Calculate the mass of water (H,O, CHO = 4.181 J g-l °C-) at 20.0°C that would be requireć to cool a 30.0-g block of copper (Cu, co=0.385 Jg-l °C-1) from 50.0°C to 25.0°C in an insulated cup. %3D %3D 10

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Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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2. A small immersion heater was used to heat water in an insulated cup. The heater was placed in 100.0 g
of distilled water initially at 21.0°C, and turned on for 60.0 seconds while the water was stirred with a
thermometer. The final temperature of the water was measured to be 37.5°C. Assume the specific heat
capacity of the water is 4.18 J/g °C.
(a) Calculate the total heat energy in joules absorbed by the water and the average power in watts
(1 watt = 1 joule/s) delivered by the heater.
The heater was used to deliver 3000 joules of energy to 100.0 g of methanol (CH,OH(E)) in the same
manner. The temperature of the methanol increased by 11.8 Celsius degrees.
(b) Calculate the specific heat capacity of the methanol liquid.
(c) (i) Calculate the mass of water (H,O, Co= 4.181 Jgl °C-) at 20.0°C that would be requireć
%3D
to cool a 30.0-g block of copper (Cu, co0.385 J gl °C-l) from 50.0°C to 25.0°C in an
insulated cup.
%3D
(ii) Which liquid, water or methanol, would be more effective as a cooling agent for hot metal?
That is, which liquid would require less mass to achieve the same amount of cooling?
Justify your answer in terms of the quantity of heat required and/or the definition of specific
heat capacity.
A student wishes to make a solution of potassium hydroxide, (KOH, M=56.11 g/mol) in methanol, a
measure the enthalpy of dissolution of the solid. The student weighs out 4.00 g of KOH(s) and 100.0
of CH,OH(e), carefully adds the KOH to the CH,OH in an insulated cup with stirring, and measures :
temperature rise of 12.0 Celsius degrees.
(d) Calculate the enthalpy change in kJ/mol for the dissolution reaction of KOH(s) in CH,OH(8)
described above and represented below. Assume the specific heat capacity of the final solution is
2.23 J gl °C-. Express your answer with the correct sign and units.
KOH(s) → K*(in CH,OH) + OH-(in CH,OH)
(e) Calculate the molarity of the KOH(in CH,OH) solution made in part (d) above. Assume the
density of the final solution is 0.795 g/mL.
Unau
Transcribed Image Text:2. A small immersion heater was used to heat water in an insulated cup. The heater was placed in 100.0 g of distilled water initially at 21.0°C, and turned on for 60.0 seconds while the water was stirred with a thermometer. The final temperature of the water was measured to be 37.5°C. Assume the specific heat capacity of the water is 4.18 J/g °C. (a) Calculate the total heat energy in joules absorbed by the water and the average power in watts (1 watt = 1 joule/s) delivered by the heater. The heater was used to deliver 3000 joules of energy to 100.0 g of methanol (CH,OH(E)) in the same manner. The temperature of the methanol increased by 11.8 Celsius degrees. (b) Calculate the specific heat capacity of the methanol liquid. (c) (i) Calculate the mass of water (H,O, Co= 4.181 Jgl °C-) at 20.0°C that would be requireć %3D to cool a 30.0-g block of copper (Cu, co0.385 J gl °C-l) from 50.0°C to 25.0°C in an insulated cup. %3D (ii) Which liquid, water or methanol, would be more effective as a cooling agent for hot metal? That is, which liquid would require less mass to achieve the same amount of cooling? Justify your answer in terms of the quantity of heat required and/or the definition of specific heat capacity. A student wishes to make a solution of potassium hydroxide, (KOH, M=56.11 g/mol) in methanol, a measure the enthalpy of dissolution of the solid. The student weighs out 4.00 g of KOH(s) and 100.0 of CH,OH(e), carefully adds the KOH to the CH,OH in an insulated cup with stirring, and measures : temperature rise of 12.0 Celsius degrees. (d) Calculate the enthalpy change in kJ/mol for the dissolution reaction of KOH(s) in CH,OH(8) described above and represented below. Assume the specific heat capacity of the final solution is 2.23 J gl °C-. Express your answer with the correct sign and units. KOH(s) → K*(in CH,OH) + OH-(in CH,OH) (e) Calculate the molarity of the KOH(in CH,OH) solution made in part (d) above. Assume the density of the final solution is 0.795 g/mL. Unau
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