Module 2 - chapter 2 and 3 key terms

Question 1

Atomic (proton) number Z

Answer 1

Number of protons in the nucleus

Question 2

Mass (nucleon) number A

Answer 2

Number of particles (protons and neutrons) in the nucleus.

Question 3

Isotopes

Answer 3

Atoms of the same element with different numbers of neutrons but the same number of protons, hence they have different masses.

Question 4

Ions

Answer 4

Positively or negatively charged atoms or (covalently bonded) groups of atoms (a molecular ion). Formed by the loss or gain of one or more electrons from an atom or group of atoms

Question 5

Relative isotopic mass

Answer 5

(RIM) the mass of an atom of an isotope compared with 1/12th of the mass of carbon-12.

Question 6

Relative atomic mass

Answer 6

Ar, the weighted mean mass of an atom of an element compared with 1/12th of the mass of carbon-12.

Question 7

Relative molecular mass

Answer 7

Mr - the weighted mean mass of a MOLECULE compared with 1/12th of the mass of an atom of carbon-12 (only applies to simple covalently bonded molecule like O2 or CO2)

Question 8

Relative formula mass

Answer 8

the weighted mean mass of a formula unit compared to the mass of an atom of carbon-12
RFM can apply to ionic substances as these occur as giant lattices

Question 9

Empirical formula

Answer 9

Shows the simplest ratio of atoms in a compound.

Question 10

Concentration

Answer 10

The concentration of a solution is the amount of solute (in mol) dissolved per 1 dm³ (1000cm³) of solution.

Question 11

Dilute

Answer 11

Process of decreasing the concentration of a solute in solution. We add more solvent without adding more solute, therefore reducing the concentration.

Question 12

Theoretical yield

Answer 12

The maximum possible amount of product.

Question 13

Percentage yield

Answer 13

(actual yield / theoretical yield ) x 100

Question 14

Limiting reagent

Answer 14

The reactant that is not in excess will be completely used up first and stop the reaction, this is the limiting reagent.

Question 15

Atom economy

Answer 15

The atom economy of a chemical reaction is a measure of how well atoms have been utilised.

Question 16

Avagadro’s constant

Answer 16

6.02 x 10^23

Question 17

Molecular Formula

Answer 17

The number of atoms of each element in a molecule

Question 18

Hydrated Salts

Answer 18

Many coloured crystals are hydrated - water molecules are part of their crystalline structure.

Question 19

Water of crystallisation

Answer 19

Is the water molecules that are part of the crystalline structure of hydrated salts.

Question 20

Standard solution

Answer 20

Is a solution of known concentration.

Question 21

Molar gas volume

Answer 21

Is the volume of per mole of gas molecules at a stated temperature and pressure.

Question 22

Stoichiometry

Answer 22

In a balanced equation, the balancing numbers give the ratio of the amount, in moles, of each substance.

Question 23

Binary compound

Answer 23

A compound that contains two elements only.