Understanding Experimental Planning for Advanced Level Chemistry

The Learner's Approach

Kim Seng Chan, Jeanne Tan

• Publisher: WSPC
• Year: 2015
• eBook ISBN: 9789814667920
• Topic: Didattica
• Subtopic: Didattica della scienza e della tecnologia

This book is a continuation of authors' previous six books — Understanding Advanced Physical Inorganic Chemistry, Understanding Advanced Organic and Analytical Chemistry, Understanding Advanced Chemistry Through Problem Solving Vol. I & II, Understanding Basic Chemistry and Understanding Basic Chemistry Through Problem Solving, retaining the main refutational characteristics of the previous books with the strategic inclusion of think-aloud questions to promote conceptual understanding during an experimental planning. These essential questions would make learners aware of the rationale behind each procedural step, the amount of chemical used and types of apparatus that are appropriate for the experiment.

The book provides a fundamental important scaffolding to aid students to create their own understanding of how to plan an experiment based on the given reagent and apparatus. It guides the students in integrating the various concepts that they have learnt into a coherent and meaningful conceptual network during experimental planning.

Existing A-level or IB guidebooks generally introduce concepts in a matter-of-fact manner. This book adds a unique pedagogical edge which few can rival. This book is essential and useful in order for students to be adequately prepared for their high stake examinations.

Request Inspection Copy

This book is a continuation of authors' previous six books — Understanding Advanced Physical Inorganic Chemistry, Understanding Advanced Organic and Analytical Chemistry, Understanding Advanced Chemistry Through Problem Solving Vol. I & II, Understanding Basic Chemistry and Understanding Basic Chemistry Through Problem Solving, retaining the main refutational characteristics of the previous books with the strategic inclusion of think-aloud questions to promote conceptual understanding during an experimental planning. These essential questions would make learners aware of the rationale behind each procedural step, the amount of chemical used and types of apparatus that are appropriate for the experiment.

The book provides a fundamental important scaffolding to aid students to create their own understanding of how to plan an experiment based on the given reagent and apparatus. It guides the students in integrating the various concepts that they have learnt into a coherent and meaningful conceptual network during experimental planning.

Existing A-level or IB guidebooks generally introduce concepts in a matter-of-fact manner. This book adds a unique pedagogical edge which few can rival. This book is essential and useful in order for students to be adequately prepared for their high stake examinations.

Request Inspection Copy

Readership: A level students and teaching professionals.

CHAPTER 1

PLANNING USING TITRATION

Titration refers to a general class of experiments in which the known property (e.g., concentration) of a solution is used to infer the unknown property of another solution. A typical titration experiment requires the following apparatus:

—Pipette and pipette filler to measure the volume of the analyte or titrand;

—Burette to contain the standard solution or titrant;

—Conical flask to contain the analyte or titrand;

—Volumetric flask to make a standard solution or for carrying out a dilution; and

—An indicator (optional) such as phenolphthalein, methyl orange, starch, etc. to signal the end of a titration.

A titration set-up is shown as follows:

Q	What is a standard solution?

A:A standard solution refers to one in which its concentration is already known accurately. Since the concentration of the solution is already known, when we used a certain volume of this standard solution, we would know the number of moles of particles that is used. Hence, we can make use of this information about the number of moles to determine the number of moles of reactants in the analyte, through a balanced chemical equation.

Q	Why is a burette used to hold the standard solution?

A:A burette can measure up to two decimal places of accuracy while a pipette can only measure up to one decimal place of accuracy. Since a burette is more accurate than a pipette, it is usually used to contain the standard solution. But take note that there are exceptions in which a burette can be used to contain the non-standard solution that is used during titration. For such instances, there are usually other specific reasons for doing it.

1.1Mixture of Potassium Hydrogen Carbonate and Potassium Chloride

The Task:

A sample of potassium hydrogen carbonate, KHCO₃, contains 4–8% of potassium chloride, KCl. You are supposed to plan an experiment using titration to determine the actual percentage of the potassium hydrogen carbonate in the sample with the following chemicals and apparatus:

•0.100 mol dm⁻³ H₂SO₄ solution;

•12 g sample of potassium hydrogen carbonate and potassium chloride mixture;

•250 cm³ volumetric flask/graduated flask; and

•Standard glassware for titration.

Q	Where should we start thinking?

A:	(i)	What is the purpose of the plan?
		—	To determine the percentage by mass of the potassium hydrogen carbonate in the mixture.
	(ii)	What do you need to know in order to determine the mass of potassium hydrogen carbonate?
		—	We need to know the number of moles of potassium hydrogen carbonate that is present in a fixed mass of the sample that we have measured.
	(iii)	How do you then determine the number of moles of potassium hydrogen carbonate?
		—	We can make use of the following balanced equation for the reaction between KHCO3 and H2SO4: 2KHCO3(aq) + H2SO4(aq) → K2SO4(aq) + 2CO2(g) + 2H2O(l). Thus, if we know the number ...

Table of contents

• Cover Page
• Title Page
• Copyright page
• Preface
• Acknowledgements
• Contents
• Chapter 1 Planning Using Titration
• Chapter 2 Planning Using Gravimetric Analysis
• Chapter 3 Planning Using the Gas Collection Method
• Chapter 4 Planning for Energetics Experiments
• Chapter 5 Planning for Kinetics Experiments
• Chapter 6 Planning for Electrochemical Experiments
• Chapter 7 Planning for Inorganic Qualitative Analysis
• Chapter 8 Planning for Organic Qualitative Analysis
• Chapter 9 Planning for Organic Synthesis
• Chapter 10 Planning for Spectrophotometric Analysis
• Index