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Full file at http://testbank360.eu/solution­manual­experiments­in­general­chemistry­2nd­edition­stanton EXPERIMENT

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Specific Heat of Substances Equipment 1. 2. 3. 4. 5. 6. 7.

MeasureNet temperature probe Two 110 °C alcohol or mercury thermometers Two 12 oz (355 mL) styrofoam cups One 3” × 3” cardboard lid with a 1 cm diameter hole in the center One 150-mL beaker, one 250-mL beaker, one 600-mL beaker Balances capable of measuring to the nearest 0.001 g Magnetic stirrers and stir bars (if available), or a 10 inch copper wire with a 1 cm diameter loop on one end 8. Beral pipets (disposable) 9. Hot plate or Bunsen burner List of Chemicals – Per 100 Students (Assumes 50% Waste) 1. 1 kilogram of each of the following solids to be used as unknowns a) aluminum shot b) calcium carbonate chips (marble chips) c) copper shot d) iron flakes e) lead shot f) zinc (mossy) 2. 600 mL of each of the following liquids to be used as unknowns a) 1.5-pentanediol b) 1-hexene c) 1-propanol d) acetone e) ethanol f) glycerol g) distilled water 3. Containers marked “Used Unknown Metals” bearing the same Unknown Numbers as the metals in the List of Chemicals 1 above 4. Waste containers for the unknown liquids in the List of Chemicals 2

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EXPERIMENT 2

Lab Report Part A - Determination of the Calorimeter Constant Experimental data and calculations - Trial 1 mass styrofoam cup calorimeter 6.130 g mass styrofoam cups and room temperature water 50.461 g mass water 44.331 g mass of a beaker 50.411 g mass of beaker and warm water 97.147 g mass of water 46.736 g warm water temperature 60.1 ˚C cool water initial temperature 20.1 ˚C system’s equilibrium (final) temperature 40.0 ˚C Tcool water 19.9 ˚C Twarm water 20.1 ˚C Ccal = -(46.736 g) (4.18 J/g°C) (-20.1 °C) - (44.331 g) (4.18 J/g°C) (19.9 °C) = 240. J Ccal =

240. J = 12.1 J/ oC  19.9 C

Experimental data and calculations - Trial 2 mass styrofoam cup calorimeter 6.130 g mass styrofoam cups and room temperature water 50.461 g mass water 44.331 g mass of a beaker 50.411 g mass of beaker and warm water 97.147 g mass of water 46.736 g warm water temperature 60.1 ˚C cool water initial temperature 20.1 ˚C system’s equilibrium (final) temperature 40.0 ˚C Tcool water 19.9 ˚C Twarm water 20.1 ˚C Ccal = -(46.736 g) (4.18 J/g°C) (-20.1 °C) - (44.331 g) (4.18 J/g°C) (19.9 °C) = 240. J Ccal =

240. J = 12.1 J/ oC 19.9  C

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Average calorimeter constant 12.1 J/˚C

12.1

 12.1 J/  C  12.1 J/  C 2

Part B - Determination of the Specific Heat of a Solid Unknown number AZ687 Experimental data and calculations - Trial 1 mass styrofoam cup calorimeter mass styrofoam cups and room temperature water mass of water mass of test tube and solid sample mass of solid sample temperature of hot metal temperature of cool water system’s equilibrium (final) temperature file name trial 1 Sta12300 Twater 2.2 ˚C Tsolid 49.1 ˚C Cm 

6.272 g 55.621 g 44.394 g 163.081 g 24.737 g 78.0 ˚C 26.7 ˚C 28.9 ˚C

(44.394 g) (4.18 J/g  C) (2.2  C)  (12.1 J/  C) (2.2  C)  0.36 J/g  C (24.737 g) (49.1  C)

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Full file at http://testbank360.eu/solution­manual­experiments­in­general­chemistry­2nd­edition­stanton Experimental data and calculations - Trial 2 mass styrofoam cup calorimeter mass styrofoam cups and room temperature water mass of water mass of test tube and solid sample mass of solid sample temperature of hot metal temperature of cool water system’s equilibrium (final) temperature file name trial 1 Sta12300 Twater 2.2 ˚C Tsolid 49.1 ˚C Cm 

