R the titration of 70.0 mL of 0.300 M NH 3 with 0.500 M HCl at 25 ∘ C, determine the relative pH at each of these points. Determine the relative pH before the addition of any HCl .

pH = 11.36

Explanation:

Before the addition of any HCl, you have 0.300M NH₃ in equilibrium with water:

NH₃(aq) + H₂O(l) ⇄ NH₄⁺(aq) + OH⁻(aq)

When system is in equilibrium:

Kb = 1.8x10⁻⁵ = [NH₄⁺] [OH⁻] / [NH₃]

Concentrations in equilibrium are:

[NH₃] = 0.300M - X

[NH₄⁺] = X

[OH⁻] = X

1.8x10⁻⁵ = [X] [X] / [0.300M - X]

5.4x10⁻⁶ - 1.8x10⁻⁵X = X²

X² + 1.8x10⁻⁵X - 5.4x10⁻⁶ = 0

Solving for X:

X = -0.00233 → False answer, there is no negative concentrations

X = 0.00231 → Right answer.

As [OH⁻] = X; [OH⁻] = 0.00231

As pOH = -log [OH⁻] = 2.636

14 = pOH + pH

14 - pOH = pH

pH = 11.36

b..

is the correct one

explanation:

covalent bonds form as valence electrons are shared between two atoms. lewis structures and structural formulas are common ways of showing the covalent bonding in organic molecules. formal charge describes the changes in the number of valence electrons as an atom becomes bonded into a molecule.