Question

1)A gas is allowed to expand, at constant temperature, from a volume of 1.0 L to 10.1 L against an external pressure of 0.50 atm. If the gas absorbs 250 J of heat from the surroundings, what is the change in energy of the gas in J?

2)What is the energy in joules of one photon of microwave
radiation with a wavelength 0.122 m? (c = 2.9979 10^{8}
m/s; h = 6.626 10^{–34} Js)

3) What element is reduced in the following chemical reaction?

Cu + 2H_{2}SO_{4} ®CuSO_{4} +
SO_{2} + 2H_{2}O

Plz explain....

Answer #1

1)

W = -Pext(Vf-Vi)

P = 0.5 atm

Vi = 1.0 L

Vf = 10.1 L

put values in above expression

W = -Pext(Vf-Vi)

= -0.5 atm (10.1L - 1.0L)

= -4.55 atm.L

= -4.55 *101.33 J

= -461.0515 J

Q = 250 J (positive because heat is absorbed)

W = -461.0515 J

we have below equation to be used:

deltaU = Q + W

deltaU = (250.0 J) + (-461.0515 J)

deltaU = -211 J

Answer: -211 J

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