Atoms, Molecules & Stoichiometry

Question 1

What is the definition of relative atomic structure

Answer 1

Ar= average mass of an atom x12 / mass of one atom of carbon-12

Question 2

What is the definition of relative isotopic mass?

Answer 2

Mass of isotope/mass of one atom of carbon-12

Question 3

Definition of molecular mass or relative formula mass(ions)?

Answer 3

Mass of one molecule x12/mass of one atom of carbon-12

Question 4

what is the definition of % by mass?

Answer 4

Atomic mass x no. Of moles of element in cpd/molar mass of cpd x100

Question 5

What is the empirical formula?

Answer 5

Simplest whole-number ratio of the number of atoms of each element in a compound.

Question 6

How to work out molecular formulae?

Answer 6

1. Work out relative mass of empirical formula
2. Calculate how many empirical formula units in one molecule
   (relative molecular mass(given)/relative mass of empirical formula)
3. Multiply empirical by answer from calculation.

Question 7

What is the formula for combustion data?

Answer 7

CxHy + (x+y/4)O2 —> xCO2 + y/2 H2O

Question 8

What is the definition for mole?

Answer 8

One mole is the amount of substance that contains as many particles as there are atoms in exactly 12g of carbon-12.

Question 9

What is the formula to find concentration?

Answer 9

Conc (gdm-3) = mass/vol dm3

Conc (moldm-3) = mol/vol dm3