reactions and stoichiometry

Question 1

avogadro’s number

Answer 1

there are 6.02E23 molecules in a mole

Question 2

molar mass units

Answer 2

g/mol

Question 3

molecular formula

Answer 3

ex: SF6
- gives the number of atoms of each element in a compund

Question 4

empirical formula

Answer 4

reduced form of molecular formula
ex: glucose empiracle formula is C(h2O)

Question 5

percent composition by mass

Answer 5

mass of element/ mass of compound

Question 6

problem situation: find the empirical formula for a compound that is 54% carbon, 9% H and 36% oxygen

Answer 6

assume 100 grams
54g/ 12 = 4.5 m carbon
9 mol hydrogen
36/16 o = 2.25 o
C2H4O
** to get number of each atom, divide each by the smallest amount of moles

Question 7

chemical reaction

Answer 7

one or more chemical species are converted into one or more chemically different species
- bond breaking and reforming
- atoms themselves do not change

Question 8

phase changes

Answer 8

physical process, not chemical and is reversible

Question 9

reaction types on the mcat

Answer 9

synthesis
decomposition
single displacement
double displacement
neutralization
combustion
oxidation reduction
redox

Question 10

synthesis reaction (combustion)

Answer 10

two or more reactants combine to form 1 product
A + B –> AB

Question 11

decomposition rections

Answer 11

reverse of synthesis reactions
breakdown of a reactant into two smaller products
AB –> A+B
ENDOTHERMIC

Question 12

breaking of bonds is typically (endo/exothermic)?

Answer 12

endothermic
-requires energy

Question 13

displacement reaction

Answer 13

one element or gropu replaces another within a compound
- if only 1 group changes : single
- 2 groups exchange : double

Question 14

single displacement formula

Answer 14

A + BC –> B + AC
2K + ZNCl3–> 2KCl + Zn

Question 15

what species typically replaces in a double displacement

Answer 15

halogens and metals

Question 16

methathesis

Answer 16

double replacement reaction when an insoluble product is formed

Question 17

neutralization reaction

Answer 17

an acid and base react with eachother to form water and a salt
HCl + NaOH –> H2O + NaCl

Question 18

combustion reaction

Answer 18

compound burns in the presence of elemental oxygen, non oxygen is burned and turned into fuel
- highly exothermic reacitons
c3h8 +o2 –> co2 + h2o

Question 19

real life examples of combustion reactions

Answer 19

organic compounds of hydrogen and carbon are burned and produce carbon diozide and water

Question 20

products of combustion reaction

Answer 20

h2o and co2
- very exothermic

Question 21

oxidation reduction reactions

Answer 21

transfer of e- from one species to another
- both reactants experience a change in oxidation state

Question 22

oxidation number

Answer 22

the charge that atom would have if the compound were composed of ions

Question 23

limiting reagent

Answer 23

the lesser reactant that determines how much of the product can be formed
- determines amount of product
- reacts completely

Question 24

non-limiting reagent

Answer 24

in excess, does not determine amount of product formed

Question 25

how is the limiting reactant identified

Answer 25

using stoichiometry, calculate the amount of product made from each starting reactant and which ever one is less (in moles), is the limiting reactant
- must measure same product
- remember to balance equations

Question 26

percent yield equation

Answer 26

actual mass/ theoretical mass x 100

Question 27

alkali metals always have an oxidation number of what?

Answer 27

1+

Question 28

alkali earth metals always have an oxidation number of what

Answer 28

2+

Question 29

flourine oxidation number

Answer 29

1-

Question 30

when does hydrogen not have an oxidation state of 1+

Answer 30

naH and liah4

Question 31

oxygen usual oxidation numnber

Answer 31

2-