Acids and Bases Neutralization and Titration

pOH, Neutralizations and Titrations

By Abby Fancsali

pOH

• ​pH measure the amount of Hydronium ions, pOH measures the amount of Hydroxide ions in a solution

  • Not used as much outside of labs to make calculations easier

  • Equation for pOH is virtually the same​ as pOH

    • ​pOH= -log [OH]

  • pH + pOH = 14

    • once you know the pH, you can find the pOH

Neutralizations

• Neutralization Reaction: a reaction between the hydronium [H₃O⁺] ions in an acid and the hydroxide [OH^-] ions in a base that forms water and a salt

  • An acid + A Base = A salt + Water

  • All Neutralizations are the same reaction between ions regardless of the type or strength of the acid or the base

    • H₃O⁺ + OH^- → 2 H₂O

    ​

Titrations

• Titration: The General addition of one solution to another to reach an equivalence point

  • Uses an acid or a bas of a known concentration to determine the concentration of an unknown

  • As a strong base is added to a strong acid, the two react until they are in amounts that use each other up, neutralizing the substance

    • Equivalence Point: the point at which a neutralization reaction is complete and the pH is equal to 7

Parts of a Titration

• Buret: a graduated glass tube with a tap at the end

• Titrand: a solution with an unknown concentration

• Titrant: a solution with a known concentration used in a titration of an unknown concentration

  • Can be either an acid or a base​

• Standard solution: a solution of known concentration

• Indicator Solution: a chemical that changes color in the presence of an acid or base

Reading a Buret

• When a liquid is added to any measuring tube, the water tends to form a dip within the container

  • Meniscus: the curved upper surface of a liquid in a tube

    • When reading from a graduated container, it is important to look at the measurement at the curve, not the edge

Reading a Buret

Fill in the Blank

What is the measurement?

Fill in the Blank

What is the measurement?

Fill in the Blank

What is the measurement?

Multiple Choice

This is the solution you know the concentration of in a titration

• Titrand

• Titrant

• Indicator Solution

• Buret

Multiple Choice

This is the solution you don't know the concentration of in a titration

• Titrand

• Titrant

• Indicator Solution

• Buret

Setting up a Titration

• Setting up Burets: Set up two clean burets

  • One is for your acid, one is for your Base

    • Rinse your acid buret with the acid and the base buret with the base three time each

  • Fill the acid buret to a point above the 0mL mark with the acid of unknown concentration

    • release some acid from the buret into the waste beaker to release air bubbles

    • Record the volume of the acid in the buret as the initial volume

  • Allow approximately the volume of acid deemed needed by the lab procedure to flow into a clean flask

    • record the amount of acid in the flask as close to the nearest 0.01 mL​

  • Add three drops of the indicator solution to the flask

Setting up a Titration

• Fill the Base Buret to the calibration point, and release a small amount into a waste beaker

  • Record the initial volume of your base to the closest 0.01 mL

• Place your Flask with the acid under the buret so that the tip of the buret rests inside the flask

• SLOWLY release base into the flask while gently swirling the Flask

  • The equivalence point is reached when a very light color remains after 30 seconds of swirling

• Subtract the initial volume reading on the buret from the final volume to find the exact amount of base added​

Multiple Choice

Which of the following results shows the equivalence point in a titration

• The solution is colorless

• The Solution is a dark color

• The Solution has a light/faint Color

Multiple Choice

The first time you do a titration on a solution, at what speed should you release your titrant?

• Dripping

• Fast

• It doesn't matter

Titration Calculations

• Once you have the volume of your solution, you can solve for the concentration of the unknown

  • Concentration would be measured Using Molarity

• Steps

  • ​Identify Balanced Chemical Equation of the reaction taking place

  • Determine the moles of your known concentration substance used

  • Convert your Moles of your known substance to Moles of your unknown substance

  • Use Your moles of unknown and amount used to determine the Molarity of the unknown

Titration Calculation Sample Problem

In a titration, 27.4 mL of 0.0154 M Ba(OH)₂ is added to a 20.0 mL sample of a HCl solution​ whose concentration is unknown until the equivalence point is reached. What is the molarity of the acid solution?

• Step 1: Identify the Balanced Equation​

Titration Calculation Sample Problem

In a titration, 27.4 mL of 0.0154 M Ba(OH)₂ is added to a 20.0 mL sample of a HCl solution​ whose concentration is unknown until the equivalence point is reached. What is the molarity of the acid solution?

• Step 1: Identify the Balanced Equation​

  • Ba(OH)₂ + 2HCl →​ BaCl₂ + 2H₂O

• Step 2: Convert the volume of your known solution into moles

  ​

Fill in the Blank

How many moles of Barium Hydroxide were used. **Put answer in Scientific notation***

Titration Calculation Sample Problem

In a titration, 27.4 mL of 0.0154 M Ba(OH)₂ is added to a 20.0 mL sample of a HCl solution​ whose concentration is unknown until the equivalence point is reached. What is the molarity of the acid solution?

• Step 1: Identify the Balanced Equation​

  • Ba(OH)₂ + 2HCl →​ BaCl₂ + 2H₂O

• Step 2: Convert the volume of your known solution into moles=4.22E-4 mol Ba(OH)₂

• Step Three: Use the mole ration to convert from Ba(OH)​

  ​

Fill in the Blank

How many moles of Hydrochloric Acid were used in our reaction. **Put answer in Scientific notation***

Titration Calculation Sample Problem

In a titration, 27.4 mL of 0.0154 M Ba(OH)₂ is added to a 20.0 mL sample of a HCl solution​ whose concentration is unknown until the equivalence point is reached. What is the molarity of the acid solution?

• Step 1: Identify the Balanced Equation​

  • Ba(OH)₂ + 2HCl →​ BaCl₂ + 2H₂O

• Step 2: Convert the volume of your known solution into moles=4.22E-4 mol Ba(OH)₂

• Step 3: Use the mole ration to convert from Ba(OH)​ to HCl= 8.44E-4 mol HCl

• Step 4: Solve for your molarity​

  ​

Fill in the Blank

In a titration, 27.4 mL of 0.0154 M Ba(OH)₂ is added to a 20.0 mL sample of a HCl solution​ whose concentration is unknown until the equivalence point is reached. What is the molarity of the acid solution? **Put answer in Scientific notation***