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dimaraw [331]
3 years ago
13

Calculate the energy for vacancy formation in silver, given that the equilibrium number of vacancies at 800˚C (1073 K) is 3.6 ×

1023 m-3 . The atomic weight and density (at 800˚C) for silver are, respectively, 107.9 g/mol and 9.5 g/cm3 .
Chemistry
2 answers:
____ [38]3 years ago
5 0

Answer:

The energy for vacancy formation in silver is 1.1 ev/atom

Explanation:

The total number of sites is equal to:

N=\frac{N_{A} \rho }{A}

Where

NA = Avogadro´s number = 6.023x10²³atom/mol

A = atomic weight of silver = 107.9 g/mol

ρ = density of silver = 9.5 g/cm³

Replacing:

N=\frac{6.023x10^{23}*9.5 }{107.9} =5.3x10^{22} atom/cm^{3} =5.3x10^{28} m^{-3}

The energy for vacancy is equal:

Q=-RTln(\frac{N_{v} }{N} )

Where

R = 8.314 J/mol K = 8.614x10⁻⁵ev/atom K

T = 800°C = 1073 K

Nv = number of vacancy = 3.6x10²³m⁻³

Replacing:

Q=-8.614x10^{-5} *1073*ln(\frac{3.6x10^{23} }{5.3x10^{28} } )=1.1ev/atom

krek1111 [17]3 years ago
4 0

Answer : The energy for vacancy formation in silver is, 1.762\times 10^{-19}J

Explanation :

Formula used :

N_v=N\times e^{(\frac{-E}{K\times T})}

or,

N=\frac{N_A\times \rho}{M}

So,

N_v=[\frac{N_A\times \rho}{M}]\times e^{(\frac{-E}{K\times T})}

where,

N_v = equilibrium number of vacancies = 3.6\times 10^{23}m^{-3}=3.6\times 10^{20}L^{-1}

E = energy = ?

M = atomic weight = 107.9 g/mole

N_A = Avogadro's number = 6.022\times 10^{23}mol^{-1}

\rho = density = 9.5g/cm^3=9.5g/ml=9500g/L

T = temperature = 800^oC=273+800=1073K

K = Boltzmann constant = 1.38\times 10^{-23}J/K

Now put all the given values in the above formula, we get:

3.6\times 10^{20}L^{-1}=[\frac{(6.022\times 10^{23}mol^{-1})\times 9500g/L}{107.9g/mol}]\times e^{[\frac{-E}{(1.38\times 10^{-23}J/K)\times 1073K}]}

E=1.762\times 10^{-19}J

Therefore, the energy for vacancy formation in silver is, 1.762\times 10^{-19}J

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A compound contains 6.0 g of carbon and 1.0 g of hydrogen and has a molar mass of 42.0 g/mol.
makvit [3.9K]

Answer:

%C = 85.71 wt%; %H = 14.29 wt%; Empirical Formula => CH₂; Molecular Formula => C₃H₆

Explanation:

%Composition

Wt C = 6 g

Wt H = 1 g

TTL Wt = 6g + 1g = 7g

%C per 100wt = (6/7)100% = 85.71 wt%

%H per 100wt = (1/7)100% = 14.29 wt % or, %H = 100% - %C = 100% - 85.71% = 14.29 wt% H

What you should know when working empirical formula and molecular formula problems.

Empirical Formula=> <u>smallest</u> whole number ratio of elements in a compound

Molecular Formula => <u>actual</u> whole number ratio of elements in a compound

Empirical Formula Weight x Whole Number Multiple = Molecular Weight

From elemental %composition values given (or, determined as above), the empirical formula type problem follows a very repeatable pattern. This is ...

% => grams => moles => ratio => reduce ratio => empirical ratio

for determination of molecular formula one uses the empirical weight - molecular weight relationship above to determine the whole number multiple for the molecular ratios.

Caution => In some 'textbook' empirical formula problems, the empirical ratio may contain a fraction in the amount of 0.25, 0.50 or 0.75. If such an issue arises, multiply all empirical ratio numbers containing 0.25 and/or 0.75 by '4'  to get the empirical ratio and multiply all empirical ration numbers containing 0.50 by '2' to get the final empirical ratio.

This problem:

Empirical Formula:

Using the % per 100wt values in part 'a' ...

