An air conditioner operating between $\mathbf{93}\mathbf{°}\mathbf{F}$and $\mathbf{70}\mathbf{°}\mathbf{F}$ is rated at $\mathbf{4000}\mathbf{Btu}\mathbf{/}\mathbf{h}$ cooling capacity. Its coefficient of performance is $\mathbf{27}\mathbf{\%}$ of that of a Carnot refrigerator operating between the same two temperatures. What horsepower is required of the air conditioner motor?

(a)Find the energy absorbed as heat and (b) Find the change in entropy of a 2.00 kg block of copper whose temperature is increased reversibly from $\mathbf{25}\mathbf{.}\mathbf{0}\mathbf{°}\mathit{C}$ to role="math" localid="1661323309034" $\mathbf{100}\mathbf{°}\mathit{C}$. The specific heat of copper is 386 J/kgK.

A 45.0 g block of tungsten at $\mathbf{30}\mathbf{.}\mathbf{0}\mathbf{°}\mathbf{C}$ and a 25.0 g block of silver at $\mathbf{-}\mathbf{120}\mathbf{.}\mathbf{0}\mathbf{°}\mathbf{C}$ are placed together in an insulated container. (See Table 18-3 for specific heats.) (a) What is the equilibrium temperature? What entropy changes do (b) the tungsten, (c) the silver, and (d) the tungsten–silver system undergo in reaching the equilibrium temperature?

An inventor claims to have invented four engines, each of which operates between constant-temperature reservoirs at 400 and 300K. Data on each engine, per cycle of operation, are: engine A, ${\mathbf{Q}}_{\mathbf{H}}\mathbf{=}\mathbf{200}\mathbf{J}\mathbf{,}\mathbf{}{\mathbf{Q}}_{\mathbf{L}}\mathbf{=}\mathbf{175}\mathbf{J}$, and W = 40 J; engine B, ${\mathbf{Q}}_{\mathbf{H}}\mathbf{=}\mathbf{500}\mathbf{J}\mathbf{,}\mathbf{}{\mathbf{Q}}_{\mathbf{L}}\mathbf{=}\mathbf{-}\mathbf{200}\mathbf{}\mathbf{J}$,and W = 400 J; engine C, ${\mathbf{Q}}_{\mathbf{H}}\mathbf{=}\mathbf{600}\mathbf{J}\mathbf{,}\mathbf{}{\mathbf{Q}}_{\mathbf{L}}\mathbf{=}\mathbf{-}\mathbf{200}\mathbf{J}$, and W = 400 J; engine D, ${\mathbf{Q}}_{\mathbf{H}}\mathbf{=}\mathbf{100}\mathbf{J}\mathbf{,}{\mathbf{Q}}_{\mathbf{L}}\mathbf{=}\mathbf{-}\mathbf{90}\mathbf{J}$, and W = 10J. Of the first and second laws of thermodynamics, which (if either) does each engine violate?

The efficiency of a particular car engine is 25% when the engine does 8.2 KJ of work per cycle. Assume the process is reversible. (a) What is the energy the engine gains per cycle as heat ${\mathit{Q}}_{\mathbf{g}\mathbf{a}\mathbf{i}\mathbf{n}}$ from the fuel combustion and (b)What is the energy the engine loses per cycle as heat ${\mathit{Q}}_{\mathbf{l}\mathbf{o}\mathbf{s}\mathbf{t}}$ If a tune-up increases the efficiency to 31%.(c) What i and (d) What is ${\mathit{Q}}_{\mathbf{lost}}$ at the same work value?

A box contains 100 atoms in a configuration that has 50 atoms in each half of the box. Suppose that you could count the different microstates associated with this configuration at the rate of 100 billion states per second, using a supercomputer. Without written calculation, guess how much computing time you would need: a day, a year, or much more than a year.