Answer all/show work: Save image, to read better. 1) 2) 3) Coffee Cup Calorimetr

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1)

2)

3)

Coffee Cup Calorimetry Calorimetry is a method used to measure enthalpy, or heat, changes that occur during chemical processes. Two common calorimeters are constant-pressure calorimeters and constant-volume (or "bomb") calorimeters. Bomb calorimeters are used to measure combustion and other gas-producing reactions, where the reaction is observed in a strong, sealed vessel. A simple constant-pressure calorimeter can be made from a foam coffee cup and a thermometer; energy changes in a reaction are observed via a temperature change of the solution in the cup. The idea behind calorimeters is that if they are sufficiently insulated from the outside environment, any energy gained or lost in the chemical reaction will be directly observable as a temperature and/or pressure change in the calorimeter. Part A A total of 2.00 mol of a compound is allowed to react with water in a foam coffee cup and the reaction produces 105g of solution. The reaction caused the temperature of the solution to rise from 21.0 to 24.7 degree C. What is the enthalpy of this reaction? Assume that no heat is lost to the surroundings or to the coffee cup itself and that the specific heat of the solution is the same as that of pure water. Enter your answer in kilojoules per mole of compound to three significant figures. plusminus Heat of Solution Calorimetry is a method used to measure changes in enthalpy, or heat, that occur during chemical processes. Two common calorimeters are constant-pressure calorimeters and constant-volume (or "bomb") calorimeters. Bomb calorimeters are used to measure combustion and other gas-producing reactions, in which the reaction is observed in a strong, sealed vessel. A simple constant-pressure calorimeter can be made from a foam coffee cup and a thermometer, in which energy changes in a reaction are observed via the change in temperature of the solution in the cup. The idea behind calorimeters is that if they are sufficiently insulated from the outside environment, any energy gained or lost in the chemical reaction will be directly observable as a temperature and/or pressure change in the calorimeter. Part A In the following experiment, a coffee-cup calorimeter containing 100 inL of H2O is used. The initial temperature of the calorimeter is 23.0 degree C. If 6.90g of CaCl2 is added to the calorimeter, what will be the final temperature of the solution in the calorimeter? The heat of solution Hsoln of Cacl2 is -82.8 kj/mol. Express your answer with the appropriate units. Specific Heat The heat capacity of an object indicates how much energy that object can absorb for a given increase in that object's temperature. In a system in which two objects of different temperatures come into contact with one another, the warmer object will cool and the cooler object will warm up until the system is at a single equilibrium temperature. Note the difference between the terms molar heat capacity, which has units of J/(mol degreeC), and specific heat, which has units of J/(g degree C). Part A A volume of 125mL of H2O is initially at room temperature (22.0 degree C). A chilled steel rod at 2.00 degree C is placed in the water. If the final temperature of the system is 21.4 degree C , what is the mass of the steel bar? Use the following values: specific heat of water = 4.18 J/(g degreeC) specific heat of steel = 0.452 J/(g degreeC) Express your answer to three significant figures and include the appropriate units. Part B The specific heat of water is 4.18 J/(g degree C). Calculate the molar heat capacity of water. Express your answer to three significant figures and include the appropriate units.

Explanation / Answer

1.

A)

2*H = 105*(24.7-21.0)*4.18

H = 1623.93/2 = 811.965 J/mol = 0.811 KJ/mol.

Hence, enthaalpy of reaction = 0.811 KJ/mol.

2.

A) (6.90/111)* 82.8*1000 = 100* delta-T*4.18

delta-T = 51.47027/4.18 =12.31 degree C

hence, final temp = 23 + 12.31 = 35.31 degree Celcius.

3.

A) (21.4 - 2)*125*4.18 = 0.452*(21.4 - 2)*x

x = 10136.5/8.7688 = 1155.97 grams = 1.155 Kg

Mass of steel rod =  1.155 Kg

B) specific heat = 4.18 J/g-degreeC

molar heat capacity of water = 4.18*18

= 75.24   J/mol-degreeC

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