Part 1-

1. Describe what happens when two substances at different temperatures come into contact. Describe how the law of conservation of energy applies to this system.

2. You used a calorimeter in the Heat Transfer lab. Explain how the calorimeter works, and how you can calculate the heat given off or absorbed by the reaction being studied.

3. A calorimeter contains 500 g of water at 25°C. You place a hand warmer containing 100 g of liquid sodium acetate (NaAC) inside the calorimeter. When the sodium acetate finishes crystallizing, the temperature of the water inside the calorimeter is 32.2°C. The specific heat of water is 4.18 J/g-°C. What is the enthalpy of fusion (ΔH_f) of the sodium acetate? Show your work.

Part 2-

1. Explain what is in a buffer. Discuss the function of a buffer. How will pH change when small amounts of acids or bases are added to the buffer solution?

2. Cooks use baking soda to make cakes light and fluffy. You might have used baking soda yourself. Baking soda is NaHCO₃. A 0.1 M solution of baking soda in water has a [H⁺] of about 4.0 × 10^-9. (You may prefer to think of the hydronium ion concentration, [H₃O⁺], as 4.0 × 10^-9.) Write the formula for the calculation of pH, and then show each step as you calculate the pH of a 0.1 M solution of baking soda.

3. Before tackling this problem, be sure you know how to find the antilog of a number using a scientific calculator.

A solution has a pH of 5.4. Write the formula you will use to calculate the [H⁺] and then show all your work leading to the determination of [H⁺].

Part 3-

1. What is Charles's law? 

• State the definition of the law in words.
• What are the assumptions of Charles's law?
• Write mathematical equations that represent the law.
• What can you do with Charles's law?
• Using a gas-filled balloon as an example, describe what happens to the gas molecules that behave according to Charles's law.

2. Draw a structural formula for 3,4-hexene (C₆H₁₂), which has a double bond between the number 3 and 4 carbons in the chain. What class of compound is it, and what feature distinguishes it as that class?

3. Besides the major types of radioactive decay, there are two others: positron emission and electron capture.

• Compare and contrast positrons with electrons.
• Explain how positron emission works and how it causes transmutations.
• Explain how electron capture works and how it causes transmutations.
• Compare the transmutations caused by positron emissions and electron capture.

4. A calorimeter contains 500 g of water at 25°C. You place a hand warmer containing 200 g of liquid sodium acetate inside the calorimeter. When the sodium acetate finishes crystallizing, the temperature of the water inside the calorimeter is 39.4°C. The specific heat of water is 4.18 J/g-°C. What is the enthalpy of fusion (DH_f) of the sodium acetate? (Show your work.) Where necessary, use q = mH_f.