Methylamine is a weak base for which kb is 4.4*10 −4 . calculate the ph of a solution made by dissolving 0.070 mol of methylamine in water and diluting to 800 ml.

Answer is: pH of methylamine is 11.78.

Chemical reaction: CH₃NH₂(aq)+ H₂O(l) ⇌ CH₃NH₃⁺(aq) + OH⁻(aq).
Kb(CH₃NH₂) = 4,4·10⁻⁴.
c₀(CH₃NH₂) = n(CH₃NH₂) ÷ V(CH₃NH₂).

c₀(CH₃NH₂) = 0.070 mol ÷ 0.8 L = 0.0875 M.

c(CH₃NH₃⁺) = c(OH⁻) = x.

c(NH₂OH) = 0.0875 M - x; equilibrium concentration of methylamine.

Kb = c(CH₃NH₃⁺) · c(OH⁻) / c(CH₃NH₂).

0.00044 = x² /  (0.0875 M - x). 

Solve quadratic equation: x = c(OH⁻) = 0.00598 M.

pOH = -log(0.00598 M) = 2.22.

pH = 14 - 2.22 = 11.78.

when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.

answer:

the reaction is type of combination reaction.

explanation:

on the product side, there are 2 molecules of bonded to fe   which means one atom of fe are combined two molecules of . so, balanced chemical equation becomes :

this reaction follows the reaction type of combination reaction. a combination reaction is defined as chemical reaction in which reactants combines together to form a single product.