151.

Compute internal energy change of a system if it
(i) absorbs 500 kJ heat and does 300 kJ work.

(ii) loses 200 kJ heat and has 450 kJ of work done on it.

152. In a process, 701 J of heat is absorbed by a system and 394 J of work is done by the system. What is the change in internal energy for the process?

153.

A sample of gas is compressed by an average pressure of 0.50 bar so as to decrease its volume from 450 cm³ to 250 cm³. During the process 6.00 J of heat flows out to surroundings. Calculate the change in internal energy of the system.

154.

State whether each of the following will increase or decrease the total energy content of the system:
(i) heat transferred to the surroundings
(ii) work done on the system
(iii) work done by the system.

155. Express the change in internal energy of a system when:

(i) No heat is absorbed by the system from the surroundings, but work (w) is done on the system. What type of wall does the system have?

(ii) No work is done on the system, but q amount of heat is taken out from the system and given to the surroundings. What type of wall does the system have?

(iii) w amount of work is done by the system and q amount of heat is supplied to the system. What type of system would it be?

156. Explain the terms enthalpy and enthalpy change.

157. Derive a relationship between ∆H and ∆U.

158. Show that the change in enthalpy at constant pressure for a reaction involving gases is given by the expression.

159.

Under what conditions
(i)∆H < ∆U
(ii) ∆H > ∆U
(iii) ∆H = ∆U?

160. What becomes of the energy supplied to water molecules as they are heated in a closed container from 298K to 308K?