[ chem module 2 key definitions ]

Question 1

What is the atomic number?

Answer 1

The number of protons an element has.

Question 2

What is an isotope of an element?

Answer 2

An isotope of an element will have the same number of protons and electrons but a different number of neutrons.

Question 3

What is an ion?

Answer 3

An ion is a charged atom which either lost or gained electrons.

Question 4

What is the difference between a cation and anion?

Answer 4

Cation is a positive ion which lost electrons.
Anion is a negative ion which gained electrons.

[Try remember anion as an onion which is bad boo hoo therefore negative]

Question 5

What is the relative isotopic mass?

Answer 5

The mass of an isotope relative to 1/12th the mass of a carbon-12 atom.

Question 6

What is the definition of relative atomic mass?

Answer 6

The weighted mean mass of an atom of an element relative to 1/12th the mass of a carbon-12 atom.

Question 7

How do you calculate the relative atomic mass?

Answer 7

Contribution from isotope x percentage / 100

For example, (75.78x35) + (24.22x37) / 100

Question 8

What is the formulae for an ammonium ion?

Answer 8

NH4+

Question 9

What is the formulae for a hydroxide ion?

Answer 9

OH-

Question 10

What is the formulae for a nitrate ion?

Answer 10

NO3-

Question 11

What is the formulae for a carbonate ion?

Answer 11

CO3 2-

Question 12

What is the formulae for a sulfate ion?

Answer 12

SO4 2-

Question 13

Example question: What is the formulae for zinc chloride?

Answer 13

ZnCl2

Question 14

Example question: What is the formulae for aluminium sulfate?

Answer 14

Al2(SO4)3

Question 15

What is the avogadro constant?

Answer 15

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

6.02x 10^23

Question 16

What are the three mol equations?

Answer 16

Mol: Mass/Mr
Mol: Conc x Vol (dm3)
Mol: Vol/24 (for gases)

Question 17

What is the molecular formulae?

Answer 17

The number of atoms of each element in a molecule.

Question 18

What is the empirical formulae?

Answer 18

The simplest whole number ratio of atoms of each element in a compound.

Question 19

Example question: What is the empirical formulae for C6H12O6

Answer 19

CH2O

Question 20

How do you calculate empirical formulae?

Answer 20

1) Do mass/mol or percentage/mr

2) Find the simplest whole number ratio and divide the smallest whole number

Question 21

Example question: Chemical analysis of a compound gave composition by mass C: 40% H: 6.67% O: 53.33%

Answer 21

C6H12O6

[Ask me if u don’t understand why hehe]

Question 22

What are the water of crystallisation?

Answer 22

The water molecules that are part of a crystalline structure.

Question 23

What does it mean when a Crystal is hydrated?

Answer 23

It contains water molecules.

Question 24

What does it mean when a crystal is anhydrous?

Answer 24

Water molecules are absent.

Question 25

Why do you assume during water of crystallisation experiments?

Answer 25

+All of the water has been lost | +There is no further decomposition

Question 26

What is the ideal gas equation? What does each letter represent and what unit is used?

Answer 26

pV= nRT ``` p: pressure (Pa) V: volume (m3) n: mol R: ideal gas constant (8.31 jmol-1K-1) T: temperature (K which is degrees +273) ```

Question 27

What is the equation for percentage yield?

Answer 27

Percentage yield= Actual yield/Theoretical yield x 100

Question 28

What is atom economy?

Answer 28

The sum of molar masses of desired products/ The molar masses of all products x 100

Question 29

What is the difference between a strong and weak acid?

Answer 29

A strong acid like HCL will completely dissociate (release all H+ ions) wheres a weak acid like CH3COOH will only partially dissociate (release some H+ ions)

Question 30

What is an alakli?

Answer 30

A base that will dissolve in an aqueous solution and release OH- ions

Question 31

What is a salt?

Answer 31

A chemical compound formed when the H+ atom is replaced by a metal. For example sodium chloride (NaCl)

Question 32

What is an acid?

Answer 32

A substance when dissolved in H2O will release hydrogen ions (H+)

Question 33

What is formed when an acid reacts with a metal oxide/hydroxide?

Answer 33

Acid + Metal Oxide/Hydroxide -> Salt + Water

Question 34

Example Question: What is formed when Copper oxide reacts with sulfuric acid? Write both the word and symbol equation with state symbols.

Answer 34

Word: Copper oxide + Sulfuric acid -> Copper Sulphate and Water Symbol: CuO (s) + H2SO4 (aq) -> CuSO4 (aq) + H2O (l)

Question 35

What is formed when acids react with carbonates?

Answer 35

Acid + Carbonate -> Salt + Water + Carbon Dioxide

Question 36

What is an oxidation number?

Answer 36

The number of electrons involved in bonding.

Question 37

What is a standard solution in titrations?

Answer 37

A solution with a known concentration.