contestada

Ammonia, NH3, is a weak base with a Kb = 1.8 x 10-5. In a 0.8M solution of ammonia, which has a higher concentration: ammonia (NH3) or its conjugate acid the ammonium ion (NH4+)?

Respuesta :

Dejanras

Answer is: concentration ammonia is higher than concentration of ammonium ion.
Chemical reaction of ammonia in water: NH₃ + H₂O → NH₄⁺ + OH⁻.
Kb(NH₃) = 1,8·10⁻⁵.
c₀(NH₃) = 0,8 mol/L.
c(NH₄⁺) = c(OH⁻) = x.
c(NH₃) = 0,8 mol/L - x.
Kb = c(NH₄⁺) · c(OH⁻) / c(NH₃).
0,000018 = x² /  0,8 mol/L - x. 

x²  + 0,000018x - 0,0000144 = 0.

solve quadratic equation: x = c(NH₄⁺) = 3,79·10⁻³ mol/L.

The [tex]\rm K_b[/tex] is the base dissociation constant for the reaction. In 0.8 M solution of ammonia, ammonia has higher concentration.

What is the concentration of ionic species in a compound?

The dissociation reaction for ammonia is given as:

[tex]\rm NH_3\;+\;H_2O\;\rightarrow\;NH_4^+\;+OH^-[/tex]

The base dissociation constant for the reaction is given as:

[tex]\rm K_b=\dfrac{[NH_4^+]\;[OH^-]}{[NH_3]}[/tex]

The concentration of ammonium and hydroxide ion is given in the table attached below.

Substituting the values for concentration as:

[tex]\rm 1.8\;\times\;10^{-5}=\dfrac{[x]\;[x]}{0.8-x}\\ x=3.79\;\times\;10^{-3}[/tex]

The concentration of ammonia is given as:

[tex]\rm NH_3+=0.8-x\\\\NH_3=0.8-3.79\;\times\;10^{-3}\\\\NH_3=0.796\;M[/tex]

The concentration of ammonia is 0.796 M, while the concentration of ammonium ion is [tex]3.79\;\times\;10^{-3}[/tex] M.

Thus, the concentration of ammonia is higher than ammonium ion.

Learn more about base dissociation constant, here:

https://brainly.com/question/4256113

Ver imagen shrutiagrawal1798