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denpristay [2]
2 years ago
5

In the laboratory, a general chemistry student measured the pH of a 0.486 M aqueous solution of triethanolamine, C6H15O3N to be

10.740. Use the information she obtained to determine the Kb for this base.
Chemistry
1 answer:
STatiana [176]2 years ago
5 0

Answer:

Kb = 6.22x10⁻⁷

Explanation:

Triethanolamine, C₆H₁₅O₃N, is in equilibrium with water:

C₆H₁₅O₃N(aq) + H₂O(l) ⇄ C₆H₁₅O₃NH⁺(aq) + OH⁻(aq)

Kb is defined from concentrations in equilibrium, thus:

Kb = [C₆H₁₅O₃NH⁺] [OH⁻] / [C₆H₁₅O₃N]

The equilibrium concentration of these compounds could be written as:

[C₆H₁₅O₃N] = 0.486M - X

[C₆H₁₅O₃NH⁺] = X

[OH⁻] = X

pH is -log [H⁺], thus, [H⁺] = 10^-pH = 1.820x10⁻¹¹M

Also, Kw = [OH⁻] ₓ [H⁺];

1x10⁻¹⁴ = [OH⁻] ₓ [H⁺]

1x10⁻¹⁴ = [OH⁻] ₓ [1.820x10⁻¹¹M]

5.495x10⁻⁴M = [OH⁻], that means <em>X = 5.495x10⁻⁴M</em>

Replacing in Kb formula:

Kb = [5.495x10⁻⁴M] [5.495x10⁻⁴M] / [0.486M-5.495x10⁻⁴M]

<em>Kb = 6.22x10⁻⁷</em>

<em></em>

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Consider the following intermediate chemical equations.
vfiekz [6]

Answer:

-250.3kJ

Explanation:

Based in the reactions and using -<em>Hess's law-</em>:

(1) P₄(s) + 6 Cl₂(g) → 4PCl₃(g) ΔH₁ = -4439kJ

(2) 4PCl₅(g) → P₄(s) + 10Cl₂  ΔH₂ = 3438kJ

The sum of (1) + (2) is:

4PCl₅(g) → 4PCl₃(g) + 4 Cl₂ ΔH = -4439kJ + 3438kJ = -1001kJ

Dividing this reaction in 4:

PCl₅(g) → PCl₃(g) + Cl₂ ΔH = -1001kJ / 4 = <em>-250.3kJ</em>

8 0
3 years ago
The energy diagram illustrated in the model corresponds to what student B
KatRina [158]

Answer: Exothermic reaction

Explanation:

Exothermic reactions lose energy, or ΔH, when they react.

4 0
3 years ago
Write the condensed ground-state electron configurations of these transition metal ions, and state which are paramagnetic:
Zinaida [17]

The electron configuration of  V³⁺ is [Ar]3d^2. The ion is paramagnetic because it has two unpaired electrons

<h3>What is paramagnetic?</h3>
  • A weak magnetic field supplied externally can weakly attract some materials, which then create internal magnetic fields that are directed in the same direction as the applied magnetic field. This phenomenon is known as paramagnetic.
  • Diamagnetic materials, in contrast, are attracted to magnetic fields and produce induced magnetic fields that are directed in the opposite direction from the applied magnetic field.
  • The majority of chemical elements and some compounds are considered to be paramagnetic materials.
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7 0
2 years ago
Question 1
REY [17]

Answer:

An atom of neon-20 has one fewer proton and two fewer neutrons than an atom of sodium-23.

Explanation:

Neon - 20 and Sodium - 23

Neon - 20

Protons = 10

Neutrons = 10

Sodium - 23

Protons = 11

Neutrons = 12

With the information above and checking the options;

An atom of neon-20 has one fewer proton and two fewer neutrons than an atom of sodium-23.

This option is correct.

5 0
3 years ago
1.What is the specific heat capacity of granite when 20 kg absorbs 237 000 J of heat energy, causing its temperature to increase
Natalka [10]

<u>Given</u> :

  • Amount = 20 kg
  • Heat energy absorbed = 237,000 J
  • Temperature change = 15 °C

<u>Formula applied</u> :

\boxed {Q = mc \triangle T}

  • Q = absorbed heat
  • m = mass
  • c = specific heat capacity
  • ΔT = temperature change

Let's solve for c !

⇒ 237,000 = 20 × c × 15

⇒ c = 237,000 ÷ 300

⇒ \boxed {c = 790 J kg^{-1} K^{-1}}

∴ The specific heat capacity of granite is <u>790 J kg⁻¹ K⁻¹</u>.

5 0
1 year ago
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