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3 years ago

15

A refigerator is designed to remove 3 kW from the cold space at -10C while it rejects heat to the kitchen at 25 C. The rate of t

he reversible work is:______

1 answer:

Stells [14]3 years ago

7 0

Answer:

b

Explanation:

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How many photons will be required to raise the temperature of 1.8 g of water by 2.5 k ?'?

tatyana61 [14]

Missing part in the text of the problem:
"<span>Water is exposed to infrared radiation of wavelength 3.0×10^−6 m"</span>

First we can calculate the amount of energy needed to raise the temperature of the water, which is given by
$Q=m C_s \Delta T$
where
m=1.8 g is the mass of the water
$C_s = 4.18 J/(g K)$ is the specific heat capacity of the water
$\Delta T=2.5 K$ is the increase in temperature.

Substituting the data, we find
$Q=(1.8 g)(4.18 J/(gK))(2.5 K)=18.8 J=E$

We know that each photon carries an energy of
$E_1 = hf$
where h is the Planck constant and f the frequency of the photon. Using the wavelength, we can find the photon frequency:
$\lambda = \frac{c}{f}= \frac{3 \cdot 10^8 m/s}{3 \cdot 10^{-6} m}=1 \cdot 10^{14}Hz$

So, the energy of a single photon of this frequency is
$E_1 = hf =(6.6 \cdot 10^{-34} J)(1 \cdot 10^{14} Hz)=6.6 \cdot 10^{-20} J$

and the number of photons needed is the total energy needed divided by the energy of a single photon:
$N= \frac{E}{E_1}= \frac{18.8 J}{6.6 \cdot 10^{-20} J} =2.84 \cdot 10^{20} photons$

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3 years ago

The table below shows the average wind speeds of four hurricanes in Florida. Florida Hurricanes Hurricane | Average Wind Speed (

Anna [14]

Answer:d

Explanation:

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3 years ago

Read 2 more answers

What is the answer to this question number 2?

anzhelika [568]

Answer:

1⁺ ion

Explanation:

Metals in the first group on the periodic table will prefer to form 1⁺ ion. This is because the 1 valence electron in their orbital.

Most metals are electropositive and would prefer to lose electrons than to gain it.

Like all metals, the group 1 elements called the alkali metals would prefer to lose and electron.

On losing an electron the number of protons is then greater than the number of electrons. This leaves a net positive charge.

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2 years ago

Faiyez wrote the problem below

Ilya [14]

445/100 - 5/4 = 445/100 - 125/100 = 320/100 = 16/5 = 3 1/5.

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3 years ago

What do we mean when we say that energy levels are quantized in atoms?

jek_recluse [69]

Answer:

Electrons are located in specific orbit corresponding to discrete energy levels

Explanation:

In Bohr's model of the atom, electron orbit the nucleus in specific levels, each of them corresponding to a specific energy. The electrons cannot be located in the space between two levels: this means that only some values of energy are possible for the electrons, so the energy levels are quantized.

A confirmation of Bohr's model is found in the spectrum of emission of gases. In fact, when an electron jumps from a higher energy level to a lower energy level, it emits a photon whose energy is exactly equal to the difference in energy between the two levels: since the energy levels are discrete, this means that the emitted photons cannot have any value of wavelength, but also their wavelength will appear as a discrete spectrum. This is exactly what it is observed in the spectrum of emission of gases.

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2 years ago