Which statement about the Nobel gases is most reliable

Determine the ph of a 0. 35 m aqueous solution of CH3NH2 (methylamine). The kb of methylamine is?

guajiro [1.7K]

The pH of 0.35 M of CH₃NH₂ is 12.09 and the $k_b$ for methylamine is 4.4 x 10⁻⁴.

pHis the quantitative measure of acidity and basicity of an aqueous or other liquid solution. The scale range goes from 0 to 14. Water has a pH of 7 and is neutral in nature.

<h3>What is dissociation constant?</h3>

The dissociation constant is an equilibrium constant that describes the dissociation or ionization of a base or an acid

$k_a$ describes the dissociation of an acid

$k_b$ describes the dissociation of a base

For methylamine,

$CH_3NH_2 + H_2O\Leftrightarrow CH_3NH_3^+ + OH^-$

Initial concentration of methylamine = 0.35 M

Initial concentration of products = 0

Let, at equilibrium concentration of CH₃NH₂ = 0.35 - x

Then, concentration of CH₃NH₃⁺ and OH⁻ is x and x respectively

$k_b = \frac{[CH_3NH_3^+] [OH^-]}{[CH_3NH_2]}$

The dissociation constant for methylamine, $k_b$ = 4.4 x 10⁻⁴

$4.4 \times 10^-^4 = \frac{x.x}{0.35} \\x^{2} = 4.4 \times 10^-^4 \times 0.35\\x^{2} = 1.54 \times 10^-^4 \\$

$x =0.0124$

pOH = -log[OH] = -log(0.0124) = 1.91

pH + pOH = 14

pH = 14 - 1.91 = 12.09

Thus, the pH of methylamine is 12.09 and $k_b$ is 4.4 x 10⁻⁴

Learn more about pH:

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7 0

2 years ago

Question 4

natka813 [3]

4

I can confirm that's the correct answer

5 0

2 years ago

All of the following undergo hybridization except <br><br> A. C<br> B. Si<br> C. Mg<br> D. B

Pavel [41]

Answer:

C: Mg

Explanation:

Hybridization of atomic orbitals is a fundamental concept introduced by Pauling that describes the mixing of orbitals at an atom which adds a definite direction to the Lewis - shared electron pair or electron chemical - bond concept.

Carbon(C) can hybridized on sp, sp2 and sp3 simply because it's valence shell gives room for it.

For silicon(si), when forming covalent bonds with other atoms, it's 3s and 3p orbitals are mixed with each other to form new hybrid orbitals.

Magnesium in itself doesn't hybridized except in magnesium hydrides.

Boron orbitals(B): when boron forms bonds with three other atoms like borazine, they are hybridized to either the sp2 or hybridized to the sp3 which occurs when boron forms bonds with four atoms just as is in metal borohydrides.

7 0

3 years ago

The concentration of the KCN solution given in Part A corresponds to a mass percent of 0.473 %. What mass of a 0.473 % KCN solut

tiny-mole [99]

If the Ka of HCN = 5.0 x 10^-10
Since
(Ka) (Ka) - 1 x 10^ -14
then
the Kb of its conjugate base (CN-) = 2.0 X 10^-5

since
pH + pOH = 14
when the pH = 10.00
then
the pOH = 4.00
& the OH-
would then equal 1.0 X 10^-4

NaCN as a base does a hydrolysis in water:
CN- & water --> HCN & OH-
notice that equal amounts of OH- & HCN are formed

Kb = [HCN] [OH-] / [CN-]

2.0 X 10^-5 = [1.0 X 10^-4] [1.0 X 10^-4] / [CN-]

[CN-] =(1.0 X 10^-8) / (2.0 X 10^-5)

[CN-] = (5.0 X 10^-4)

that's 0.00050 Molar
which is 0.00050 moles in each liter of aqueous KCN solution
which is
0.00025 moles KCN in 500. mL of aqueous KCN solution

use molar mass of KCN, to find grams:
(0.00025 moles KCN) (65.12 grams KCN / mole) = 0.01628 grams of KCn

which is 16.3 mg of KCN
& rounded to the 2 sig figs which are showing in the Ka of HCN , "5.0" X 10^-10
your answer would be
16 mg of KCN

sorry even after making a correction in calcs , I don't get one of your answers.
the only way that I could get one of them is to pretend that yours was a 1 sig fig problem,
in which case your 16 mg would round off to 20 mg.
but you have 3 sig figs in "500. ml", & 2 sig figs in both the "pH of 10.00."
& The Ka of HCN = "5.0 x 10^-10."

it does however take 12 mg of NaCN, to make 500. mL of aqueous solution pH of 10.00. the molar mass of NaCN has the smaller molar mass of 49.00 grams per mole.
maybe they meant NaCN, but wrote KCN instead.

I hope i answered this correctly for you.

8 0

4 years ago

What is a mammal and why are they called mammals

taurus [48]

Answer:

mammals are the animal who lay eggs

7 0

3 years ago

Read 2 more answers