Question

1a) A gaseous system absorbs 97 J of heat and increases its internal energy by 85 J. Which of the following statements is correct? The volume of the system decreases and a positive amount of work is done. The volume of the system increases and a positive amount of work is done. The volume of the system increases and a negative amount of work is done. The volume of the system remains constant and no work is done The volume of the system decreases and a negative amount of work is done. 1b)A 27.1-g piece of iron initially at 92.9 °C is submerged into 194.4 g of water at 18.1 °C. What is the final temperature of the metal once the metal and water reaches thermal equilibrium? The specific heats of iron and water are 0.449 J/g·°C and 4.18 J/g·°C, respectively.

Answer 1

1a) Δq =+97 J
     ΔU = +85J
   ΔU = Δq + W , W =P ΔV = 85-97 = -12 J of work is done

The volume of the system increases and negative amount of work is done

1b) q _lost = q_gain , (mc_pΔt)_iron = (mc_pΔt)_water
   27.1 * (92.9 - x) * 0.449 = 194.4 * (x- 18.1) * 4.18
   12.1679 ( 92.9 - x) = 812.592 (x- 18.1)
   1130.3971 - 12.1679x = 812.592x - 14707.9152
15838.3123 = 824.7599 x
   x = 19.2035
The final temperature of the metal once the metal reaches thermal equilibrium is 19.2 ^oC