How many grams of lithium are in 6.02*10^21 atoms

Do metals gain or lose electrons as they form ions

Anna71 [15]

Answer:

They usually lose electrons to form ions with 2 positive charges

Explanation:

6 0

2 years ago

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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

2 years ago

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(b) What is the pH of 0.40 M triethylammonium chloride, CH₃ (CH₂)₃ NHCl ?

Valentin [98]

pH of 0.40M triethylammonium chloride is 5.90.

A solution's acidity may be determined by looking at its pH, which is a measurement of hydrogen ion concentration. Pure water slightly separates into ions with roughly equal amounts of hydrogen and hydroxyl (OH) ions. [H+] is 107 for a neutral solution, or pH = 7.

<h3>Given : </h3>

Concentration of triethylammonium chloride = 0.40M

pH = ?

<h3>Solution: </h3>

(CH3CH2)3NHCl ------> (CH3CH2)3NH⁺ + Cl⁻

(CH3CH2)3NH⁺ will react with water to give H3O⁺ .

(CH3CH2)3N will have a Kb = 5.2 x 10 ^(-4)

Kw = Kb x Ka

=> Ka = Kw / Kb = 10^(-14) / 5.2 x 10 ^(-4)

=> Ka = 1.92 x 10^(-11)

so by the reaction we have ,

Ka = x²/(0.40 - x)

=> x = 1.2393 x 10 ^(-6)

now, pH = -log( [H3O⁺]) = - log ( 1.2393 x 10 ^(-6)) = 5.906

To learn more about pH :

brainly.com/question/15289741

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5 0

5 months ago

Genetic equilibrium is the state in which allele frequencies do<br> not change in a<br> Check it

Vikentia [17]

Answer:

Genetic equilibrium is the state in which allele frequencies do

not change in a generation over generation.

Explanation:

Genetic equilibrium can be described as a situation which arises when a certain allele or genotype remains constant for a species generation over generations. Genetic equilibrium can be maintained if no external factors like mutations affect the population of the species. The phenomenon of natural selection and evolution need to be stopped if a genetic equilibrium is to be maintained. Hardy-Weinberg theorem is the mathematical depiction of genetic equilibrium.

3 0

2 years ago

What could you do if you wanted to slow down the rate of a particular reaction?

hjlf

Answer:

catalyst

Explanation:

this help toalter or speed up the rate of reaction could be the most to slow it

5 0

1 year ago