              %     =>         grams                 =>                 moles

%C => 85.71% => 85.71 g* / 100 g Cpd => (85.71 / 12) = 7.14 mol C

%H => 14.29% => 14.29 g / 100 g Cpd => (14.29 / 1) = 14.29 mol H

=> Set up mole Ratio and Reduce to Empirical Ratio:

mole ratio C:H =>  7.14 : 14.29

<u>To reduce mole values to the smallest whole number ratio,  divide all mole values by the smaller mole value of the set.</u>

=> 7.14/7.14 : 14.29/7.14 => Empirical Ration=> 1 : 2

∴ Empirical Formula => CH₂

Molecular Formula:

(Empirical Formula Wt)·N = Molecular Wt => N = Molecular Wt / Empirical Wt

N = 42 / 14 = 3 => multiply subscripts of empirical formula by '3'.

Therefore, the molecular formula is C₃H₆

3 0
3 years ago
Pleaseeeeeefgghhbbbbbbbbbb
ehidna [41]
<h2>Hey There!</h2><h2>_____________________________________</h2><h2>Answer:</h2><h2>----------------------------------------------------------------------</h2><h2>ELECTROPLATING </h2>

Electroplating the plating one metal on to the another metal, It is mostly used for preventing corrosion by using copper or chromium or decorate the object by using gold or silver plating.

__________________________________________________________

<h3>Principle:</h3>

When electricity is passed the thin layer of metal is deposited on another metal and water molecule given out as a By-Product, Thus this process works on the principle of Hydrolysis.

<h2>_____________________________________</h2><h2>QUESTION:</h2>

A) Electrolysis

B) Chromium prevents corrosion and gives the fine shining touch to the objects.

C) The metal which is deposited to the object i.e. spoon will be connected to the positive electrode of a battery, Thus it is anode. The spoon at which electroplating is need to be done is connected to the negative electrode, thus the Spoon is cathode.

<h2>_____________________________________</h2><h2>Best Regards,</h2><h2>'Borz'</h2>

5 0
3 years ago
Which of the following will reduce copper?<br> zinc<br> mercury<br> fluorine<br> chlorine
laiz [17]
Zinc because the only metals that would be able to reduce copper ions in solution would be hydrogen, lead, tin, nickel, iron, zinc, aluminum, Magnesium, sodium, calcium, potassium, and lithium. and according to your answer choices Zinc is the answer.
4 0
3 years ago
Read 2 more answers
Which is the best reason for choosing the beaker for heating the solution? The beaker is the only container that can withstand h
lyudmila [28]

Answer: The beaker will not tip over when placed on the hot plate


Justification:


Since beakers have flat surface bottoms (usually and this is the condition to use them for this particular application) they can be placed safely on the hot plate without the risk that the they tip over.


Beakers are wide mouth cylindrical vessels used in laboratories to store, mix and heat liquids. Most are made of glass, in which case the glass is resistant to the flame and does not break when exposed to high temperatures or when is heated by direct contact on a hot plate.


So, their safe shape (flat bottom) that makes them stable, along with their ability to withstand high temperatures, make them suitable to heat solutions in laboratories.



6 0
3 years ago
Read 2 more answers
The ka of hypochlorous acid (hclo) is 3.0 ⋅ 10−8 at 25.0 °c. calculate the ph of a 0.0375m hypochlorous acid solution.
Scrat [10]
We can set up an ICE table for the reaction:                      
                      HClO          H+     ClO-
Initial              0.0375       0        0
Change         -x               +x      +x
Equilibrium    0.0375-x     x        x

We calculate [H+] from Ka:     
     Ka = 3.0x10^-8 = [H+][ClO-]/[HClO] = (x)(x)/(0.0375-x)

Approximating that x is negligible compared to 0.0375 simplifies the equation to         
     3.0x10^-8 = (x)(x)/0.0375     
     3.0x10^-8 = x2/0.0375     
     x2 = (3.0x10^-8)(0.0375) = 1.125x10^-9     
     x = sqrt(1.125x10^-9) = 0.0000335 = 3.35x10^-5 = [H+]
in which 0.0000335 is indeed negligible compared to 0.0375.

We can now calculate pH:     
     pH = -log [H+] = - log (3.35 x 10^-5) = 4.47
6 0
3 years ago
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