4.1 Chem. Reactions & Equations
How many products does a synthesis reaction form?
one single product
What should be used to convert from atoms or molecules --> moles?
Avogadro's Number: 6.022x1023
What is an oxidation number equal to when the atom doesn't holds a charge or a molecule is neutral ?
zero
cathode = more negatively charged
anode = more positively charged
Which type of compound shares electrons, and which is it where electrons are transferred?
Ionic compound = transferred electrons (typically a cation+ & an anion-)
Covalent compound = shared electrons (no charges are demonstrated)
How are chemical reactions classified?
according to the chemicals involved and their behaviors
When calculating the molar mass in a compound, how do you find the mass of an atom?
You look at the atomic mass on the periodic table of elements of that atom.
When referring to REDOX reactions, what is the term we use to describe when an atom has become more positive, and what is the term used to describe when an atom ends up being more negative?
more positive = oxidation (e- lost)
more negative = reduction (e- gained)
Fill in the blank: In an electrochemical cells, the ___________element GIVES up electrons that are transferred to the ___________element that GAINS these electrons.
oxidized, reduced
Which law is ALWAYS followed when balancing chemical equations?
The Law of Conservation of Mass = matter can't be created or destroyed so whatever you have on the reactant side you must have on the product side
Which type of reaction must be predicted using solubility rules?
double displacement
Explain why we use moles when working with atoms?
Because it is easier and more efficient to count by 6.022x23 than atom by atom; since even a spec of a substance can hold millions of atoms.
You have just balanced the elements and charges in BOTH half reactions. Explain the next step in balancing a REDOX reaction.
Balance the electrons in both half reactions by multiplying either half reaction by a number.
What are the units used when calculating molar mass?
g/mol = grams per mole.
What happens during a double displacement reaction?
cations and anions in two compounds trade places
Summarize what a reactivity series is and what is used for.
A series of the most reactive metals to the least reactive metals.
It is used to check if a single-displacement reaction will occur. If it does, then the MORE reactive element replaces the LESS reactive element in a compound.
Calculate the MOLAR MASS of:
Ca(OH)2
40.078 + (16+ 1.01)2 =
40.078 + (17.01)2=
40.078 + 34.02 = 74.089g/mol Ca(OH)2
Determine what was oxidized and what was reduced in the following equation.
Cl2 + 2NaBr ---> 2NaCl + Br2
SHOW YOUR WORK! *
Cl = 0 ---> Cl = -1
Na = +1 ---> Na = +1
Br = +2 ---> Br = 0
Oxid.(LOST e-) = NaBr (ended up more positive
Redu. (GAINED e-) Cl (ended up more negative)
What does the coefficient in front of the chemical symbol mean?
For example.
3Cr2+
it is the number of atoms of that element that exist in the compound.
Define the five types of chemical reactions.
Synthesis reactions = forms a single product from TWO or MORE reactants
Decomposition reactions = forms TWO or more products from a SINGLE reactants
Combustion reactions = substance combines w/ oxygen to form an oxide, & releases thermal energy
Single-displacement reactions = when active elements replace a less active element in a compound
Double-displacement reactions = when ions in two compounds trade places.
Which type of reaction are the following reactions:
Aluminum reacting with zinc chloride to from zinc and aluminum chloride
&
BaCl2 + H2SO4 ---> BaSO4 + 2HCl
single displacement
& double displacement
Calculate the mass in grams of 4.5 moles of C6H12O6
6 mol of C = 12.01g/mol x6 = 72.06
12 mol of H = 1.01g/mol x12 = 12.12
6 mol of O = 16g/mol x6 = 96
72.06 + 12.12 + 96 = 180.18g/mol
(4.5 mol C6H12O6)/1 x (180.18g C6H12O6) /(1molC6H12O6)
= 810.702g ---> 810.70gC6H12O6
Write the half-reactions for the following REDOX reaction.
Si + 2F2 ---> SiF4
Ox: Si ---> Si4+ + 4e-
Red: F2 + 2e- ---> 2F
Name 3 similarities and ONE difference between electrolytic and voltaic cells.
Both types include electrodes (anode & cathode)
Both facilitate transformations between electrical & chemical energy
REDOX reactions occur in both and electrons are transferred from one substance to another.
Voltaic cells, electrons flow spontaneously during the reaction, in an electrolytic cell it is not spontaneous.
What is the difference between the oxidized compound and the oxidizing agent and the reduced compound and the reducing agent?
The oxidizing agent causes oxidation of the other compound by getting reduced.