A person sitting in a chair with wheels stands up, causing the chair to roll backward across the floor. The momentum of the chair a. was zero while stationary and increased when the person stood.

b. was greatest while the person sat in the chair.

c. remained the same.

d. was zero when the person got out of the chair and increased while the person sat.

8.29 two streams containing pyridine and acetic acid at 25°c are mixed and fed into a heat exchanger. due to the heat-of-mixing effect, it is desired to reduce the temperature after mixing to 25°c using a stream of chilled ethylene glycol as indicated in the diagram. calculate the mass flow rate of ethylene glycol needed. the heat capacity of ethylene glycol at these conditions is approximately 2.8 kj/(kg k), and the enthalpy change of mixing (δmixh) is given below.