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irinina [24]
2 years ago
7

Plz help me it a timed test

Chemistry
1 answer:
Shtirlitz [24]2 years ago
6 0

Answer:

B

Explanation:

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What is one takeaway you have about future sea levels rising ?
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Answer:

Our world will never be the same. Our beaches will be submerged, many towns, cities, states, and even countries will be partially if not completely submerged. All these human cities being flooded will kill thousands of people, pollute the ocean, and lose billions of dollars.

Explanation:

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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.

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3 years ago
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The only part of Earth's inner structure that is a liquid is the _____. A. inner core B. lower mantle C. outer core D. crust
slavikrds [6]

Answer:

lower mantle

Explanation:

because the core and the crust are solid.

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3 years ago
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Please help me, I really need it, God Bless you <3
gladu [14]

#1

\\ \sf\longmapsto {}^{88}_{38}Sr^{2+}

  • As 2 electrons are donated Hence the No of electrons =38-2=36

#2

\\ \sf\longmapsto {}^{51}_{23}V^{3+}

  • As 3 electrons donated the no of electrons=23-3=20

#3

\\ \sf\longmapsto {}^{55}_{26}Fe^{3+}

  • No of neutrons=55-26=29

#4

\\ \sf\longmapsto {}^{112}_{48}

  • As 2 electrons are donated no of electrons =48-2=46

#5

\\ \sf\longmapsto {}^{210}_{82}Pb^{2+}

  • No of neutrons=210-82=128
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What does the 3 indicate in 1s22s22p63s1?
Dahasolnce [82]
The 3 indicates the third electron shell. (Which has only 1 electron in it in this configuration)

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