Question

A mixture of gaseous reactants is put into a cylinder, where a chemical reaction turns them into gaseous products. The cylinder has a piston that moves in or out, as necessary, to keep a constant pressure on the mixture of 1atm. The cylinder is also submerged in a large insulated water bath. (See sketch at right.) The temperature of the water bath is monitored, and it is determined from this data that 108.kJ of heat flows out of the system during the reaction. The position of the piston is also monitored, and it is determined from this data that the system does 179.kJ of work on the piston during the reaction.

Answer 1

Complete Question

The diagram for this question is shown on the first uploaded image

The question to solve is shown on the second uploaded image

Answer:

1. The reaction is exothermic
2. The temperature of the water bath goes up
3. The piston move out
4. The system release energy
5. The amount of energy released is
   `\Delta E = - 287kJ`

Step-by-step explanation:

From the question we are told that

The pressure is
`P = 1 atm`

The amount of heat flow out of the system is
`q = - 108 \ kJ`

The workdone by the system is
`w = - 179 \ kJ`

The first question is to state whether the reaction is exothermic

Yes this reaction is exothermic because heat is being transferred out of the system

The second second question is to determine whether the temperature of the water goes up or down

The temperature of the water goes up because above we see that the reaction is exothermic which means that heat is being transferred from the system to the surrounding which i the water bath in this case so this then implies that the temperature of the water in the water bath would go up

The third question is to determine whether the piston moves in or out

Now since work is done by the system which would mean that its pressure would increase but we require a constant pressure of 1 atm and to achieve this the there is need for an increase in volume in order to return the pressure back to 1 atm and this can be achieved by the piston moving out

The fourth question is to determine whether this reaction releases or absorbs energy

We can determine this by looking at the first law of thermodynamics

which is stated mathematically as

`\Delta E = q + w`

Where w is the workdone by the system given in the question as (-179 kJ)

`\Delta E` is the internal energy

q is the heat flowing out of the system which is given as (-108 kJ)

Substituting this into the question we have that

`\Delta E = -108 -179`

`\Delta E = - 287kJ`

This negative internal energy indicates that energy is been released from the system.

The fifth ask that we determine how much energy is been absorbed or released by the system

The solution is already obtained in the fourth question an it is

`\Delta E = - 287kJ`

When to understand that heat flow into a system mean that the system

gains energy in form of heat so that energy with respect to the system is positive

Also When heat i transferred out of a system it means that the system losses energy in form of heat so that energy in term of the system is negative

Note also that when an external body does work on a system that the workdone is done is positive

But when a system does work on an external body the workdone is negative

In the case of Internal energy

When energy is absorbed by a system the then that energy in terms of the system is positive

But when energy is released by the system to the surrounding then that energy is negative with respect to the system