3.2.1 The Mole and Avogadro's Number

Question 1

The Mole and Avogadro’s Number

Answer 1

• The mole is a unit of measure that connects the atomic-molecular world with the macroscopic world.
• Avogadro’s number helps to connect the periodic table with things that can be physically measured.

Question 2

mole and conversion factors

Answer 2

• Atoms and molecules are far too tiny to measure individually. The mole (abbreviated mol) is the collective unit used to measure numbers of things
• A mole is defined to be the number of things good to the number, or atoms present in exactly 12 grams of carbon-12 (12C).
• 12C was chosen as the standard partly because it is the first element in the periodic table whose mass may be conveniently measured.
• Avogadro’s number, 6.022 x 10^23, represents the number of units in a mole.
• Conversion factors are factors of one relating the same quantity between two systems of units. They are used to convert measurements from one set of units to another. Thus, one mole of fluorine atoms is defined to be 6.022 x 10^23 atoms of fluorine.

Question 3

How many atoms of uranium are there in 7.11 millimoles of this substance?

Answer 3

4.28 × 10^21 atoms

Question 4

Give the total number of atoms of each element in 0.50 mole of the compound TNT, or trinitrotoluene: C7H5N3O6.

Answer 4

2. 1 × 10^24 atoms C
3. 5 × 10^24 atoms H
4. 0 × 10^23 atoms N
5. 8 × 10^24 atoms O

Question 5

How many atoms of hydrogen, sulfur, and oxygen are in 1.00 mol of H2SO4?

Answer 5

1. 20 × 10^24 hydrogen;
2. 02 × 10^23 sulfur;
3. 41 × 10^24 oxygen

Question 6

How many moles are represented by 3.75 × 10^21 atoms of iron?

Answer 6

6.23 × 10^−3 moles Fe

Question 7

A sample of Au is found to contain 9.7 × 10^23 atoms of Au. How many moles of Au atoms are in the sample?

Answer 7

1.6 moles

Question 8

One reason carbon-12 (12C) is used as a basis for defining a mole is because ________

Answer 8

carbon-12 is the first solid element which is stable in the presence of oxygen.

Question 9

How many molecules of carbon dioxide are found in 2.50 moles of carbon dioxide?

Answer 9

1.51 × 10^24 molecules

Question 10

What is the total number of atoms of hydrogen in 1.00 mole of the compound C10H11NFe?

Answer 10

6.62 × 10^24 atoms of hydrogen

Question 11

How many moles of N2O3 are there in 4.66 × 10^27 molecules of this substance?

Answer 11

7.74 × 10^3 moles

Question 12

How many atoms are contained in 1.00 mole of water?

Answer 12

18.0 × 10^23 atoms