6.272 g 55.621 g 44.394 g 163.081 g 24.737 g 78.0 ˚C 26.7 ˚C 28.9 ˚C

(44.394 g) (4.18 J/g  C) (2.2  C)  (12.1 J/  C) (2.2  C) (24.737 g) (49.1  C)

 0.36 J/g  C

Average specific heat of solid 0.36 J/g˚C

 0.36

 0.36  J/g  C  0.36 J/g  C 2

Using the specific heat values given in Table 1, identify the unknown solid. zinc or copper, the average specific heat is close to either.

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EXPERIMENT 2

Pre-Laboratory Questions 1. 30.109 grams of cool water are placed in a styrofoam cup calorimeter. 30.789 grams of water are heated in a beaker to 53.11 °C. The warm water is added to the cool water in the calorimeter, and the temperature change of the system is monitored (see plot below). Calculate the calorimeter constant. This calorimeter constant will be used in Question 2.

34.80 °C 20.14 °C

 30.789g (4.18J/g o C) (18.31o C)  30.109g (4.18J/g o C) (14.66 o C)  511 J C cal 

511 J 14.66 o C

 34.9J/ o C

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Full file at http://testbank360.eu/solution­manual­experiments­in­general­chemistry­2nd­edition­stanton 2. 25.000 grams of water are added to a styrofoam cup calorimeter. 41.397 grams of an unknown solid are heated in a large test tube to 99.60 °C. The hot solid is added to the water in the styrofoam cup calorimeter, and the temperature change of the system is monitored. Calculate the specific heat of the unknown solid. Using the information from Table 1, identify the unknown solid.

28.82 °C 19.19 °C

C solid 

25.000g (4.18J/g o C) (9.63 o C)  34.9J/ o C (9.63 o C) 41.397g (70.78 o C)

C solid  0.458 J/g o C The unknown solid is iron.

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EXPERIMENT 2

Post-Laboratory Questions 1. Step 13 of the procedure, you were instructed not to let the thermometer touch the bottom or the walls of the test tube when heating the unknown solid. Why was this instruction given? The temperature of the test tube walls may be higher (more direct heating) than the temperature of the unknown solid in the test tube.

2. In an experiment, 10.0 grams of solid A and 10.0 grams of solid B are each heated to 200 °C. Each solid is added to different beakers containing 25 grams of water at 25 °C. The equilibrium temperature of solid A is significantly higher than that of solid B. Which solid has the higher specific heat? Justify your answer with an explanation. Solid A has higher specific heat because it releases more heat to the water in the beaker, leading to higher equilibrium temperature.

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Full file at http://testbank360.eu/solution­manual­experiments­in­general­chemistry­2nd­edition­stanton 3. If a student incorrectly calibrated the temperature probe so that all subsequent temperature readings are 2.0 °C to high, will it affect the student’s specific heat value determined in this experiment? Justify your answer with an explanation. If the temperature probe readings are 2.0 °C too high, the change in temperature of the water and calorimeter will not be affected because both the initial and the final temperatures of the water and calorimeter are measured by the temperature probe. However, the final temperature of the solid will be 2.0 °C too high, which will cause the change in temperature of the solid to be 2.0 °C too small. This will lead to a higher calculated specific heat of the solid.

4. The percent error in this experiment is calculated by taking the absolute value of the difference between your experimental specific heat value and the actual value of the specific heat (from Table 1) for the solid you identified as your unknown, dividing that number by the specific heat value of the unknown solid from Table 1, then multiplying that number by 100%. Calculate the % error in the experimental specific heat value for your unknown solid. Assuming the unknown in this experiment was copper, the correct specific heat for copper is 0.385 J/g°C. The experimental value obtained in this experiment was 0.36 J/g°C. The % error in the experimental value is calculated according to the following equation. 0.36 J/g  C  0.385 J/g  C 0.385 J/g  C

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 100 %  6 %


Solution manual experiments in general chemistry 2nd edition stanton