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ABS - Titrations (Lesson)

Titrations

Introduction

A titration is a laboratory technique where a solution of known concentration is used to determine the concentration of an unknown solution. Typically, the titrant (the known solution) is added from a buret to a known quantity of the analyte (the unknown solution) until the reaction is complete. An acid-base indicator is used to determine the end point.

Titration Calculations

Let’s take a closer look at the process for completing titration calculations to determine the concentration of an unknown solution.

Complete the Following Neutralization Equations Practice

Solving Neutralization Reaction Titration Problems

Let's take a closer look at the Mole to Mole Conversions.

The first step in a neutralization reaction titration problem is to write the chemical reaction that takes place. After the correct reaction has been written and balanced, a simple formula can be used to calculate missing pieces of data.

(moles H+/1 mole A)(MA)(VA) = (moles OH-/1 mole B)(MB)(VB)

where:

  • moles of H+ and moles of OH- are also known as the number of equivalents in the Acid-Base Titration.
  • MA and MB are the molarity of the acid and base, respectively, measured in M
  • VA and VB are the volume of the acid and base used, respectively
  • VA and VB can be in any volume unit, as long as they are the same unit

Follow the example below.

In a titration of HCl with NaOH, 100.0 mL of the base was required to neutralize 20.0 mL of 5.0 M HCl. What is the molarity of the NaOH? (Be sure to write the neutralization reaction.)

Step 1:

Write the neutralization reaction.

  • HCl + NaOH -- H2O + NaCl

Step 2:

By looking at the balanced chemical reaction, determine the moles of H+ and moles of OH-.

  • moles H+ = 1
  • moles OH- = 1

These values are determined by looking at the formula for the acid and base.

Step 3:

Identify the other pieces of information that the problem gives and determine what is being asked.

  • MA = 5.0 M
  • VA = 20.0 mL
  • MB = ?
  • VB = 100.0 mL

Step 4:

Plug in the known values and solve for the unknown value.

  • (moles H+/1 mole A)(MA)(VA) = (moles OH-/1 mole B)(MB)(VB)
  • (moles H+/1 mole A)(5.0M)(20.0mL) = (1 moles OH-/1 mole B)(100.0mL)(MB)
  • (5.0M)(20.0mL) = (100.0mL)(MB)
  • MB=1.0 M NaOH

Solving Neutralization Reaction Titration Problems Practice

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