The internal energy of a substance is a state function. What does it mean? An id

Question

The internal energy of a substance is a state function. What does it mean? An ideal gas expands isothermally (at a constant temperature). The internal energy of an ideal gas remains constant during an isothermal change. If q is 76 J what are Delta E and w? Microwaves have frequencies in the range of 10^9 to 10^12/s (cycles per second), equivalent to between 1 gigahertz and 1 terahertz. What is the wavelength of a microwave radiation whose frequency is 1.395 times 10^10/s? Calculate the wavelength of the Balmer line of the hydrogen spectrum in which the initial n quantum number is 3 and the final n quantum number is 2. Write the ground-state electronic configuration for the following: Ne^2+, s^-2, and Li

Explanation / Answer

(7)

(A) State function: The propety of the system which depends only on initial and final states of the system but not on the path through whcih the system is reached to final state is called state function.

(B) According to first law of thermodynamics,

delta E = q + w

since the process is isothermal, the temperature remains constant,

so, deltaE = 0

q + w = 0

w = - q

w = -76 J

(8)

frequency = c / lambda

lambda = 3 *108 / 1.395 * 1010

so, wavelength = 2.15 * 10-2 m = 2.15 cm

(b) 1/lambda = 109678[(1/n12)-(1/n22)]

= 109678 [(1/4)-(1/9)

= 15233

Lambda = 6.56 * 10-5 cm

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