Electrochemistry Flashcards
Oxidation:
The complete or partial loss of electrons or gain of oxygen. Ionic compounds.
Reduction:
The complete or partial gain of electrons or loss of oxygen. Covalent compounds.
OIL RIG:
Oxidation is Losing electrons reduction is gaining electrons.
Reducing Agent:
The substance that donates electrons.
Oxidizing Agent:
The substance that accepts electrons.
What is the oxidation number of any pure element?
0.
What is the oxidation number of a monoatomic ion?
It’s charge.
What is the oxidation number for alkali metals in compounds?
+1
What is the oxidation number for alkaline earth metals in compounds?
+2
What is the oxidation number for halogens?
-1
What is the oxidation number of H in most compounds? What is its exception?
+1. Except for ionic hydrides such as NaH where H = -1.
What is the oxidation number of O in most compounds? What is it’s exception?
-2. Except in peroxides such as H2O2 where O = -1
What is the sum of the oxidation numbers in a compound?
Zero if neutral, equal to the charge if an ion.
When a substance increases in oxidation number from reactants to products, it is ________ (__).
oxidized, RA
When a substance reduces in oxidation number from reactants to products, it is ________ (__).
reduced, OA
How can you tell if a reaction is spontaneous?
The OA must be above the RA on the page 7 table.
How do you predict redox reactions?
- Identify the types of atoms and ions in a mixture.
- Label each species as either an OA or RA. Combine ions if required.
- The reaction will occur between the strongest OA and RA. Identify them.
- Write down each of their half-reactions.
- Even up the electrons by multiplying by the LCD.
- Write spont/non-spont over the arrow.
How do you calculate sample [ ] in a titration?
- Calculate the moles of titrant uses (n = c*v)
- Calculate moles of the sample (mole/ratio)
- 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.
How do you balance redox reactions in an aqueous acidic environment?
- Use oxidation numbers to find the redox and oxidation half-reactions
- Balance all elements except H and O
- Balance O’s by adding H2O(l)
- Balance H’s with H+(aq)
- Balance the charge by adding electrons
- Make the electrons in both half-reactions the same by multiplying by the LCD
- Check over that mass and charge balance and create a net equation.
How do you identify the number of electrons transferred in a redox reaction?
- Use oxidation numbers to determine the RA and the OA
- Take subscripts into account to find the electrons needed
- Use coefficients to determine the electrons transferred total.
Disproportionation:
When a single species is both oxidized and reduced. This only occurs when the element changes charge in 2 places in the products.
