A system expands by 0.91m3 at a constant pressure

of 105 kPa.

(a) Find the heat that flows into or out of

thesystem if its internal energy increases by 91 J.

(b) Find the heat that flows into or out of the system if

itsinternal energy decreases by 1950J.

a) Q = 95.641 KJ

The heat will flow into the system.

b) Q = 93.600 KJ

The heat will flow into the system.

Explanation:

Given that

ΔV = 0.91 m³

P = 105 KPa

From first law of thermodynamics

Q = ΔU + W

Q = ΔU + P ΔV

ΔU=Change in the internal energy

PΔV = Work done

Q=Heat transfer

a)

Q = ΔU + P ΔV

Given that ΔU = 91 J

Q = 91 + 0.91 x 105 x 1000 J

Q = 95641 J

Q = 95.641 KJ

The heat will flow into the system.

b)

Given that ΔU = - 1950 J

Q = - 1950 J + 0.91 x 105 x 1000 J

Q = 93600 J

Q = 93.600 KJ

The heat will flow into the system.

Note - If the Q comes negative then it means that heat will flow out of the system.