Mole Concept and Stoichiometry

Question 1

Formula for moles

Answer 1

Mass÷(mr/ar)

Question 2

Formula for moles in aqueous solution

Answer 2

Concentration x volume ÷ 1000

Question 3

Formula for moles in gases

Answer 3

Vol of gas ÷ 24dm3 or 24000cm3

Question 4

What is Avogadro’s constant

Answer 4

1 mole : 6.02x10^23g

Question 5

How do we change moldm^-3 to gdm^-3

Answer 5

Multiply by ar or mr

Question 6

% by mass

Answer 6

ar x moles of element ÷ mr x 100

Question 7

Define relative atomic mass

Answer 7

Weighted average mass of the different isotopes of an element as compared to 1/12th the mass of a C-12

Question 8

Define relative isotopic mass

Answer 8

It is the mass of one atom of an isotope of an element compared to 1/12th the mass of an atom of C-12

Question 9

Define relative molecular mass

Answer 9

It is the average mass of one molecule of an element or compound compared to 1/12th of the mass of an atom of C-12

Question 10

Define relative formula mass

Answer 10

It is the sum of the relative atomic masses of the element present in one formula unit of the compound

Question 11

Avogadro’s number

Answer 11

6.022 x 10^23g