Question

What is [OH⁻] in a solution of 1.25 M NH₃ and 0.78 M NH₄NO₃?

a) 1.8 × 10⁻⁵ M
b) 1.5 × 10⁻⁴ M
c) 2.5 × 10⁻⁴ M
d) 3.0 × 10⁻³ M

Answer 1

The question requires calculating the hydroxide ion concentration in a solution of NH3 and NH4NO3, which is an equilibrium problem in chemistry. However, without the equilibrium constant for NH3 (Kb), the calculation cannot be completed accurately.

Step-by-step explanation:

The student is asking about hydroxide ion concentration [OH−] in a mixed solution of ammonia (NH3) and ammonium nitrate (NH4NO3). This is a typical equilibrium problem involving weak bases and their conjugate acid salts in aqueous solutions, which is commonly taught in college-level chemistry courses.

To solve for [OH−], we need to apply the equilibrium principle for the dissociation of NH3 in water, which produces OH− and NH4+, and consider the shift in equilibrium due to the common ion effect from NH4+ already present from NH4NO3.

However, the information provided in the question is inadequate for a precise calculation without additional data such as the equilibrium constant (Kb) for NH3. Consequently, we cannot confidently conclude the correct [OH−] without this key piece of information.