Reactivity 2.1

Question 1

What do chemical reactions show about products and reactants in a reaction?

Answer 1

The ratio

Question 2

How does the balancing of a chemical equation relate to the Law of Conservation of Mass?

Answer 2

No matter can be created or destroyed, so the chemical equations must be balanced i.e. atoms in reactants = atoms in products

Question 3

Reactants

Answer 3

Elements/compounds consumed in a chemical reaction

Question 4

Products

Answer 4

Elements/compounds produced by a chemical equation

Question 5

When is a chemical equation balanced?

Answer 5

When atoms in reactants = atoms in products

Question 6

Steps for balancing a chemical reaction

Answer 6

Word equation, unbalanced chemical equation, balancing, symbols of state

Question 7

What is a precipitate?

Answer 7

An insoluble ionic compound

Question 8

Ionic compounds consisting of these ions are generally soluble (no exceptions)

Answer 8

Na+
K+
NH4+
NO3-
CH3COO-

Question 9

Exceptions to ionic compounds containing ions of Cl-, Br-, I- being generally soluble

Answer 9

Ag+
Pb2+

Question 10

Exceptions to ionic compounds consisting of ions of SO42-, Cr2O72- being generally soluble

Answer 10

Pb2+
Ba2+
Ag+
Ca2+

Question 11

Exceptions to ionic compounds containing CO32-, PO43- and S2- being generally insoluble

Answer 11

Na+
K+
NH4+

Question 12

Exceptions to ionic compounds containing OH- being generally insoluble

Answer 12

Na+
K+
NH4+
Ba2+
Ca2+

Question 13

Ionic equation

Answer 13

Balanced equation which only contains species that underwent change during the chemical reactions i.e. only includes species that underwent bond breaking and/or bond making

Question 14

Spectator ions

Answer 14

Ions (liquid or aqueous) that remain unchanged during the reaction

Question 15

What happens to spectator ions in an ionic equation?

Answer 15

Omitted

Question 16

In a precipitation reaction, which ions are included in the ionic equation?

Answer 16

Ions that eventually end up in precipitate

Question 17

Steps for writing ionic equations

Answer 17

Write a full chemical equation for the reaction

Show the individual ions for any species that will be present as separate ions (liquid/ aqueous ionic compounds and aqueous acids)

Eliminate any spectator ions

Write the ionic equation

Question 18

Which ions are written as separate ions in an ionic equation?

Answer 18

Liquid and aqueous ionic compounds

Aqueous acids

Question 19

Element + oxygen ->

Answer 19

Elemental oxide

Question 20

Hydrocarbon + oxygen ->

Answer 20

Carbon dioxide and water

Question 21

Complete combustion

Answer 21

Hydrocarbon + oxygen -> carbon dioxide + water

Question 22

Reactive metal + water ->

Answer 22

Metal hydroxide + hydrogen

Question 23

Acid + metal ->

Answer 23

Salt + hydrogen

Question 24

Acid + base ->

Answer 24

Salt and water

Question 25

Neutralisation reaction

Answer 25

Acid + base -> salt + water

Question 26

Acid + metal carbonate ->

Answer 26

Salt + carbon dioxide + water

Question 27

Acid + metal hydrogen carbonate ->

Answer 27

Salt + carbon dioxide + water

Question 28

Which non-metals come in pairs?

Answer 28

N O F Cl Be I

Question 29

Precipitation reaction reactants

Answer 29

Two aqueous solutions (ions swap)

Question 30

What can ionic equations be written for?

Answer 30

Ionisation of acids in aqueous solutions Precipitation reactions

Question 31

For a substance to dissociate into ions, it must

Answer 31

Be ionic or dissociate in water

Question 32

Mass-mass stoichiometry

Answer 32

Write a balanced chemical equation for the reaction Convert known mass to moles Write the required mole ratio Use the mole ratio to calculate the moles of the unknown reactant/product Convert back to mass of unknown

Question 33

Mole ratio for mass-mass stoichiometry

Answer 33

n(unknown) / n(known) = coefficient (unknown) / coefficient (known)

Question 35

What equations can be used for mole-mole stoichiometry?

Answer 35

n = m / M n = PV / RT n = c x V n = V / Vm (at STP)

Question 36

Avogardo’s law

Answer 36

Equal volumes of all gases measured under the same conditions of temperature and pressure contain equal numbers of molecules

Question 37

What does Avogardo’s law mean in relation to stoichiometry?

Answer 37

Volume-volume stoichiometry can occur, with a volume ratio found in the same way as the mole ratio

Question 38

What are the assumptions when doing Volume-Volume stoichiometry?

Answer 38

Pressure and temperature are the same

Question 39

What is the limiting reagent?

Answer 39

Reactant that it is totally consumed when the reaction is completed

Question 40

What does the limiting reactant determine?

Answer 40

The theoretical amount of product produced

Question 41

How to identify the limiting reactant

Answer 41

Balanced chemical equation for the reaction Identify what you know about each reactant Convert known quantities to moles Divide the moles of each reactant by the corresponding coefficient Smallest value is the limiting reactant. Largest value = in excess

Question 41

How to predict quantity of product from limiting reactant

Answer 41

Use mole ratio of n(unknown)/n(known) = coefficient (unknown) / coefficient (known)

Question 42

Theoretical yield

Answer 42

Amount of product theoretically produced

Question 43

Predicting quantity of the reactant in excess that will remain unreacted

Answer 43

n(excess)react / n(limiting) = coefficient excess / coefficient minting Then, n(excess)unreacted = n(excess)initial - n(excess)react

Question 44

Percentage yield

Answer 44

Experimental yield / theoretical yield. X 100%

Question 45

Atom economy

Answer 45

Molar mass of desired product / molar mass of all reactants. X 100%

Question 45

Green chemistry

Answer 45

An approach to chemical research and engineering that seeks to minimise the production and release into the environment of hazardous substances