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Katen [24]
3 years ago
11

Why does the octet rule not always refer to a stable arrangement of eight valence electrons

Chemistry
1 answer:
bearhunter [10]3 years ago
4 0

Answer:

Explanation:

The octet rule does not always refer to a stable arrangement of eight valence electrons because there are some element that do not have eight valence electrons yet they are stable. for example;

i) Helium, It has two valence electrons and it is a stable gas.

ii) Boron triflouride (BF3); it has  six valence electrons (deficit valence electron) yet it is also stable.

iii) Phosphorus pentachloride (PCl5); it has more than eight valence electron and it is also stable.

For these few reasons it is not always advisable to say octet arrangement refer to stable eight valence electrons.  

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which of the following cannot be considered a single phase? a) a pure solid b) a pure liquid c) a homogeneous mixture d) a heter
Trava [24]
The question is asking to choose among the following choices is cannot be considered as a single phase and base on my further research and understanding about the sad topic, I would say that the answer would be <span>d) a heterogeneous mixture. I hope you are satisfied with my answer </span>
8 0
3 years ago
For the reaction: CH3NH2(aq) + H2O(aq) ⇌ CH3NH3 +(aq) + OH- Determine the change in the pH (ΔpH) for the addition of 6.7 M CH3NH
Korolek [52]

Answer:

The change in the pH (ΔpH) is 2,17

Explanation:

The reaction:

CH₃NH₂(aq) + H₂O(aq) ⇌ CH₃NH₃⁺(aq) + OH⁻

kb = \frac{[OH^{-}][CH_{3}NH_{3}^+]}{[CH_{3}NH_{2}]} <em>(1)</em>

In equilibrium, a solution of CH₃NH₂ 4,7M produces:

[CH₃NH₂] = 4,7 - x

[CH₃NH₃⁺] = x

[OH⁻] = x

Replacing in (1):

4,38x10^{-4} = \frac{x^2}{4,7-x}

x² + 4,38x10⁻⁴x - 2,0586x10⁻³ = 0

The solutions are:

x = -0,0456 No physical sense. There are not negative concentrations.

x = 0,04515 Real answer.

The concentration of [OH⁻] is 0,04515 M.

As pOH = -log [OH⁻] And pH+pOH = 14. The pH of this solution is:

<em>pH = 12,65</em>

The addition of 6,7M produce this changes in concentrations:

[CH₃NH₂] = 4,656 + x

[CH₃NH₃⁺] = 6,74515 - x

[OH⁻] = 0,04515 - x

Replacing in (1) you will obtain:

x² - 6,7907x + 0,3025 = 0

Solving for x:

x = 6,74586 No physical sense

x = 0,04484 Real answer.

Thus, [OH⁻] = 0,04515 - 0,044842 = 3,08x10⁻⁴M

pOH = 3,51.

<em>pH = 10,49</em>

Thus ΔpH is 12,65 - 10,49 = <em>2,16 ≈ 2,17</em>

I hope it helps!

4 0
3 years ago
A plant extract can be obtained with organic solvents such as acetone or ethyl alcohol, and is composed of plant pigments such a
prohojiy [21]

Answer:

Here's what I get  

Explanation:

A plant extract is a mixture because it contains different substances: acetone or ethanol, chlorophylls A and B, carotene and xanthophylls.

It is homogeneous because it is a solution. There is only one phase: the liquid phase. You cannot see the pigments as separate phases.

You can separate the pigments by paper, thin layer, or column chromatography.

Many schools use paper chromatography, because paper is cheap.

As the mixture of pigments follows the solvent up the paper, they separate into different coloured bands according to their attractive forces to the cellulose in the paper.

The chlorophylls are strongly attracted to the paper, so they don't travel very far.

The nonpolar carotene molecules have little attraction to the polar cellulose, so they are carried along by the solvent front.

8 0
3 years ago
Which of the following values are not equal to 1 mole?
Gekata [30.6K]

Answer:

none of them are equal to one mole

3 0
2 years ago
Use the periodic table to select the element that best fits each of the following descriptions. which element below has properti
xenn [34]

Answer: Boron is the element which has properties of both metals and nonmetals.

Explanation:

Metals are defined as the elements which loose electrons to attain stable electronic configuration. They attain positive charge and form cation. Example: Zinc (Zn), Aluminium (Al) , copper (Cu)

Non-metals are defined as the elements which gain electrons to attain stable electronic configuration. They attain negative charge and form anion. Example: Chlorine (Cl) , Sulphur (S)

Metalloids are defined as the elements which show properties of both metals and non-metals. There are 7 metalloids in the periodic table. They are Boron (B) , Silicon (Si) , Germanium (Ge) , Arsenic (As) ,  Antimony (Sb), Tellurium (Te) and Polonium (Po).

Thus boron is the element which has properties of both metals and nonmetals.

7 0
3 years ago
Read 2 more answers
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