A) In the laboratory a student uses a \"coffee cup\" calorimeter to determine th
ID: 958081 • Letter: A
Question
A) In the laboratory a student uses a "coffee cup" calorimeter to determine the specific heat of a metal. She heats 19.8 grams of copper to 98.16°C and then drops it into a cup containing 76.2 grams of water at 21.79°C. She measures the final temperature to be 23.63°C. Assuming that all of the heat is transferred to the water, she calculates the specific heat of copper to be ____________J/g°C
B)When a solid dissolves in water, heat may be evolved or absorbed. The heat of dissolution(dissolving) can be determined using a coffee cup calorimeter.
In the laboratory a general chemistry student finds that when 5.85 g of K2SO4(s) are dissolved in 104.40 g of water, the temperature of the solution drops from 22.63 to 20.65°C.
The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be 1.59 J/°C.
Based on the student's observation, calculate the enthalpy of dissolution of K2SO4(s) in kJ/mol.
Assume the specific heat of the solution is equal to the specific heat of water.
Hdissolution = _____________kJ/mol
C)
A bomb calorimeter, or a constant volume calorimeter, is a device often used to determine the heat of combustion of fuels and the energy content of foods.
Explanation / Answer
A.) Heat transferred for system = heat transferred for (copper + water)
Q = mcT + mcT
19.8g * (98.16 - 23.63)°C * c = 76.2 g * (23.63 - 21.790)°C * 4.180J/(g.°C)
specific heat of copper = 0.4185 J/g°C
B.) mass of mixture = 5.85 g + 104.40 g = 110.25 g
Q = mass of mixture * specific heat of mixture (J/g°C)
Q = 110.25 * 1.98 * 1.59
= 347.089 J
moles of K2SO4 = 5.85 / 174.259= 0.03357 moles
Hdissolution =347.089 / 0.03357= 10.339 kJ/mol
C.)
T = 29.08 - 26.22 °C = 2.86 °C
Heat gained by Fructose = 2.86 °C * 864.4 J/°C = 2472.184 J
Heat gained by water = 2.86 * 4.18 * 1.254* 103 = 1544.106 J
Total heat evolved = 2472.184 J + 1544.106 J = 4016.29 J
no of moles of fructose = 1.0830 / 180 = .006 moles
Hence Molar Heat of Combustion = 4.026/.006 = 671 kJ/mol
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.