Batteries Flashcards
What is an oxidation reaction?
loss of electrons (LEO-lose electrons: oxidation)
What is a reduction reaction?
gain of electrons (GER-gain electrons: reduction)
How do electrochemical cells work?
there are 2 batteries in an electrolyte solution, one battery gives electrons (anode) and the other takes electrons (cathode). There are electrons flowing from the anode to the cathode and a semi-permeable barrier is in between them.
What is an anode?
battery that gives electrons
What is a cathode?
battery that takes electrons
What is a redox half-reaction?
either the oxidation or reduction reaction component of a redox reaction
What are the steps to identifying a reduction half-reaction?
If as proceeding from reactants → products an element/molecule gained electron(s)
What are the steps to identifying an oxidation haf-reaction?
If as proceeding from reactants → products an element/molecule lost electron(s)
What are the steps to writing an overall redox reaction?
1) Electrons need to cancel out, electrons are never shown
2) Multiply each half-reaction by some number to get the same number of electrons on each side to cancel electrons
3) Combine the two half-reactions
What are the elements in a galvanic (voltaic) cell?
zinc atom and copper ion
Does zinc want to lose or gain electrons in a galvanic (voltaic) cell? How many does it lose/gain?
loses 2 electrons to become stable
Does copper lose or gain electrons in a galvanic (voltaic) cell?
gains 2 electrons
What helps achieve an electron current in a galvanic (voltaic) cell?
zinc and copper are connected through a copper cable
What kind of solution are zinc and copper put in for a galvanic (voltaic) cell?
an aqueous solution with sulfate
What kind of charge is accumulated in the zinc environment of a galvanic (voltaic) cell?
positive charges
What kind of charges are accumulated in a copper environment of a galvanic (voltaic) cell?
negative charges
What kind of bridge is added to the aqueous solution of a galvanic (voltaic) cell?
a salt bridge that has Na+ and Cl- with a cotton material at the end
Does Na+ or Cl- of the salt bridge go into the zinc solution of a galvanic (voltaic) cell?
Cl-
Does Na+ or Cl- go into the copper solution of a galvanic (voltaic) cell?
Na+
Does the metal get thicker or thinner on the zinc side of a galvanic (voltaic) cell?
thinner
Does the metal of the copper side get thinner/thicker in a galvanic (voltaic) cell?
thicker
What is an alkaline cell?
a type of battery that uses a chemical reaction between zinc and manganese dioxide, powered by an alkaline electrolyte like potassium hydroxide
What is the alkaline cell equation?
Zn + 2MnO2 + H2O –> Mn2O3 + 2OH(-) + Zn(2+)
What is oxidized in an alkaline cell?
zinc
Zn → Zn(2+) + 2e(-)
What is reduced in an alkaline cell?
2MnO2
e(-) + MnO2→ Mn(+3)2O2(-3)
What is oxidation number rule #1?
Oxidation number of an atom in a free element is 0
What is oxidation number rule #2?
Oxidation number of a monoatomic ion is equal to its charge
What does monoatomic mean?
single atom
What is oxidation number rule #3?
Sum of oxidation number of all atoms in:
a) Neutral molecule is 0
b) Polyatomic ion is a charge of an ion
What is oxidation number rule #4?
In compounds, metals have positive oxidation numbers
a) Alkali metals always have a +1
b) Alkali earth metals always have +2
What is oxidation number rule #5?
Nonmetals are assigned oxidation numbers in the order of:
Fluorine: -1
Hydrogen: +1
Oxygen: -2
Group 7A: -1
Group 6A: -2
Group 5A: -3
