THE MOLE CONCEPT

HAVE YOU EVER WONDERED HOW MANY STARS ARE THERE IN THE SKY?

CAN YOU COUNT ALL THE STARS?

How about such as tablespoon of sugar or a tablespoon of salt?

How will you determine the number of particles in a tablespoon of salt?

Is the number of particles in a tablespoon of sugar the same as the number of particles in a tablespoon of salt?

AMEDEO AVOGADRO

Lorenzo Romano Amedeo Carlo Avogadro

di Quaregna e di Cerreto,

Count of Quaregna and Cerreto

was an Italian scientist. He is most noted for his contributions to molecular theory,

including what is known as Avogadro's law.

In tribute to him, the number of elementary

entities (atoms, molecules, ions or other particles) in 1 mole of a

substance,6.02214179(30)×1023

is known as the Avogadro constant.

WHICH HAS A GREATER

NUMBER OF PARTICLES, ONE

MOLE OF COTTON OR ONE MOLE OF SALT?

Question:

ANSWER:

One mole of cotton has the same number of particles as one mole of salt.

One mole of an element contains the same number of atoms as a mole of any other element.

1 M of a given element = 1 M of other elements

1 mole of a compound = 1 mole of other compounds

QUESTION:

How many particles are

there in two moles of monosodium

glutamate, vetsin?

ANSWER:

1 mole = 6.02 ×1023

Multiply 2 by Avogadro’s number.

LET’S TRY THIS!

1. Atomic mass of C?

2. Atomic masses of H and O?

3. Atomic masses of Na and Cl?

One mole of any substance contains the

same number of particles.

What about the mass of a mole of a substance?

Is it same for all substances?

The mass of an element or compound depends on the

mass of its particles.

Therefore, one mole of hydrogen has a mass

dependent on it atomic mass. - MOLAR MASS

MOLAR MASS- the mass in grams that is numerically equal to the atomic mass. The unit of molar mass is grams / mole (g/mol).

WHAT IS THE ATOMIC MASS OF CARBON?

Answer: 12.01 amu

What is the molar mass of carbon?The molar mass of carbon is

12.01 g.

How many atoms are I 12.01g of carbon?

6.022 x 10^23 atoms

EXERCISE:

The atomic mass of oxygen is _______. Its molar mass is _____________. There are ______ atoms found in ________ g of oxygen.

The atomic mass of sodium is _________. Each mole of sodium has a mass of ______. Every ______ g of sodium has _______ atoms.

HOW MANY MOLES ARE THERE IN 70.9 G OF CHLORINE?

Number of moles Cl = given mass

molar mas = 70.9 g 35.45 g/mol = 2 molTo get the number of moles of a

substance:Number of moles = given mass

molar mass

EXERCISES:

1. How many moles are there in 6.05 g of carbon?

2. How many moles are there in 46.00 g of sodium?

HOW MANY NUMBER OF MOLES IN 36.04 G OF WATER?

1. Find the molar mass of water.a. Multiply the atomic mass of H by 2

and that of O by 1.

H = 2 x 1.008 = 2.016O = 1 x 16.00 = 16.00

18.016 or 18.02

Number of moles (H2O) = 36.04 g 18.02 g/mol

= 2.0 mol

Let’s See What You Have Learned

Α. Determine the molar masses of the following:1. acetic acid (CH3COOH)2. agua oxigenada (H2O2)3. ammonia (NH3)

Β. Determine the number of moles in1. 120.0 g of acetic acid2. 17.0 g of agua oxigenada3. 51.0 g of ammonia

Let’s Remember!

♦ The mole is a unit for counting particles in a given mass of a substance. Each mole of a substance is made up of 6.022 × 1023 particles.

♦ The molar mass of a substance is the mass in grams that is numerically equal to the atomic mass or formula mass of the substance.

ANSWERS: