A salt is dissolved in a glass beaker containing 100 mL of water at room tempera

Question

A salt is dissolved in a glass beaker containing 100 mL of water at room temperature. The temperature of the resulting solution is higher than room temperature. Define the boundaries of the system. Are the boundaries diathermic or adiabatic? Is the system open, closed or isolated? Is energy exchanged between the system and the surroundings during the solution process? If so, is it work or heat? If it is work, is it done by or on the system? If it is heat, is the process endothermic or exothermic? Is the system losing or gaining energy during the process? A non reusable cold pack consists of the sealed pouch (containing ammonium salt) which is inside a bigger pouch filled with water. Squeezing the outer pouch causes the inner pouch to break and salt to dissolve in the water. The solution process is endothermic. Take the boundaries of the system to be the outer pouch. Are the boundaries diathermic or adiabatic? Is the system open, closed or isolated? Is energy exchanged between the system and the surroundings during the solution process? If so, is it work or heat? If it is work, is it done by or on the system? Is the system losing or gaining energy during the process? In your own words, define the concepts of heat and work in terms of molecular motion. By which mechanism do you think molecules in hot surroundings stimulate molecules in a cooler system to move vigorously? List the advantages of considering each of the following in calculating the work done by an expanding gas on such a piston. a massless piston a frictionless piston a rigid piston a perfectly fitting piston

Explanation / Answer

7. The hotter an object is, the faster the motion of the molecules inside it. Thus, the heat of an object is the total energy of all the molecular motions inside the object while temperature, is a measure of the average heat or thermal energy of the molecules in a substance.

8. The hotter molecules on collision with cooler molecules transfer the heat energy to them and stimulate them to move faster.

9. If a massless piston, work done------> change in volume, work done =0

a friction less piston -----> change in volume, work done =0

a rigid piston ------> increase in volume = work done

a perfectly fitting piston -----> increase in volume = work done

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.