Module 2 and 3

Question 1

Definition of relative isotopic mass

Answer 1

It’s mass compared to 1/12th of the mass of an atom of carbon-12

Question 2

Definition of relative atomic mass

Answer 2

Weighted mean mass of an element compared to 1/12th of the mass of an atom of carbon-12

Question 3

How does a mass spectrometer work? (half-life ref.???)

Answer 3

1. Sample place in it
2. Vapourised, then ionised to form positive ions (electrons lost)
3. Ions are accelerated. Lighter ions move more quickly through tube
   and isotopes are separated
4. Ions detected on a mass spectrum as m/z. Ions added to signal, greater abundance greater signal.

Question 4

What are binary compounds and how to name them?

Answer 4

Compound of two elements. Change second element ending to -ide

Question 5

Draw out the table for polyatomic ions and write in all the common ones (including charges).

Question 6

What is Avogadro Constant (definition)?

Answer 6

The number of particles in each mole of carbon-12.

Question 7

Definition of molecular formula?

Answer 7

The number of atoms of each element in a molecule

Question 8

Definition of empirical formula?

Answer 8

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

Question 9

What is the water of crystallisation?

Answer 9

The water in a hydrated salt

Question 10

How to work out formula for hydrated salt?

Answer 10

Mass of anhydrous salt and crucible - mass of crucible,
mol of the salt
mass of hydrated salt - anhydrous salt, mol of h2o and compare
(include the dot inbetween)

Question 11

What assumptions are made during the hydrated salt experiment?

Answer 11

1-All water has been lost (hard too know if colours of hydrogous and anhydrous are similar), so heat solution till constant mass
2- No further decomposition is occurring

Question 12

Assumptions for molecules making up ideal gas?

Answer 12

-Random motion
-No intermolecular forces
-Elastic collisions