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4 years ago

What is the electronic configuration of a selenium atom (se)?

Chemistry

2 answers:

antoniya [11.8K]4 years ago

7 0

1s22s22p63s23p63d104s24p4
or
[Ar] 3d10 4s2 4p4

saw5 [17]4 years ago

3 0

Answer:

$1s^{2}2s^{2}2p^{6} 3s^{2} 3p^{6} 4s^{2} 3d^{10} 4p^{4}$

Explanation:

For this exercise is necessary to know the atomic number of Se, which is 34 and indicate the numbers of electrons that has this atom.

For the electronic configuration you just need to follow the direction of the arrow indicated in the attached image, which shows the distribution of the electrons in the atomic orbitals, until complete the 34 electrons that has the selenium atom. The super index indicates the number of electrons in a specific atomic orbital. Then the electron configuration of selenium atom is:

$1s^{2}2s^{2}2p^{6} 3s^{2} 3p^{6} 4s^{2} 3d^{10} 4p^{4}$

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Consider the titration of a 73.9 mL sample of 0.13 M HC2H3O2 with 6.978 M NaOH. Ka(HC2H3O2) = 1.8x10-5 Determine the initial pH

Alexeev081 [22]

Answer:

1. pH = 2,82

2. 3,20mL of 1,135M NaOH

3. pH = 3,25

Explanation:

The buffer of acetic acid (HC₂H₃O₂) is:

HC₂H₃O₂ ⇄ H⁺ + C₂H₃O₂⁻

The reaction of HC₂H₃O₂ with NaOH produce:

HC₂H₃O₂ + NaOH → C₂H₃O₂⁻ + Na⁺ + H₂O

And ka is defined as:

ka = [H⁺] [C₂H₃O₂⁻] / [HC₂H₃O₂] = 1,8x10⁻⁵ (1)

1. When in the solution you have just 0,13M HC₂H₃O₂ the concentrations in equilibrium will be:

[H⁺] = x

[C₂H₃O₂⁻] = x

[HC₂H₃O₂] = 0,13 - x

Replacing in (1)

[x] [x] / [0,13-x] = 1,8x10⁻⁵

x² = 2,34x10⁻⁶ - 1,8x10⁻⁵x

x² - 2,34x10⁻⁶ + 1,8x10⁻⁵x = 0

Solving for x:

x = - 0,0015 (Wrong answer, there is no negative concentrations)

x = 0,0015

As [H⁺] = x = 0,0015 and pH is -log [H⁺], pH of the solution is 2,82

2. The equivalence point is reached when moles of HC₂H₃O₂ are equal to moles of NaOH. Moles of HC₂H₃O₂ are:

0,0466L × (0,078mol / L) = 3,63x10⁻³ moles of HC₂H₃O₂

In a 1,135M NaOH, these moles are reached with the addition of:

3,63x10⁻³ moles × (L / 1,135mol) = 3,20x10⁻³L = 3,20mL of 1,135M NaOH

3. The initial moles of HC₂H₃O₂ are:

0,0172L × (0,128mol / L) = 2,20x10⁻³ moles of HC₂H₃O₂

As the addition of NaOH spent HC₂H₃O₂ producing C₂H₃O₂⁻. Moles of C₂H₃O₂⁻ are equal to moles of NaOH and moles of HC₂H₃O₂ are initial moles - moles of NaOH. That means:

0,46x10⁻³L NaOH × (0,155mol / L) = 7,13x10⁻⁵ moles of NaOH ≡ moles of C₂H₃O₂⁻

Final moles of HC₂H₃O₂ are:

2,20x10⁻³ - 7,13x10⁻⁵ = 2,2187x10⁻³ moles of HC₂H₃O₂

Using Henderson-Hasselbalch formula:

pH = pka + log₁₀ [C₂H₃O₂⁻] / [HC₂H₃O₂]

Where pka is -log ka = 4,74. Replacing:

pH = 4,74 + log₁₀ [7,13x10⁻⁵] / [2,2187x10⁻³ ]

pH = 3,25

I hope it helps!

4 0

4 years ago

D: ____________________________________________

Vikki [24]

Answer:

I think the awnser would be c urf mom

Explanation:

4 0

3 years ago

A solution of dispersant is made by taking 15.0 mL of a 50.0 mg/mL solution of Randyne and mixing it with 50.0 mL of water. Calc

Len [333]

Answer:

The final concentration of the Randyne in grams per milliliter = 0.011 g/mL

Explanation:

As we know

C1V1 = C2V2

C1 and C2 = concentration of solution 1 and 2 respectively

V1 and V2 = Volume of solution 1 and 2 respectively

Substituting the given values, we get -

$50 * 15 = X * (15+50)\\X = 11.54$ mg/mL

The final concentration of the Randyne in grams per milliliter = 0.011 g/mL

8 0

3 years ago

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tekilochka [14]

False.

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3 years ago

Which of the following is not considered to be an acceptable use for recycled water

Klio2033 [76]

We could not use recycled water for drinking purposes. That is because it may cause us to get sick.

5 0

3 years ago