Module 14

Question 1

Oxidation Numbers

Answer 1

Ex) In H2O, O is in oxidation state -2. O controls 2 more valence electrons than it usually does in pure oxygen
- Other hand - H iin H2O has oxidation state +1. H controls 1 fewer valence electrons than in pure hydrogen

Question 2

Assigning Oxidation State

Answer 2

1. Determine if atom is an atomic ion. If so, oxidation state is equal to its charge
2. If atom is in a molecule made of its same type of element, then oxidation state is 0.
3. If an atom of certain main group element, it might prefer a particular oxidation state
4. Atoms in a molecule or polyatomic ion all add up to total charge. Ex) all atoms’ oxidations states in CO3^2- must add up to -2. C = +4, and 3O = 3(-2). +4 -6 = -2

Question 3

Bronsted Lowry Base

Answer 3

accepts proton

Question 4

Bronsted Lowry Acid

Answer 4

gives proton

Question 5

Oxidation

Answer 5

Loss of Electrons

Question 6

Reduction

Answer 6

Gain of Electrons

Question 7

LEO means GER

Answer 7

Zn^2 + I^1- -> ZnI2
Zn loses 2 electrons to form Zn^2+ cations, while I must gain 1 electron to form 1^- anions.
Zn is oxidized, I is reduced

Question 8

Reducing agent

Answer 8

contains atom being oxidized

Question 9

Oxidizing agent

Answer 9

contains atom being reduced

Question 10

Acid double displacement reaction that evolve to gas

Answer 10

• Carbonates + acid = salt (carbonate cation + acid anion) + CO2 gas + water
• Sulitfe(SO3^2-) + acids = salt (ssulfite cation + acid anion) + SO2 gas + H2O
• Sulfides + acids = salt (ssulfide cation + acid anion) + H2S gas + H2O

Question 11

Calculating pH of strong acid soln

Answer 11

1. Write the reaction
2. As it’s a strong acid, ALL acid will react
   3.Calculate initial moles of acid
3. Calculate moles of H3O produced (1 mol H3O for every 1 mol HA)
   5.Calculate molarity of H3O+
4. Calculate pH = - log[concentration of H3O]
5. The amt of sig figs is the # of decimal places in final answer

Question 12

Writing Half Reaction

Answer 12

e^- is symbol for electron
Ex)
Na(s) -> Na^+ (aq) + e^- (oxidation half reaction)
-electrons REMOVED
I2(s) + 2e^- -> 2I^- (aq) (reduction half reaction)
- electrons ADDED

Question 13

When looking at possible reactions

Answer 13

the metal that is placed higher in the activity series can replace (‘reduce’ was used in this specific case) the other

Question 14

Finding volume of base to titrate given mass of acid

Answer 14

1. Find moles of acid
2. Find mol of OH needed (1 mol OH for every H)
3. Divide mol of Oh by Molarity of base soln to get volume of base soln in Liters

Question 15

Finding molarity of base soln

Answer 15

1. find molar mass of acid
2. find moles of OH used for every mol of acid (1 OH for every H)
   3.Divide by moles of OH by liters of OH used

Question 16

Finding molar mass of monoprotic acid w/ base titrations

Answer 16

1. Find mol of base - multiply volume of base w/ Molarity
2. Multiply w/ ratio (mol of H / mol of base)
3. Divide mass of monoprotic acid w/ moles to get molar mass

Question 17

Solving limiting reactant problems in precipitating solutions

Answer 17

1. Write reaction.
2. Identify important species (AKA reactants that make up precipitate)
   *Note: precipitation reactions run to completion
   **HOWEVER If target reactant is NOT a reactant of precipitate, just find the moles of it straight from the given moles
3. Find the limiting reactant
4. After finding the limiting reactant, use the mole ratio to find how many moles of target reactant is left over.