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3 years ago

What is the kb of a 0.0200 m ( at equilibrium) solution of methyl amine, ch3nh2, that has a ph of 11.40?

1 answer:

8 0

Answer: Kb = 3.15 × 10 ⁻⁴

Explanation:

This is how you calculate Kb for this reaction.

1) Equilibrium equation:

CH₃NH₂ + H₂O ⇄ CH₃NH₃⁺ + OH⁻

2) Kb = [CH₃NH₃⁺] [OH⁻] / [CH₃NH₂] ↔ all the spieces in equilibrium

3) From the stoichiometry [CH₃NH₃⁺] = [OH⁻]

Then, Kb = [OH⁻] [OH⁻] / [CH₃NH₂] = [OH⁻]² / [CH₃NH₂]

4) You get [OH⁻] from the pH in this way:

pOH + pOH = 14 ⇒ pOH = 14 - pH = 14 - 11.40 = 2.60

pOH = - log [OH⁻] = 2.60 ⇒ [OH⁻] = 10^(-2.6) = 0.002512

5) [CH₃NH₂] in equilibrium is given: 0.0200M

6) Now compute:

Kb = (0.002512)² / 0.0200 = 3.15 × 10 ⁻⁴

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A. Match the term with its definition. (1 point)

Assoli18 [71]

Taking into account the definition of wavelength, frecuency and propagation speed:

Frequency: The number of waves passing a point in 1 second.
Wavelength: The distance between two adjacent wave peaks.
Velocity: The direction and speed at which a wave is traveling.

The equation that illustrates the relationship between wave velocity, frequency, and wavelength is v = f×λ.

<h3>Wavelength</h3>

Wavelength is the minimum distance between two successive points on the wave that are in the same state of vibration. It is expressed in units of length (m).

<h3>Frequency</h3>

On the other side, frequency is the number of vibrations that occur in a unit of time. Its unit is s⁻¹ or hertz (Hz).

<h3>Propagation speed or velocity</h3>

Finally, the propagation speed is the speed with which the wave propagates in the medium, that is, it is the magnitude that measures the speed at which the wave disturbance propagates along its displacement.

The propagation speed relate the wavelength (λ) and the frequency (f) inversely proportional using the following equation:

v = f×λ

All electromagnetic waves propagate in a vacuum at a constant speed of 2,998 x 10⁸ m / s, the speed of light.

Therefore, the previous expression establishes an inversely proportional relationship between the frequency and the wavelength: The higher the frequency, the lower the wavelength and when the frequency is lower, the greater the wavelength.

<h3>Summary</h3>

In summary, the definition of frequency, wavelength and velocity are:

Frequency: The number of waves passing a point in 1 second.
Wavelength: The distance between two adjacent wave peaks.
Velocity: The direction and speed at which a wave is traveling.

Finally, the equation that illustrates the relationship between wave velocity, frequency, and wavelength is v = f×λ.

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3 0

2 years ago

Which law states that the volume and absolute temperature of a fixed quantity of gas are directly proportional under constant pr

Delvig [45]

<h2>Hello!</h2>

The answer is: Charle's Law.

The law that states that the volume and absolute temperature of a fixed quantity of gas (ideal gas) are proportional under constant pressure is the Charle's Law, also known as the law of volumes.

The law describes how a gas kept under constant pressure tends to expand when the temperature increases and it's described by the following equation:

$\frac{V}{T}=k$

Where,

$V=Volume\\T=Temperature\\k=constant$

Also, to describe the relationship between two differents volumes at different temperatures, we have:

$\frac{V_{i}}{T_{i}}=\frac{V_{f}}{T_{f}}$

Where,

$V_{i}=InitialVolume\\T_{i}=InitialTemperature\\V_{f}=FinalVolume\\T_{f}=FinalTemperature$

Have a nice day!

8 0

3 years ago

Read 2 more answers

H3PO4 + Ca(OH)2 → Ca(H2PO4)2 + H2O

aniked [119]

Given question is incomplete. The complete question is as follows.

Balance the following equation:

$H_3PO_4 + Ca(OH)_2 \rightarrow Ca(H_2PO_4)_2 + H_2O$

Answer: The balanced chemical equation is as follows.

$2H_3PO_4 + Ca(OH)_2 \rightarrow Ca(H_2PO_4)_2 + 2H_2O$

Explanation:

When a chemical equation contains same number of atoms on both reactant and product side then this equation is known as balanced equation.

For example, $H_3PO_4 + Ca(OH)_2 \rightarrow Ca(H_2PO_4)_2 + H_2O$

Number of atoms on reactant side:

H = 5

P = 1

O = 6

Ca = 1

Number of atoms on product side:

H = 6

P = 2

O = 9

Ca = 1

In order to balance this equation, we will multiply $H_3PO_4$ by 2 on reactant side and we will multiply $H_2O$ by 2 on product side. Hence, the balanced chemical equation is as follows.

$2H_3PO_4 + Ca(OH)_2 \rightarrow Ca(H_2PO_4)_2 + 2H_2O$

8 0

3 years ago

What is the value of delta Hrxn for this equation:

Ratling [72]

Answer:

The ΔHrxn for the above equation = 179 kJ/mol

Explanation:

The reaction bond enthalpies are for the reactant;

3 × N-H = 3 × 390 = 1,170 kJ/mol

2 × O=O = 2 × 502 = 1004 kJ/mol

The reaction bond enthalpies are for the product;

3 × N-O = 3 × 201 = 603 kJ/mol

3 × O-H = 3 × 464 = 1,392 kJ/mol

The ΔHrxn for the above equation is therefore;

ΔHrxn = 1,170 + 1,004 - (603 + 1,392) = 179 kJ/mol

6 0

3 years ago

A 0.43g samle of KHP required 24.11cm of NaOH for neutralization. Calculate the molarity of NaOH

expeople1 [14]

Answer:

0.083 M

Explanation:

We'll begin by calculating the number of mole in 0.43 g of KHP (potassium hydrogen phthalate, C₈H₅O₄K). This is can be obtained as follow:

Mass of C₈H₅O₄K = 0.43 g

Molar mass of C₈H₅O₄K = (8×12) + (5×1) + (16× 4) + 39

= 96 + 5 + 64 + 39 = 204 g/mol

Mole of C₈H₅O₄K =?

Mole = mass / molar mass

Mole of C₈H₅O₄K = 0.43 / 204

Mole of C₈H₅O₄K = 0.002 mole

Next, we shall determine the number of mole of NaOH required to react with 0.43 g (i.e 0.002 mole) of KHP. This can be obtained as follow:

C₈H₅O₄K + NaOH → C₈H₄O₄KNa + H₂O

From the balanced equation above,

1 mole of KHP reacted with 1 mole of NaOH.

Therefore, 0.002 mole of KHP will also react with 0.002 mole of NaOH.

Next, we shall convert 24.11 cm³ to L. This can be obtained as follow:

1000 cm³ = 1 L

Therefore,

24.11 cm³ = 24.11 cm³ × 1 L / 1000 cm³

24.11 cm³ = 0.02411 L

Finally, we shall determine the molarity of NaOH. This can be obtained as follow:

Mole of NaOH = 0.00 2 mole

Volume = 0.02411 L

Molarity of NaOH =?

Molarity = mole /Volume

Molarity of NaOH = 0.002 / 0.02411

Molarity of NaOH = 0.083 M

3 0

3 years ago