Chemistry, 30.07.2019 06:30 HurpsGaming1

Determine the ph of 0.57 m methylamine (ch3nh2) with kb = 4.4 x 10-4 : ch3nh2(aq)+ h2o(l) ⇌ ch3nh3+ (aq) + oh- (aq)

Answers: 1

Show answers

Answers

Answer is: pH of methylamine is 12,2.
Chemical reaction: CH₃NH₂(aq)+ H₂O(l) ⇌ CH₃NH₃⁺(aq) + OH⁻(aq).
Kb(CH₃NH₂) = 4,4·10⁻⁴.

c₀(CH₃NH₂) = 0,57 M.

c(CH₃NH₃⁺) = c(OH⁻) = x.

c(NH₂OH) = 0,57 M - x.

Kb = c(CH₃NH₃⁺) · c(OH⁻) / c(CH₃NH₂).

0,00044 = x² / (0,57 M - x).

Solve quadratic equation: x = c(OH⁻) = 0,0156 mol/L.

pOH = -log(0,0156 mol/L.) = 1,80.

pH = 14 - 1,80 = 12,2.

Answer from: paovue48

The pH value is 12.2

Further explanation

Given:

0.57 M methylamine (CH₃NH₂) $K_b = 4.4 \times 10^{-4}$

Question:

The pH value of methylamine

The Process:

Methylamine is a weak base. When a weak base reacts with water, it produces its conjugate acid and hydroxide ions.

$\boxed{ \ CH_3NH_2_{(aq)} + H_2O_{(l)} \rightleftharpoons CH_3NH_3_{(aq)} + OH^-_{(aq)} \ }$

CH₃NH₂ is the conjugate acid of CH₃NH₂.The concentration of hydroxide ions is needed to calculate pH.

Let's prepare the equilibrium system to calculate the concentration of hydroxide ions. In chemical equilibrium, the liquid phase has no effect.

Initial concentration (in molars): $\boxed{ \ [CH_3 NH_2] = 0.57 \ }$ Change (in molars): $\boxed{ \ [CH_3NH_2] = -x \ } \boxed{ \ [CH_3NH_3] = +x \ } \boxed{ \ [OH^-] = +x \ }$ Equilibrium (in molars): $\boxed{ \ [CH_3NH_2] = 0.57 - x \ } \boxed{ \ [CH_3NH_3] = x \ } \boxed{ \ [OH^-] = x \ }$

$\boxed{ \ K_b = \frac{ [CH_3NH_3] [OH^-] }{ [CH_3NH_2] } \ }$

Here Kb acts as Kc or equilibrium constant.

$\boxed{ \ 4.4 \times 10^{-4} = \frac{ x \cdot x }{ 0.57 - x } \ }$

$\boxed{ \ 4.4 \times 10^{-4} = \frac{x^2}{0.57 - x} \ }$

$\boxed{ \ 2.508 \times 10^{-4} - 4.4 \times 10^{-4}x = x^2 \ }$

$\boxed{ \ x^2 + 4.4 \times 10^{-4}x - 2.508 \times 10^{-4} = 0 \ }$

The solution is obtained through the formula of quadratic equations, i.e., $\boxed{ \ x = [OH^-] = 0.0156 \ M \ }$

Next, we calculated the pOH value followed by the pH value.

$\boxed{ \ pOH = -log [OH^-] \ }$

$\boxed{ \ pOH = -log [0.0156] \ }$

We get $\boxed{ \ pOH = 1.81 \ }$

$\boxed{ \ pH + pOH = 14 \ }$

$\boxed{ \ pH = 14 - pOH \ }$

$\boxed{ \ pH = 14 - 1.81 \ }$

Thus $\boxed{\boxed{ \ pH = 12.19 \ rounded \ to \ 12.2 \ }}$

- - - - - - -

Quick Steps

0.57 M methylamine (CH₃NH₂)

$K_b = 4.4 \times 10^{-4}$

We immediately use the formula to calculate the concentration of hydroxide ions for weak bases.

$\boxed{\boxed{ \ [OH^-] = \sqrt{K_b \times base \ concentration} \ }}$

$\boxed{ \ [OH^-] = \sqrt{4.4 \times 10^{-4} \times 0.57} \ }$

$\boxed{ \ [OH^-] = 0.0158 \ M \ }$

Like the steps above, we calculated the pOH value followed by the pH value.

$\boxed{ \ pOH = -log [OH^-] \ }$

$\boxed{ \ pOH = -log [0.0158] \ }$

$\boxed{ \ pOH = 1.8 \ }$

$\boxed{ \ pH = 14 - pOH \ }$

$\boxed{ \ pH = 14 - 1.8 \ }$

Thus $\boxed{\boxed{ \ pH = 12.2 \ }}$

Learn moreThe theoretical density of platinum which has the FCC crystal structure link How was the water filtered to remove debris and living organisms? link The energy density of the stored energy link

Keywords: determine, the pH, 0.57 M, methylamine, CH₃NH₂, CH₃NH₃, OH⁻, Kb, Kc, equilibrium constant, weak base

Determine the ph of 0.57 m methylamine (ch3nh2) with kb = 4.4 x 10-4 : ch3nh2(aq)+ h2o(l) ⇌ ch3nh3+

Answer from: Quest

The answer is c fish

Answer from: Quest

a compound is a molecule made of atoms from different elements.

a. by the combination of an unlimited number of elements

Another question on Chemistry

Chemistry, 22.06.2019 07:20

Why does his teacher ask him to balance the equation by including the correct coefficient

Answers: 1

Answer

Chemistry, 22.06.2019 08:30

What method(s) do plants use to obtain nitrogen? select all that apply. absorb it from the atmosphere use bacteria to convert nitrogen to usable form obtain usable nitrogen compounds from the soil absorb nitrogen from water taken in at the roots

Answers: 3

Answer

Chemistry, 22.06.2019 15:00

20 pts ‼️ an unmanned spacecraft travels to mars. mars has a lower strength of gravity than earth. where in the image is the spacecraft’s weight the greatest?

Answers: 1

Answer

Chemistry, 22.06.2019 20:00

Many free radicals combine to form molecules that do not contain any unpaired electrons. the driving force for the radical–radical combination reaction is the formation of a new electron‑pair bond. consider the chemical equation. n(g)+no(g)⟶nno(g) n(g)+no(g)⟶nno(g) write lewis formulas for the reactant and product species in the chemical equation. include nonbonding electrons. n(g)n(g) select draw rings more erase select draw rings more erase select draw rings more erase n no(g)

Answers: 1

Answer

You know the right answer?

Determine the ph of 0.57 m methylamine (ch3nh2) with kb = 4.4 x 10-4 : ch3nh2(aq)+ h2o(l) ⇌ ch3nh3+...

Questions