Electrochemistry

Question 1

Oxidation:

Answer 1

The complete or partial loss of electrons or gain of oxygen. Ionic compounds.

Question 2

Reduction:

Answer 2

The complete or partial gain of electrons or loss of oxygen. Covalent compounds.

Question 3

OIL RIG:

Answer 3

Oxidation is Losing electrons reduction is gaining electrons.

Question 4

Reducing Agent:

Answer 4

The substance that donates electrons.

Question 5

Oxidizing Agent:

Answer 5

The substance that accepts electrons.

Question 6

What is the oxidation number of any pure element?

Answer 6

0.

Question 7

What is the oxidation number of a monoatomic ion?

Answer 7

It’s charge.

Question 8

What is the oxidation number for alkali metals in compounds?

Answer 8

+1

Question 9

What is the oxidation number for alkaline earth metals in compounds?

Answer 9

+2

Question 10

What is the oxidation number for halogens?

Answer 10

-1

Question 11

What is the oxidation number of H in most compounds? What is its exception?

Answer 11

+1. Except for ionic hydrides such as NaH where H = -1.

Question 12

What is the oxidation number of O in most compounds? What is it’s exception?

Answer 12

-2. Except in peroxides such as H2O2 where O = -1

Question 13

What is the sum of the oxidation numbers in a compound?

Answer 13

Zero if neutral, equal to the charge if an ion.

Question 14

When a substance increases in oxidation number from reactants to products, it is ________ (__).

Answer 14

oxidized, RA

Question 15

When a substance reduces in oxidation number from reactants to products, it is ________ (__).

Answer 15

reduced, OA

Question 16

How can you tell if a reaction is spontaneous?

Answer 16

The OA must be above the RA on the page 7 table.

Question 17

How do you predict redox reactions?

Answer 17

1. Identify the types of atoms and ions in a mixture.
2. Label each species as either an OA or RA. Combine ions if required.
3. The reaction will occur between the strongest OA and RA. Identify them.
4. Write down each of their half-reactions.
5. Even up the electrons by multiplying by the LCD.
6. Write spont/non-spont over the arrow.

Question 18

How do you calculate sample [ ] in a titration?

Answer 18

1. Calculate the moles of titrant uses (n = c*v)
2. Calculate moles of the sample (mole/ratio)
3. Calculate [ ] of the sample (c = n/v)
   Acidify the sample, never the titrant. The H+(aq) in the sample makes the OA titrants strong only in the presence of the sample.

Question 19

How do you balance redox reactions in an aqueous acidic environment?

Answer 19

1. Use oxidation numbers to find the redox and oxidation half-reactions
2. Balance all elements except H and O
3. Balance O’s by adding H2O(l)
4. Balance H’s with H+(aq)
5. Balance the charge by adding electrons
6. Make the electrons in both half-reactions the same by multiplying by the LCD
7. Check over that mass and charge balance and create a net equation.

Question 20

How do you identify the number of electrons transferred in a redox reaction?

Answer 20

1. Use oxidation numbers to determine the RA and the OA
2. Take subscripts into account to find the electrons needed
3. Use coefficients to determine the electrons transferred total.

Question 21

Disproportionation:

Answer 21

When a single species is both oxidized and reduced. This only occurs when the element changes charge in 2 places in the products.