   Chapter 16, Problem 66PS

Chapter
Section
Textbook Problem

Calculate the hydronium ion concentration and the pH when 50.0mL of 0.40M NH 3 is mixed with 50.0mL of 0.40 M HCl.

Interpretation Introduction

Interpretation:

The hydronium ion concentration and the pH has to be calculated when 50.0mL of 0.40M NH3 is mixed with 50.0mL of 0.40 M HCl.

Concept introduction:

Equilibrium constants:

The equilibrium constant is used to quantitative measurement of the strength of the acid and bases in the water.

Ka is acid constant for equilibrium reactions.

HA + H2OH3O++ A-Ka[H3O+][A-][HA]

Kb is base constant for equilibrium reaction.

BOH + H2OB++ OH-Ka[B+][OH-][BOH]

Ionic product constant for water  Kw= [H3O+][OH-]       =1.00×10-14 pH = -log[H3O+]pOH= -log[OH-]Reltion between pH and pOH pH + pOH =14

Explanation

Given volume of 0.40MNH3 = 50mL

And it is mixed with 50mL of 0.40M HCl. Therefore, the hydronium ions from HCl neutralize ammonia a weak base to its conjugate acid. NH4+.

Hydronium ions reacts with ammonia to give NH4+.

The equilibrium chemical reaction is as follows.

NH3(aq) +H3O+(aq) NH4+(aq) + H2O(aq)

Let’s calculate the amount of consumed HCl:

(50mL×1L1000mL) × (0.40molL)=  0.02 mol

Let’s calculate the consumed amount of NH3

(50mL×1L1000mL) × (0.40molL)=  0.02 mol

Let’s calculate the produced amount of NH4+ after completion of reaction.

= 0.02mol NH3  × 1mol NH4+1mol NH3= 0.02 mol NH4+

The total volume of solution = 50.0mL + 50.0mL= 100.0mL × 1L1000mL= 0.1L

Concentration ofNH4+=0.02 mol0.1L= 0.2M

Therefore, 0.2M is the final volume of NH4+ after completion of the reaction.

The NH4+ ions react with water. The resulting solution is acidic in nature.

The equilibrium reaction is as follows.

NH4+(aq) + H2O(l) NH3(aq) + H3O+(aq)

The equilibrium expression:

Ka[NH3][H3O+][NH4+]

Ka of NH4+ is 5

Still sussing out bartleby?

Check out a sample textbook solution.

See a sample solution

The Solution to Your Study Problems

Bartleby provides explanations to thousands of textbook problems written by our experts, many with advanced degrees!

Get Started

The BMI standard is an excellent tool for evaluating obesity in athletes and the elderly. T F

Nutrition: Concepts and Controversies - Standalone book (MindTap Course List)

What is the nucleolus, and what is its function?

Biology: The Dynamic Science (MindTap Course List)

Match the term listed in Column A with its definition from Column B

Nutrition Through the Life Cycle (MindTap Course List) 