A-Level Chemistry's Best Kept Secrets!

What Top Students Know That You Don't

K W David Tan, Leonard Pereira

• Publisher: WS EDUCATION
• Year: 2018
• eBook ISBN: 9789813220140
• Topic: Physical Sciences
• Subtopic: Chemistry
• Index: Chemistry

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A-Level Chemistry's Best Kept Secrets! aims to inter-link and integrate different concepts and topics and it is written with the latest syllabus in mind. With effect from 2017, there would be a change in the A-level syllabus and the ability to cross link topics is integral to acing chemistry. Many guidebooks are of the expository and non-refutable type in which facts are presented rather than explained. In this book, novel and more efficient ways of looking at problems in chemistry are proposed to ensure good understanding of the subject.

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--> Contents:

• General and Physical Chemistry:
  • Atoms, Molecules and Stoichiometry
  • Atomic Structure
  • Chemical Bonding
  • The Gaseous State
  • Chemical Energetics
  • Electrochemistry
  • Equilibria Part 1: Chemical Equilibria
  • Equilibria Part 2: Ionic Equilibria
  • Reaction Kinetics
• Inorganic Chemistry:
  • Chemical Periodicity
  • Group II
  • Group VII
  • Introduction to Transition Elements
• Organic Chemistry:
  • Introduction — Structure and Bonding
  • Introduction — Isomerism
  • Hydrocarbons Part 1: Alkanes
  • Hydrocarbons Part 2: Alkenes
  • Hydrocarbons Part 3: Arenes
  • Halogen Derivatives
  • Hydroxy Compounds
  • Carbonyl Compounds
  • Carboxylic Acids and Their Derivatives
  • Nitrogen Compounds: Amines, Amides and Amino Acids

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--> Readership: Students taking Singapore-Cambridge GCE A-level examinations, chemistry teachers, chemistry enthusiasts, chemistry major undergraduates. -->
Keywords:A Level Chemistry;H1;H2;H3;CIE;GCE;IBReview: Key Features:

• With effect from 2017, there would be a change in the A-level syllabus and the ability to cross link topics is integral to acing chemistry. Throughout the book, much guidance is given "on the spot" and an attempt has been made to interlink different topics and concepts as required by the new syllabus
• Novel and more efficient ways of looking at problems are proposed. Such methods and techniques have been refined through my years of teaching experience with international students
• Extra emphasis based on fundamental understanding has been placed on the Organic Chemistry section to enable the students to recall the reagents and conditions easily

SECTION 1

GENERAL AND PHYSICAL CHEMISTRY

SECTION 1.1

ATOMS, MOLECULES AND STOICHIOMETRY

Mole Equations

Mole stoichiometry is at the cornerstone of quantitative Chemistry and frequently appears in many topics.

4 keys formulas:

1.no. of moles

2.no. of moles = concentration in

volume of solution in dm³

3.no. of moles

4.no. of moles

Stoichiometry is related to the whole number ratios

(i) between atoms in chemical formulas and

(ii) between reactants and products in a chemical equation.

Example 1

A mixture containing only aluminium oxide, Al₂O₃, and copper (I) oxide, Cu₂O, weighs 2.02 g. When heated under a stream of hydrogen, only Cu₂O is reduced to metallic copper and steam as follows:

If the residue weighs 1.88 g, what is the percentage by mass of Cu₂O in the mixture?

Solution

mass of Al₂O₃ + Cu₂O = 2.02 g

mass of Al₂O₃ + Cu = 1.88 g (residue comprises both Al₂O₃ + Cu, not just Cu)

mass of oxygen removed = 2.02 – 1.88 = 0.14 g

no. of moles of oxygen atoms = 0.14 ÷ 16 = 0.00875 mol (just consider O, not O₂, according to the formula Cu₂O)

no. of moles of Cu₂O = no. of moles of O = 0.00875 mol (critical step)

mass of Cu₂O = 0.00875 × (63.5 × 2 + 16.0) = 1.25125 g

percentage by mass of

✓ Common mistake: no. of moles of

✓ Comment: no. of moles

Example 2

0.144 g of a binary compound of aluminium and carbon reacts with an excess of water to produce a gas. This gas burns completely in oxygen to form water and 72 cm³ of carbon dioxide only. All measurements are taken at room temperature and pressure. Determine the empirical formula of the binary compound. (1 mole of gas occupies 24 dm³ of volume at r.t.p)

Solution

no. of moles of

no. of moles of C	= no. of moles of CO2 (from the formula, CO2, and the equation, C + O2 → CO2)
	= 0.003 mol

mass of C = 0.003 × 12.0 = 0.036 g

mass of Al = 0.144 – 0.036 = 0.108

Hence, the empirical formula of X is Al₄C₃.

Example 3

Y is an organic iron compound containing only Fe, C and H. When a 1.888 g sample of Y was subjected to complete combustion, 4.46 g of CO₂ and 0.914 g of H₂O were formed. Determine the empirical formula of Y.

Solution

no. of moles of

no. of moles of C	= no. of moles of CO2 (from the stoichiometry of the reaction)
	= 1.0136 × 10^−1 mol

mass of C = 1.0136 × 10⁻¹ × 12.0 = 1.2164 g

no. of moles of

For a given formula of H2O, no. of moles of H	= no. of moles of H2O × 2 (critical step)
	= 5.0778 × 10^−2 × 2
	= 1.0156 × 10^−1 mol

mass of H = 1.0156 × 10⁻¹ × 1.0 = 0.10156 g

Therefore, mass of Fe = 1.888 – 1.2164 – 0.10156 = 0.57004 g

no. of moles of

Hence, the empirical formula of Y is FeC₁₀H₁₀.

Calculations Involving Gases

Avogadro’s Law states that equal volumes of any gases, under the same conditions of temperature and pressure, contain the same number of particles (atoms or molecules).

Molar volume of a gas at s.t.p (0^oC and 1 atmosphere) is 22.4 dm³.
Molar volume of gas at r.t.p (25^oC and 1 atmosphere) is 24.0 dm³.

Volume of gas = molar volume × number of moles

The molecular formula of gaseous hydrocarbo...

Table of contents

• Cover page
• Title page
• Copyright
• About the Authors
• Preface
• Acknowledgments
• Section 1 General and Physical Chemistry
• Section 2 Inorganic Chemistry
• Section 3 Organic Chemistry
• Dr Ernest Wong’s Testimonial
• Index