Chem. Reactions
How many products does a synthesis reaction form?
one single product (Ag + Cl --> AgCl)
What number should be used to convert from atoms or molecules --> moles?
Avogadro's Number: 6.022x1023
What is an oxidation number for each oxygen in the diatomic molecule O2?
zero
How many moles of oxygen gas are required to completely burn 4 moles of methanol (CH3OH)?
CH3OH + O2 --> CO2 + H2O
2CH3OH + 3O2 gives 2CO2 + 4H2O
6 moles of O2 are required
Which type of reaction is this?
HCl (aq) + NaOH (aq) --> H2O (l) + NaCl (aq)
Acid/Base, Redox, or Precipitation?
Acid/Base
How are chemical reactions classified?
according to the number of chemicals involved and their behaviors
What mass (i.e. how many grams) would 10 moles of H2 be?
10 moles x 2.0 grams/mole = 20 grams H2
When referring to REDOX reactions, what is the term we use to describe when an atom has become more positive or lost electrons?
more positive = OXIDATION (e- lost)
A volatile liquid is placed in a container by itself. A pressure gauge shows that the gas pressure in container is increasing while temperature remains the same and the some liquid remains. What type of change is this?
Physical or Chemical?
Physical (evaporation is occurring)
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 or PRECIPITATION reaction
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.
Which is limiting reactant if 3 moles of Cu are added to 3 moles of AlCl3?
Cu + AlCl3 --> Al + CuCl2
Balance 3 Cu + 2 AlCl3 --> 2 Al + 3 CuCl2
Cu is limiting! There is one extra mole of AlCl3
What is molarity of 10 mL a monoprotic acid if it is titrated by 20 mL of 1.0 M NaOH
M x V = M x V
M x 10 mL = 1.0 M x 20 mL
Molarity = 2.0 M acid
Summarize what a reactivity series of metals is and what is used for in reactions.
A list 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
40.08 + (16 + 1.01) x 2 =
40.08 + (17.01) x 2=
40.08 + 34.02 = 74.1 g/mol Ca(OH)2
Determine what element was oxidized and what was reduced in the following equation.
Cl2 + 2NaBr ---> 2NaCl + Br2
Cl = 0 ---> Cl = -1
Br = +2 ---> Br = 0
Oxid.(LOST e-) = NaBr (ended up more positive)
Red. (GAINED e-) Cl (ended up more negative)
What does the coefficient in front of the chemical symbol mean?
For example: 3 Cr2+
it is the number of atoms of that element that exist in the compound.
What is the oxidation number of Nitrogen (N atom) in Nitrate (NO3)-1?
N = +5
O= -2 so 3x O = -6, but NO3 adds up to -1
Which type of reaction is the following:
BaCl2 (aq) + Na2SO4 (aq) ---> BaSO4 (s) + 2NaCl (aq)
double (dis)replacement or PRECIPITATION!
Calculate the mass in grams of 4.5 moles of C6H12O6
6 mol of C = 12.01g/mol x6 = 72.1
12 mol of H = 1.01g/mol x12 = 12.1
6 mol of O = 16g/mol x6 = 96
72.1 + 12.1 + 96 = 180.2g/mol
(4.5 mol C6H12O6) x (180.2g/mole C6H12O6)
= 810.9g
What is the Oxidation half-reaction for the following REDOX reaction.
Si + 2F2 ---> SiF4
Ox: Si 0 ---> Si 4+ + 4e-
What is the formula of the precipitate formed when ammonium sulfate (NH4SO4) solution reacts with strontium nitrate (Sr(NO3)2) solution?
SrSO4
What is the only letter of the alphabet that DOESN'T appear on the periodic table?
J (or Q is also acceptable)