# chemistry

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Calculate the change in internal energy for a system that absorbs 242 J of heat and does 193 J of work on the surroundings...

• chemistry -

internal energy, U, is the sum heat, Q, and work, W:
U = Q + W
U = 242 - 193
U = + 49 J

>>>sign conventions for U = Q + W:
*heat absorbed by the system is (+)
*heat released by the system is (-)
*work done BY the system is (-)
*work done ON the system is (+)
*work done BY the surroundings is (+)
*work done ON the surroundings is (-)

but note that in some books the formula for internal energy is U = Q - W

so there,, :)

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