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tekilochka [14]
2 years ago
13

Is selenium tetrafluoride an ionic or covalent bond?

Chemistry
1 answer:
nasty-shy [4]2 years ago
4 0

Answer:

Synthesis

The first reported synthesis of selenium tetrafluoride was by Paul Lebeau in 1907, who treated selenium with fluorine:[1]

Se + 2 F2 → SeF4

A synthesis involving more easily handled reagents entails the fluorination of selenium dioxide with sulfur tetrafluoride:[2]

SF4 + SeO2 → SeF4 + SO2

An intermediate in this reaction is seleninyl fluoride (SeOF2).

Other methods of preparation include fluorinating elemental selenium with chlorine trifluoride:

3 Se + 4 ClF3 → 3 SeF4 + 2 Cl2

Structure and bonding

Selenium in SeF4 has an oxidation state of +4. Its shape in the gaseous phase is similar to that of SF4, having a see-saw shape. VSEPR theory predicts a pseudo-trigonal pyramidal disposition of the five electron pairs around the selenium atom. The axial Se-F bonds are 177 pm with an F-Se-F bond angle of 169.2°. The two other fluorine atoms are attached by shorter bonds (168 pm), with an F-Se-F bond angle of 100.6°. In solution at low concentrations this monomeric structure predominates, but at higher concentrations evidence suggests weak association between SeF4 molecules leading to a distorted octahedral coordination around the selenium atom. In the solid the selenium center also has a distorted octahedral environment.

Reactions

In HF, SeF4 behaves as a weak base, weaker than sulfur tetrafluoride, SF4 (Kb= 2 X 10−2):

SeF4 + HF → SeF3+ + HF2−; (Kb = 4 X 10−4)

Ionic adducts containing the SeF3+ cation are formed with SbF5, AsF5, NbF5, TaF5, and BF3.[3] With caesium fluoride, CsF, the SeF5− anion is formed, which has a square pyramidal structure similar to the isoelectronic chlorine pentafluoride, ClF5 and bromine pentafluoride, BrF5.[4] With 1,1,3,3,5,5-hexamethylpiperidinium fluoride or 1,2-dimethylpropyltrimethylammonium fluoride, the SeF62− anion is formed. This has a distorted octahedral shape which contrasts to the regular octahedral shape of the analogous SeCl62−. [5]

Explanation:

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marshall27 [118]
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The boiling point of chloroform is 61.7 C. The enthalapy of vaporization is 31.4 kj/mol. Caculate the entropy of vaporization. D
dedylja [7]

Answer:

Δ S = 93.8 J/mol-K

Explanation:

Given,

Boiling point of chloroform = 61.7 °C

                                             = 273 + 61.7 = 334.7 K.

Enthalapy of vapourization = 31.4 kJ/mol.

Using Gibbs free   energy equation

Δ G = Δ H - T (ΔS)

at equilibrium (when the liquid is boiling), Δ G = 0

so,  0 = ΔH - T (Δ S)

      T (Δ S) = Δ H

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Δ S = 93.8 J/mol-K

6 0
3 years ago
How does carbon 14 work
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6 0
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What is the nuclear binding energy for thorium-234? 2.78 × 10-10 J 3.36 × 10-14 J 1.67 × 1017 J 5.35 x 10-23 J
grin007 [14]
The correct option is A.
To calculate the binding energy, you have to find the mass defect first.
Mass defect = [mass of proton and neutron] - Mass of the nucleus
The molar mass of thorium that we are given in the question is 234, the atomic number of thorium is 90, that means the number of neutrons in thorium is 
234 - 90 = 144.
The of proton in thourium is 90, same as the atomic number.
Mass defect = {[90 * 1.00728] +[144* 1.00867]} - 234
Note that each proton has a mass of 1.00728 amu and each neutron has the mass of 1.00867 amu.
Mass defect = [90.6552 + 145.24848] - 234 = 1.90368 amu.
Note that the unit of the mass is in amu, it has to be converted to kg
To calculate the mass in kg
Mass [kg] = 1.90368 * [1kg/6.02214 * 10^-26 = 3.161135 * 10^-27
To calculate the binding energy
E = MC^2
C = Speed of light constant = 2.9979245 *10^8 m/s2
E = [3.161135 * 10^-27] * [2.9979245 *10^8]^2
E = 2.84108682069 * 10^-10.
Note that we arrive at this answer because of the number of significant figures that we used.
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And organism too

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