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3 years ago

The molar mass of silicon

Chemistry

2 answers:

Yuliya22 [10]3 years ago

7 0

<span>28.0855 u ± 0.0003 u i hopes dis helps you</span>

Norma-Jean [14]3 years ago

4 0

Yes what the guy above me said

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The unit cell for cr2o3 has hexagonal symmetry with lattice parameters a = 0.4961 nm and c = 1.360 nm. If the density of this ma

IRINA_888 [86]

To calculate the packing factor, first calculate the area and volume of unit cell.

Area is calculated as:

$A=6R^{2}\sqrt{3}$

Here, R is radius and is related to a as follows:

$R=\frac{a}{2}$

Putting the value in expression for area,

$A=6(\frac{a}{2})^{2}\sqrt{3}=1.5a^{2}\sqrt{3}$

The value of a is 0.4961 nm

Since, $1 nm=10^{-7}cm$

Thus, $0.4961 nm=4.961\times 10^{-8} cm$

Putting the value,

$Area=1.5(4.961\times 10^{-8}cm)^{2}\sqrt{3}=6.39\times 10^{-15}cm^{2}$

Now, volume can be calculated as follows:

$V=Area\times c$

The value of c is 1.360 nm or $1.360\times 10^{-7} cm$

Putting the value,

$V=(6.39\times 10^{-15}cm^{2})\times (1.360\times 10^{-7} cm)=8.7\times 10^{-22}cm^{3}$

now, number of atom in unit cell can be calculated by using the following formula:

$n=\frac{\rho N_{A}V_{c}}{A}$

Here, A is atomic mass of $Cr_{2}O_{3}$ is 151.99 g/mol.

Putting all the values,

$n=\frac{(5.22 g/cm^{3})(6.023\times 10^{23} mol^{-1})(8.7\times 10^{-22}cm^{3})}{(151.99 g/mol)}\approx 18$

Thus, there will be 18 $Cr_{2}O_{3}$ units in 1 unit cell.

Since, there are 2 Cr atoms and 3 oxygen atoms thus, units of chromium and oxygen will be 2×18=36 and 3×18=54 respectively.

The atomic radii of $Cr^{3+}$ and $O^{2-}$ is 62 pm and 140 pm respectively.

Converting them into cm:

$1 pm=10^{-10}cm$

Thus,

$r_{Cr^{3+}}=6.2\times 10^{-9}cm$

and,

$r_{O^{2-}}=1.4\times 10^{-8}cm$

Volume of sphere will be sum of volume of total number of cations and anions thus,

$V_{S}=V_{Cr^{3+}}+V_{O^{2-}}$

Since, volume of sphere is $V=\frac{4}{3}\pi r^{3}$ ,

$V_{S}=36\left ( \frac{4}{3}\pi (r_{Cr^{3+})^{3}} \right )+54\left ( \frac{4}{3}\pi (r_{O^{2-})^{3}} \right )$

Putting the values,

$V_{S}=36\left ( \frac{4}{3}(3.14) (6.2\times 10^{-9} cm)^{3}} \right )+54\left ( \frac{4}{3}(3.14) (1.4\times 10^{-8} cm)^{3}} \right )=6.6\times 10^{-22}\times 10^{-8}cm^{3}$

The atomic packing factor is ratio of volume of sphere and volume of crystal, thus,

$packing factor=\frac{V_{S}}{V_{C}}=\frac{6.6\times 10^{-22}cm^{3}}{8.7\times 10^{-22}cm^{3}}=0.758$

Thus, atomic packing factor is 0.758.

6 0

3 years ago

Read 2 more answers

What is an example of an electrolyte solution?

Karo-lina-s [1.5K]

Answer:

nacl with water

they are capable of conducting electricity

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3 years ago

Which of the following are functions of the ears?

Advocard [28]

The functions of the ears are:

I. Hearing by collecting and processing sound waves

II. Keeping our balance when we turn or bend over; option A

<h3>What is the function of the ear?</h3>

The ear is one of the five sense organs in the body.

The sense organs are the organs which receive external stimulus and send it to the brain for processing and response.

The other sense organs are:

the eye
the nose
the skin
the tongue

The functions of the ear are for hearing and for balance.

In conclusion, the sense organs function to receive stimulus and send them to the brain.

Learn more about the functions of the ear at: brainly.com/question/924275

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1 year ago

1Which is a dopant for a p-type semiconductor?

aalyn [17]

For a p type of semiconductor we need a dopant which is from 13th group in periodic table

Al , B, Ga, In Tl

So the correct element will be In : Indium

The other elements belongs to 15th group and hence will give n type semiconductor

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3 years ago

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Explain how condensation is invovled in the water cycle

blagie [28]

Condensation is the process of watervapor in the air is changing into liquid water. Condensation is crucial to the water cycle because it is responsible for the formation of clouds. Condensation is also the opposite of evaporation

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3 years ago