Acid-base titration. Objective To determine the concentration of sulphuric acid (H2SO4) using sodium carbonate (Na2CO3) as the primary standard in volumetric analysis.

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Tsuen Wan Public Ho Chuen Yiu Memorial College

Form 6 Chemistry Practical

Experiment 1: ACIS-BASE TITRATION

Date of experiment: 24-9-2010

  1. Objective

To determine the concentration of sulphuric acid (H2SO4) using sodium carbonate (Na2CO3) as the primary standard in volumetric analysis.

  1. Introduction

A major part of chemistry is being able to analyze compounds to see how much of a given chemical they contain. One method that is often used is volumetric analysis. We use a known solution and react it with a solution of the chemical being studied. The typical way of doing this is in a titration. The essential procedure consists of running a solution from a burette into a known volume of another solution as measured out by a pipette in a conical flask, until the two solutions have just reacted completely with each other. This is the equivalence point of the reaction. This point is often marked by the change in colour of a chemical called an indicator. The solution in the burette is called the titrant while the volume of it used to reach the end point is called the titre.

Usually, the titration is carried out by neutralization:

          Acid+ Base                      Salt + H2O

OR       Acid+ Carbonate                 Salt + CO2 + H2O

  1. Chemicals used

Anhydrous sodium carbonate                    About 1.3 g

Sulphuric acid                                         A big bottle shared

Methyl orange indicator                            Several drops per time

  1. Apparatus

Weighing bottle x 1

Electronic balance x 1

100cm3 beaker        x 2

Glass rod x 1

250.0 cm3 volumetric flask        x 1

Filter funnel        x 1

Dropper x 1

50.0 cm3 burette x 1

Stand x 1

Burette clamp x 1

White tile x 1

  1. Procedure

A.        Preparation of Standard Sodium Carbonate Solution

  1. The mass of the weighing bottle was weighed using an electronic balance.
  2. Sodium carbonate was added to the weighing bottle carefully with a spatula. The mass of the weighing bottle with sodium carbonate was weighed. The masses weighed were recorded. By weighing by difference, 1.3 g of sodium carbonate could be measured accurately.
  3. The weighed sodium carbonate was poured into a clean dry 100 cm3 beaker.
  4. About 40 cm3 of distilled water was poured into the beaker. The mixture was stirred with a clean glass rod until all sodium carbonate had dissolved.
  5. The sodium carbonate solution was poured into a 250.0 cm3 volumetric flask through a filter funnel. The beaker was rinsed with a small amount of distilled water and the rinse was transferred into the volumetric flask. The step of rinsing was repeated twice. The funnel was rinsed carefully with distilled water.
  6. Distilled water was added to the volumetric flask carefully until the liquid level is about 1 cm below the graduated mark on the flask. (Use a washing bottle directly in the beginning, followed by using a dropper.)
  7. The flask was placed on bench and the solution was allowed to settle. Using a dropper, water was added drop by drop to the flask until the meniscus just touches the graduated mark.
  8. The volumetric flask was stoppered tightly. It was turned upside down and shook several times in order to mix the sodium carbonate with water thoroughly.
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B. Using Standard Sodium Carbonate to titrate Sulphuric Acid

  1. Dilution of H2SO4: 25cm3 of the given bench sulphuric acid in a beaker was pipetted into a 250.0 cm3  volumetric flask. The beaker was rinsed with a small amount of distilled water and the rinse was transferred into the volumetric flask. The step of rinsing was repeated twice. Distilled water was added to the volumetric flask carefully. The volumetric flask was stoppered tightly. It was turned upside down and shook several times in order to mix the sulphuric acid with water thoroughly.
  2. The ...

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