3.1.2 Amount of substance

Question 1

Avogadro’s Constant (Nₐ):

Answer 1

6.02 x 10²³

Question 2

Moles [2]:

Answer 2

• The unit of amount of substance

- One mole is equal to 6.02 x 10²³ particles

Question 3

Number of moles =

Answer 3

molecular mass (Mᵣ)

Question 4

Relative atomic mass(Aᵣ) [definition]:

Answer 4

The average mass of an atom compared with 1/12 the mass of an atom

Question 5

Relative molecular mass(Mᵣ) [definition]:

Answer 5

The average mass of a molecule compared with 12g of a carbon 12 atom

Question 6

What is the standard reference point in chemistry?

Answer 6

Carbon 12

Question 7

Avogadro’s Constant [info]:

Answer 7

One mol of any substance contains 6.02 x 10²³identical atoms/molecules/ions of that substance

Question 8

Moles and concentration:

Number of moles =

Answer 8

Concentration x volume (dm³)

Question 9

Number of particles =

Answer 9

Avogadro’s constant (Nₐ) x Number of moles

Question 10

Molecular formula [definition]:

Answer 10

The number of atoms of each element in a molecule

Question 11

Empirical formula [definition]:

Answer 11

The smallest whole-number ratio of atoms of each element in a compound

Question 12

The ideal gas equation:

Answer 12

pV=nRT

Question 13

ideal gas equation meanings [5]:

Answer 13

p= pressure in Pa
V= volume in M³
n= mol
R= the gas constant (8.31 J K⁻¹ mol⁻¹
t= temperature in K

Question 14

°C —> K =

Answer 14

+273

Question 15

Mole [definition]:

Answer 15

The amount of substance that contains the same number of particles as there are in 12g of carbon 12

Question 16

Standard solution [definition]:

Answer 16

A solution of known concentration

Question 17

How do you make a standard solution?

Answer 17

-They are made by dissolving an accurately weighed, mass of solid in a volume of solvent using a volumetric flask

Question 18

Volumetric flask [description]:

Answer 18

It has a thin neck which is marked with a line so it can be filled accurately to its correct capacity

Question 19

Concentration [definition]:

Answer 19

A measure of how much solute is dissolved per unit solvent

Question 20

Concentration [equation]:

Answer 20

Concentration = amount of solute (mol)
(mol/dm³) ————————————
. volume of solvent (dm³)

Question 21

Concentration [equation for cm³]:

Answer 21

Concentration = amount of solute x 1000 (mol)
(mol/dm³) ————————————
. volume of solvent (cm³)

Question 22

Percentage yield [definition]:

Answer 22

Percentage of how much product was actually made compared with the amount of product that was expected

Question 23

Percentage yield [equation]:`

Answer 23

Percentage yield = Actual yield
(%) —————————– x 100
. Theoretical yield

Question 24

Atom economy [definiton]:

Answer 24

The percentage of the total mass of reactants that can be converted into desired product

Question 25

Atom economy [equation]:

Answer 25

mass of desired product
————————————- x 100
total mass of reactants