Chapter 1 - Stoichiometry

Question 0

What is a mole?

Answer 0

Amount of a substance that contains 6.02 x 10^23 particles

Question 1

What is Avogadro’s number?

Answer 1

6.02 x 10^23

Question 2

What is the relative molecular mass?

Answer 2

(Mr)

Mass of a molecule compared to C-12

Question 3

What is the molar mass?

Answer 3

(M)

Mass of 1 mole of any substance in g/mol

Question 4

How do you get mass from moles?

Answer 4

m=nM

Question 5

How do you get number of particles from moles?

Answer 5

N=nL

Question 6

What is the molecular formula?

Answer 6

The number and types of atoms in a molecule

Question 7

What is the empirical formula?

Answer 7

The lowest ratio of number and type of atoms in a compound

Question 8

What is %composition by mass?

Answer 8

The abundance of a substance in a compound by mass

Question 9

How do you find %composition?

Answer 9

1) Formula

2) Experiment

Question 10

What is a word equation?

Answer 10

ie.

solid copper + an aqueous solution of silver (I) nitrate -> solid silver + aqueous copper (II) nitrate

Question 11

What is a balanced chemical equation?

Answer 11

ie.

Cu(s) + 2AgNO3(aq) -> 2Ag(s) + Cu(NO3)2(aq)

Question 12

What are subscripts in chemical equations?

Answer 12

(s) - solid
(l) - melted
(g) - gas
(aq) - dissolved in water
(al) - dissolved in alcohol

Question 13

What is a stoichiometric coefficient?

Answer 13

The coefficient added before a molecule to balance the equation

Question 14

What is an ionic equation?

Answer 14

All aqueous ionic materials break into ions
ie.
Cu(s) + 2Ag(aq) + 2NO3(aq) -> 2Ag(s) + Cu(s) + 2NO3(aq)

Question 15

What is a net ionic equation?

Answer 15

Spectator ions are removed
ie.
Cu(s) + 2Ag(aq) -> 2Ag(s) + Cu(aq)

Question 16

What is a single displacement reaction?

Answer 16

Non-metal: AB + C -> AC + B

Metal: AB + C -> CB + A

Question 17

What is a double displacement reaction?

Answer 17

AB + CD -> CB + AD

Question 18

What is a synthesis reaction?

Answer 18

A + B -> AB

Question 19

What is a decomposition reaction?

Answer 19

AB -> A + B

Catalyst goes under arrow

Question 20

What is a combustion reaction?

Answer 20

Combustion of a fuel produces oxides of elements in the fuel
ie.
CH4 + 2O2 -> CO2 + 2H2O

Question 21

What is theoretical yield?

Answer 21

The max amount predicted by gravimetric stoichiometry

Question 22

What is experimental yield?

Answer 22

The actual amount obtained experimentaly

Question 23

How do you calculate %yield?

Answer 23

%yield = exp/theory x 100%

Question 24

Why do theoretical and experimental yields differ?

Answer 24

1) Poor separation of product
2) Unwanted site reactions
3) Incomplete reaction
4) Transfer and preparation methods
5) (Purity of starting reagents)

Question 25

How do you solve a gravimetric stoichiometry equation?

Answer 25

1) Balance the equation
2) Convert amount to moles: n=m/M or n=M/L
3) Use the equation
4) Convert moles to amounts: m=nM or N=nL

Question 26

What is a limiting reagent?

Answer 26

The reactant that determines the amount of a product (often all used up in the reaction)

Question 27

What is the excess reagent?

Answer 27

The reactant that is left over