Question

5. For a particular process, q=-17 kJ and w = 21 kJ. Which of the following statements is false? a. Heat flows from the system to the surroundings. b. The system does work on the surroundings. c. AE = +4 kJ d. The process is exothermic. e. None of the above is false.

Answer 1

As per the first law of thermodynamics

LE=q+w

where q=heat flow from or into the system

When q is positive, heat flows into the system, when q is negative heat flows from the system.

w=work flow from or into the system

When w is positive, work is done on the system, when w is negative work is done by the system.

$\Delta E$=total internal energy change of the system=q+w=-17 kJ+21 kJ=+4 kJ so statement c. is true.

Here q=-17 kJ and since it is a negative quantity so this is an exothermic process i.e. there is an overall release of heat from the system into the surroundings. So statement d. is true.

This means that heat flows from the system into the surrounding as q has a negative sign. So statement a. is correct.

Now w is a positive quantity which means work is done onto the system. So statement b is false.

As statement b. is false so statement e is false.