Reduction of Copper(II) oxide by Hydrogen

Hydrogen is more reactive than copper. Copper(II) oxide is reduced to copper by hydrogen. The same reaction is used to determine empirical formula of copper(II) oxide in Chapter 3 : Chemical Formulae & Equation.

Empirical Formula and Molecular Formula

Avogadro Constant

Molecular Formula, Empirical Formula and Structural Formula

What is a mole (Animation)

Avogadro Constant & Amedeo Avogadro

Avogadro Constant : 

(Definition : Number of particles in 1 mole of a substance )

is named after

 Amedeo Carlo Avogadro(1776 - 1856)

for his great contribution towards chemistry.

The Meaning of Relative Atomic Mass

What is the meaning of Relative Atomic Mass of an element?

A carbon-12 atom is chosen as a reference. Carbon-12 is assigned a mass of exactly 12 unit.
Mass of an atom of an element when compared with 1/12 of mass of a carbon-12 atom.

Number of Atoms & Number of Molecules

Which of the following substance contains 1.204 x 10²⁴ atoms?

A  1 mol of nitrogen gas
B  1 mol of ammonia
C  1 mol of water
D  1 mol of argon

Many of my students choose the wrong answer in the current topical test.

1 mol of nitrogen gas consists of 1 x 6.02 x 10²³ molecules. 

Number of atoms in 1 mol of nitrogen gas is 2 x 6.02 x 10²³ .
(Each nitrogen, N₂ molecule consists of 2 nitrogen atoms)

1 mol of ammonia consists of 1 x 6.02 x 10²³ molecules

Number of atoms in 1 mol of ammonia gas is 4 x 6.02 x 10^23.
(Each ammonia, NH₃ molecule consists of 4  atoms) 

1 mol of water consists of 1 x 6.02 x 10²³ molecules

Number of atoms in 1 mol of water is 3 x 6.02 x 10²³
(Each water, H2O molecule consists of 3 atoms) 

1 mol of argon consistss of 1 x 6.02 x 10²³ atoms. 


The correct answer : A

How to Determine Empirical Formula of Magnesium Oxide

Creative Way of Remembering Chemical Formulae of Ions

I found out this piece of note recently. The student is trying to remember the chemical formulae of ions. The method used is using mneumonics.  Menumonics is one of the ways that can dramatically improve our memory! If you have other interesting mneumonics, do share with me!

Volume of Gas

1 mol of any gases, as you name it, oxygen gas, helium gas, hydrogen gas, neon gas, etc.... occupy the same volume in the room condition.

This concept is known as molar volume at room condition, which is 24 dm³ mol^-1.

Moles

 

Concept of moles is an important concepts in chemistry. Students learn the basic concepts in Chapter 3 Chemical Formulae and Equation during form 4. Later, they relate the moles concepts with molarity of a solution in Chapter 7 Acids and Bases and Chapter 8 Salts.

 

During form 5, students are expected to apply the concept well in various numerical problems in Chapter 1 Rate of Reaction, Chapter 4 Thermochemistry.

Some common wrong concepts that I have come across:

• students thought that the moles is the same with molarity.
• they thought that volume refer for both solution and gas.

Plese my dear students, please study the relationship above thoroughly. Whenever come across any question related to this concepts, understand the questions and substitute the value given in the equation correctly.

All About Moles

Let's start a journey of the mole....

Any relationship with the mole with the Avogadro Constant, Mass and Volume of Gases?