Amount Of Subtance

Question 1

Relative atomic mass

Answer 1

The relative atomic mass is the average mass of atom (taking into account it’s naturally occurring isotopes) of an element relative to 1/12 of the relative atomic mass of a carbon 12 atom.

Question 2

Relative molecular mass

Answer 2

The relative molecular mass MR of a substance is the mass of that molecule compared to 1/12 of the relative atomic mass of an atom of carbon 12.

Question 3

When do we use the term relative formula mass?

Answer 3

The term relative formula mass is used for ionic compounds because they don’t exist as molecules. However, this has the same symbol as MR.

Question 4

The Avogadro constant

Answer 4

The Avogadro constant or Avogadro number is the number of atoms in 12 g of carbon 12.

Question 5

What is Avogadro’s constant?

Answer 5

6.022×10 to the power of 23

Question 6

What is a mole?

Answer 6

The amount of substance that contains 6.022×10 to the 23 particles is called a mole.

Question 7

Ideal gas equation

Answer 7

pv=nRT

Question 8

Give the units of pV=nRT

Answer 8

P. Pressure: Pa
V volume: m^3
n number of moles
R gas constant : J K^-1 mol ^-1
T temperature: K

Question 9

Empirical formula

Answer 9

The empirical formula is the formula that represents the simplest whole number ratio of atoms of each element present in a compound.

Question 10

Molecular formula

Answer 10

The molecular formula gives the actual number of atoms of each element in one mole of the compound.

Question 11

Atom economy

Answer 11

% atom economy = mass of desired product / total mass of reactants x 100

Question 12

Percentage yield

Answer 12

Actual yield/theoretical yield x 100