3 fundamental types of batteries
-Primary Cells
non-rechargeable, non-reversible, 1 direction (alkaline batteries)
-Secondary Cells
rechargeable, reversible, 2 directions (car batteries)
-Fuel Cells
re-fillable - like a battery cell to which you can add more reactants (space)
In a galvanic cell...
oxidation and reduction take place at the same time, but at different electrodes
Both reduction and oxidation occur simultaneously, oxidation at the anode and reduction at the cathode.
also known as voltaic cells or batteries
What is the primary purpose of a salt bridge?
To balance the displacement of charge in the electrochemical cell.
Yes, we cannot accumulate a beaker of positive charges and beaker of negative charges. The chemistry simply won't operate unless there is a balance of charges. The salt bridge provides the
true or false? In a working electrochemical cell (+cell voltage), the electrons flow from the anode through the external circuit to the cathode.
true Yes. Remember for working electrochemical cells "FAT CAT" = "From Anode To CAThode
The purpose of an inert electrode is
to deliver/collect electrons
Yes. Inert electrodes don't take active role in the chemistry at hand, they are just a conduit for electrons.
Standard reduction potentials are established by comparison to the potential of which half reaction?
2H+ + 2e- ? H2
this is the half-reaction to we establish as the "ground zero" for measuring standard potentials. We can use the SHE (Standard Hydrogen Electrode) to measure other standard
potentials.
E standard = 0V
standard reduction potential
Look on the LEFT side of the half-reactions for substances that are going to be reduced (oxidizing agents). Look on the RIGHT side to find substances that are going to be oxidized (reducing agents).
voltaic/ galvanic cell
produces a positive voltage through a spontaneous redox reaction
batteries
E(standard)>0, delta G(standard)<0, k>1
electrons flow from anode to cathode
oxidation at the anode (-)
reduction at cathode (+)
electrolytic cell
nonspontaneous, needs power source to drive reaction forward
E(standard)<0, delta G(standard)>0, K<1 (reactant favored)
electrons flow from anode to cathode
oxidation at the anode (+)
reduction at cathode (-)
charge (Q)
Coulombs =
amp *sec
current (I)
Amps= 1 C/ 1s
___Q (charge)/ t (time)
voltage (v)
energy(J)/charge (C) = electrical potential
intensive property
*ability to pull e- from another metal
-no bonds
-no metal touching
key characteristics of batteries: potential (E)
potential is the voltage
**the larger the potential is, the more useful the battery is
can out more batteries to overcome low potential
-amount of work needed to move charge
key characteristics of batteries: capacity (Q)
the AMOUNT of reactant
it tells us how to much total charge a battery can generate
it is often referred to as total energy
- charge that is extracted from your reactants
(limiting reagent)
key characteristics of batteries: current (I)
how fast the battery can generate charge. VIP!!
-how much energy can be transferred and how quickly
key characteristics of batteries: power (P)
V(energy)*I
the higher the current, the higher the power
the higher the potential, the higher the power
key characteristics of batteries: Cycle life
how well the battery recharges
(I
t/n
F)
I - Amps
t- seconds
n - moles of e
F - 96,485
want batteries to be
1. light weight
2. small
3. solid phase
=energy density + power density
Dry cells
batteries without liquids. SLOW reactions with constant voltage and have low currents (D is max - different currents)
-alkaline battereis (n+k) (1.5 V - all same potential)
contain electrolytes in a paste
Lead storage battery
car battery, almost all solid except for liquid concentrated sulphuric acid
fuel cell
need to have fuel continuously added
shorthand notation
anode| anodic sol || cathodic sol | cathode
put commas if same phase, put inert electrode on side if no solids to conduct reaction
(reactant, product) charges go in middle because no charges on solids
work=?G=
?nFE
So the potential E
is not the standard potential but the potential now.
n is the number of electrons per mole reaction as the equation is written.
F ( faradays constant) converts between mole of electrons and charge in coulombs. Note: the energy you
?G?=
?RTlnK
E?=
E?=(RT/nF)*lnK
E?=(0.05916/n)*logK
K=
K=exp(nFE?/RT)
E=
E=E??(RT/nF)*lnQ
E??(0.0257/n)*lnQ
E=E??(0.05916/n)*logQ
Q= Reactant/Product (molar)
Which of the following batteries are rechargeable?
I. Alkaline Battery
II. NiMH Battery
III. Lithium Battery
IV. Lithium Ion Battery
V. Lead-Acid Battery
2,4,5
Primary batteries (like alkaline batteries or lithium batteries) are not rechargeable. Secondary batteries (like NiMH batteries, lithium ion batteries, and lead-acid batteries) are rechargeable. Remember lead-acid batteries are another name for car
Which of the following are important characteristic of the proton exchange membrane (PEM) in a PEM fuel cell?
It is permeable to protons.
It physically separates the half-reactions.
It must be stable in an acidic environment.
It is coated with catalysts that increase the rates of both the oxidation and reduction reactions.
not It must withstand the high operating
rules for assigning oxidation numbers
1. atoms in standard states are neutral
2. group 1 is +1
3. usually oxygen is -2 but can be -1, hydrogen can be +/-1
4. assign electronegative atoms first
in acidic conditions
1. assign oxidation numbers
2. split reactions into half reactions
3. must balance atoms
4. balance oxygen with H2O
5. balance H with H+
6. balance e-
7. add to get overall reaction
in basic conditions
1. .assign oxidation numbers
2. split reactions into half reactions
3. must balance atoms
4. balance oxygen with H2O
5. balance H with H+ and OH- (add OH- to both sides)
6. balance e-
7. add to get overall reaction
electrons lowest in energy for
the metal product because it will be the most stable
rules for aqueous and gaseous and solids
-anything with charge is aqueous
-Cl, Fl, and H are gaseous
-anything neutral is solid
You turn on a flashlight containing brand new NiCad batteries and keep it lit for a minute or two. Which of the following can be considered TRUE regarding the chemical state of these batteries?
I. ?G for the battery reaction is negative.
II. Ecell > 0
III
1 and 2
3. only when battery is dead
4. battery maintains constant cell potential entire life
Which of the following batteries are rechargeable?
I. Alkaline Battery
II. NiMH Battery
III. Lithium Battery
IV. Lithium Ion Battery
V. Lead-Acid Battery
2, 4, 5. secondary batteries are rechargeable. primary aren't.
lead- acid batteries - aka car batteries
What metal (in various oxidation states) is present at both the cathode and the anode in a typical car battery?
lead
lithium
cadmium
nickel
zinc
lead. car acid batteries are called lead acid
The net redox reaction in a fuel cell is given below:
2H2 + O2 ? H2O
What is the reaction at the anode in a fuel cell?
H2 ? 2H+ + 2e-
Which of the following is NOT an important characteristic of the proton exchange membrane (PEM) in a PEM fuel cell?
It is permeable to protons.
It physically separates the half-reactions.
It must be stable in an acidic environment.
It must withstand the h
The proton exchange membrane in a PEM fuel cell is coated with catalysts that increase the rates of both the oxidation and reduction half-reactions (which it physically separates) and is permeable to protons. As protons (H+) are another name for acid, the