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Leto [7]
3 years ago
13

If the molecular weight of a semiconductor is 27.9 grams/mole and the diamond lattice constant is 0.503 nm, what is the density

of the semiconductor in grams/cc ? Two significant digits, fixed point notation.
Chemistry
1 answer:
adelina 88 [10]3 years ago
4 0

Explanation:

The given data is as follows.

      Mass = 27.9 g/mol

As we know that according to Avogadro's number there are 6.023 \times 10^{26} atom present in 1 mole. Therefore, weight of 1 atom will be as follows.

            1 atoms weight = \frac{38}{6.023 \times 10^{26}}    

In a diamond cubic cell, the number of atoms are 8. So, n = 8 for diamond cubic cell.

Therefore, total weight of atoms in a unit cell will be as follows.

            = \frac{8 \times 27.9 g/mol}{6.023 \times 10^{26}}

            = 37.06 \times 10^{-26}

Now, we will calculate the volume of a lattice with lattice constant 'a' (cubic diamond) as follows.

                   = a^{3}

                   = (0.503 \times 10^{-9})^{3}

                   = 0.127 \times 10^{-27} m^{3}

Formula to calculate density of diamond cell is as follows.

               Density = \frac{mass}{volume}

                             = \frac{37.06 \times 10^{-26}}{0.127 \times 10^{-27} m^{3}}

                            = 2918.1 g/m^{3}

or,                         = 0.0029 g/cc       (as 1 m^{3} = 10^{6} cm^{3})

Thus, we can conclude that density of given semiconductor in grams/cc is 0.0029 g/cc.

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Answer:

b) 7

Explanation:

The pH of a solution produced by the neutralization reaction between 1M of H₂SO₄ and KOH with 1M is closest to 7.

pH is a standard for measuring the acidity and alkalinity of a solution. A solution that is acidic will have a pH less than 7, a neutral solution will have pH of 7 and a basic solution will have pH greater than 7.

What is a neutralization reaction?

  • It is an acid-base reaction in which hydrogen and hydroxide ions combines to form water.
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In this reaction a base simply neutralizes an acid and the solution becomes neutral before it goes into completion.

Therefore, a neutral solution will have pH of 7 or close to it.

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3 years ago
The velocity (speed) of an object was determined to be 45 miles per
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Answer: 72.58 km/hr

Explanation:

\frac{45 miles}{1 hour}×\frac{1 km}{0.62 miles} = 72.58 km/hr

4 0
2 years ago
Read 2 more answers
Identify the units used to measure volume mass.
Strike441 [17]

Answer:

The metric system uses units such as meter, liter, and gram to measure length, liquid volume, and mass, just as the U.S. customary system uses feet, quarts, and ounces to measure these.

Volume: 1 liter is a little more than 1 quart

Mass: 1 kilogram is a little more than 2 pounds

Length: 1 centimeter is a little less than half an

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2 years ago
The energy of a pendulum is recorded at different positions in the table below. Use the data in the table to determine the amoun
natta225 [31]

Answer:

36.55 J

Explanation:

PE = Potential energy

KE = Kinetic energy

TE = Total energy

The following data were obtained from the question:

Position >> PE >>>>> KE >>>>>> TE

1 >>>>>>>> 72.26 >> 27.74 >>>> 100

2 >>>>>>>> 63.45 >> x >>>>>>>> 100

3 >>>>>>>> 58.09 >> 41.91 >>>>> 100

The kinetic energy of the pendulum at position 2 can be obtained as follow:

From the table above, at position 2,

Potential energy (PE) = 63.45 J

Kinetic energy (KE) = unknown = x

Total energy (TE) = 100 J

TE = PE + KE

100 = 63.45 + x

Collect like terms

100 – 63.45 = x

x = 36.55 J

Thus, the kinetic energy of the pendulum at position 2 is 36.55 J.

7 0
2 years ago
Heat is transferred by conduction through a wall of thickness 0.87 m. What is the rate of heat transfer if the walls thermal con
erik [133]

Explanation:

The given data is as follows.

         Thickness (dx) = 0.87 m,       thermal conductivity (k) = 13 W/m-K

        Surface area (A) = 5 m^{2},       T_{1} = 14^{o}C

        T_{2} = 93^{o}C

According to Fourier's law,

                    Q = -kA \frac{dT}{dx}

Hence, putting the given values into the above formula as follows.

                      Q = -kA \frac{dT}{dx}

                          = -13 W/m-k \times 5 m^{2} \times \frac{(14 - 93)}{0.87 m}

                          = 5902.298 W

Therefore, we can conclude that the rate of heat transfer is 5902.298 W.

4 0
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