CH 102 Spring 2026 – Discussion Worksheet 1 Name: ________________________________________
1. The following problem is deceptively difficult: “A total of 15 kJ of energy are added to a 22.0 gram ice cube initially at
–7.5 °C. What is the final temperature of the water?” Do not answer the question just yet! Let’s investigate carefully.
a. In words (don’t solve the problem), what happens when you add the 15 kJ of energy to the ice cube initially at
–7.5 °C? This is not a simple question. How many different steps/processes are potentially involved in this
problem?
b. What thermodynamic quantities would you need to solve this problem?
c. Write any relevant chemical reaction equations associated with this problem.
d. Write symbolically, but do not solve, an expression to solve this problem.
2. [McQuarrie 15–11] Heat was added to 25.0 grams of solid sodium chloride, NaCl(s), at the rate of 3.00 kJ/min. The
temperature remained constant at 800.7 °C, the normal melting point of NaCl(s), for 241 seconds. Calculate the molar
enthalpy of fusion of NaCl(s).
3. [McQuarrie 15–5] The metal gallium melts when held in the hand; its melting point is 29.76 °C. How much energy (in
kJ) as heat is removed from the hand when 5.00 grams of gallium initially at 20.0 °C melts? The value of ∆𝐻!"# is
5.576 kJ/mol and the specific heat of gallium is 0.374 J⋅g–1K–1. Take the final temperature to be 29.76 °C.
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1. The following problem is deceptively difficult: “A total of 15 kJ of energy are added to a 22.0 gram ice cube initially at
–7.5 °C. What is the final temperature of the water?” Do not answer the question just yet! Let’s investigate carefully.
a. In words (don’t solve the problem), what happens when you add the 15 kJ of energy to the ice cube initially at
–7.5 °C? This is not a simple question. How many different steps/processes are potentially involved in this
problem?
b. What thermodynamic quantities would you need to solve this problem?
c. Write any relevant chemical reaction equations associated with this problem.
d. Write symbolically, but do not solve, an expression to solve this problem.
2. [McQuarrie 15–11] Heat was added to 25.0 grams of solid sodium chloride, NaCl(s), at the rate of 3.00 kJ/min. The
temperature remained constant at 800.7 °C, the normal melting point of NaCl(s), for 241 seconds. Calculate the molar
enthalpy of fusion of NaCl(s).
3. [McQuarrie 15–5] The metal gallium melts when held in the hand; its melting point is 29.76 °C. How much energy (in
kJ) as heat is removed from the hand when 5.00 grams of gallium initially at 20.0 °C melts? The value of ∆𝐻!"# is
5.576 kJ/mol and the specific heat of gallium is 0.374 J⋅g–1K–1. Take the final temperature to be 29.76 °C.
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