Calculate ????????????????????????????????????? #1 using: ????????????????????????????????????? #1 = ???????????????????????????????????? #1 (????????????????)???????????????????? (????????????)6. Using dimensional analysis, calculate the number of moles of NaOH (nNaOH) used inreaction #2 (show your work): ???????????????????? (????????????) = ???????????????????? (????) × 1 ???????????????????????????????????? (????) Where nNaOH isthe number of moles NaOH , mNaOH is the mass of sodium hydroxide used, and MMNaOHis the molar mass of sodium hydroxide.7. Using the density of water (???? = 1.000 ???????????? ), calculate the mass of the 50.0 mL HCl usedin reaction #2 using: ???????????????? = ???????????????? × ????????????????????????.8. Using the specific heat of water (???????????????????????? = 1.000 ?????????????????? ), calculate the heat absorbed by theHCl and the heat produced by the solution in reaction #2 using: ???????????????????????? = ???????????????????????? ? ???????????????????????? ? ????????????????????????? and ???????????????????????????????????? #1 = ?????????????????????????.a. ????????????????????????:b. ???????????????????????????????????? #2:9. Convert the heat produced by reaction #2 to kcal using: ???????????????????????????????????? #1(????????????????) =???????????????????????????????????? #2 (????????????) ? 1 ????????????????1000 ????????????10. Calculate ????????????????????????????????????? #2 using: ????????????????????????????????????? #2 = ???????????????????????????????????? #1 (????????????????)???????????????????? (????????????)11. Convert the ????????????????????????????????????? #1 from kcal/mol to kJ/mol using the conversion: 1.000 kcal = 4.184 kJ12. Convert the ????????????????????????????????????? #2 from kcal/mol to kJ/mol using the conversion: 1.000 kcal = 4.184 kJ
