Standarize the basic and acidic solution

EXPERIMENT

To become familiar with titration to determine the molarity and pH of an acid solution

Introduction:

Arrhenius acid is a substance that ionizes in water to produce hydronium ions in an aqueous medium and Arrhenius base is a substance that ionizes in water to produce hydroxide ions in water.

According to the Bronsted-Lowery concept, an acid is a proton donor and a base is a proton acceptor.

A neutralization is a specific term used for the reaction of an acid with a base or specifically, the main feature of this reaction is that in this reaction hydronium ion reacts with the hydroxide ion to form water. we will perform a neutralization reaction to standardize the solution. Standardization is a process to determine the exact concentration of a solution.

Titration is a technique used to measure the volume of a solution that will be required to react with another agent is called titration. During titration, an indicator solution is used. The indicator is a solution that changes colour at different pH values. During titration, an endpoint is reached when an acid reacts with the base and this endpoint is determined by a change in the colour of the indicator. An endpoint is a point in a titration at which an indicator solution changes its colour. For example, Phenolphthalein changes colour from colourless to pink at pH 9. In a slightly more acidic solution, it is colourless whereas in a more alkaline solution it is pink.

The equivalent point is a theoretical point in the titration. It is a point at which stoichiometrically equal quantities are brought together.

When an acidic solution is titrated with a basic solution, concentration or molarity of unknown can be calculated by the following calculations. M1V1 = M2V2. Molarity is defined as the number of moles per liter of solution. Another concept known as the pH concept is used to measure the acidity of solution and this concept has a relation with molarity. pH is defined as the negative log of hydronium ion concentration of the solution.

Reaction:

 \[NaOH \; + \; HCL \; \rightarrow \; NaCl \; + \; H_{2}O\]

Apparatus:

• 600mL beaker
• 250 mL Erlenmeyer flask
• Ring stand
• Buret clamp
• Electronic balance
• 50mL Burette
• 500mL Erlenmeyer flask
• Wash bottle

Chemicals:

• Sodium hydroxide NaOH
• Hydrochloric acid HCl
• Phenolphthalein solution

Procedure:

Part A: Standardization of NaOH solution:

• Fill the burette with NaOH. Remove air bubbles if any in the burette and make sure that the lower meniscus is at zero points.
• Take 10mL HCl in an Erlenmeyer flask and add few drops of phenolphthalein solution to it.
• Start to add NaOH into the Erlenmeyer flask containing HCl and indicator.
• After sometimes the pink color will begin to appear at the point where the drop of NaOH falls.
• Now add NaOH drop by drop until the solution turns from colouless to pink.
• Read the burette reading and record it.
• Repeat the procedure 3-4 times until concordant readings are obtained.
• Calculate the molarity of the sodium hydroxide by using recorded readings.
  

Part B: Analysis of unknown acid:

Obtain 10mL of the unknown solution. Add a few drops of phenolphthalein and titrate it against the standard solution of NaOH solution as in part A.

Observations and calculations:

Part A:

Molarity of HCl solution = MA = ________    Volume of HCl used = VA = ________

Molarity of NaOH solution = MB = ________    Volume of NaOH used = VB = ________

* Molarity of NaOH solution is calculated from the formula    MA X VA = MB X VB

Part B:

Volume of unknown acidic solution = VA = ________

Volume of NaOH solution used = VB = ________

Molarity of NaOH from part A = MB = ________

Molarity of unknown acid = MA = ________

* Molarity of unknown acid is calculated from the formula    MA X VA = MB X VB

Results:

The molarity of NaOH is ________ and the molarity of unknown acid is _________