Chapter 9

Question 1

What is the relative atomic mass (Ar) of an atom?

Answer 1

average mass of one atom of the element
________________________________
1/12 mass of an atom of carbon-12

Question 2

What is the relative molecular mass (Mr) of a molecular substance?

Answer 2

average mass of one molecule of an element or a compound
_______________________________________________
1/12 mass of an atom of carbon-12

Question 3

How many particles are there in one mole of any substance?
What is this value called?

Answer 3

6 x 10^23 particles,
this value is called Avogadro’s constant/number.

Question 4

What does number of moles equal to?

Answer 4

number of particles
________________
6 x 10^23

Question 5

What does the number of moles of an element equal to? (Hint: equation)

Answer 5

mass of the element in g
__________________________
molar mass of the element in g/mol

Question 6

What does the number of moles of a molecular substance equal to?

Answer 6

mass of the substance in g
_____________________________
molar mass of the substance in g/mol

Question 7

What does the number of moles of an ionic compound equal to?

Answer 7

mass of the compound in g
_____________________________
molar mass of the compound in g/mol

Question 8

How do you calculate percentage by mass of an element in a compound?

Answer 8

Ar of the element x number of atoms of the element in the formula
____________________________________________________ x 100%
Mr of the compound

Question 9

How much volume does a mole of any gas occupy at r.t.p.? What is it called?

Answer 9

24 dm^3 (24 000cm^3),
this is called the molar volume of a gas.

Question 10

What does number of moles of gas equal to?

Answer 10

mass of gas in g
____________________
molar mass of gas in g/mol

OR

volume of gas in cm^3 at r.t.p.
_______________________
24 000cm^3

Question 11

What is concentration of a solution?

Answer 11

The concentration of a solution is given by the amount of a solute dissolved in a unit volume of the solution.

Question 12

How do you calculate concentration in g/dm^3?

Answer 12

mass of solute in g
____________________
volume of solution in dm^3

Question 13

How do you calculate concentration in mol/dm^3?

Answer 13

number of moles of solute
_____________________
volume of solution in dm^3

OR

concentration in g/dm^3
_______________________
molar mass of solute in g/mol