Electrochemistry Flashcards
What is Electrochemistry?
The study of the interconversion of chemical energy and electrical energy.
What does it mean for an atom to be in a ground state?
All of its electrons are in the lowest available energy levels.
What does it mean for an atom to be in an excited state?
Electron absorbs energy and jumps to a level of higher energy.
In what form do electrons release release energy?
electromagnetic radiation (light)
What is Oxidation?
The loss of electrons.
When an electron is removed from a neutral atom it becomes what?
A cation
What is a cation?
A positively charged atom with a decrease in its oxidation state. (lost electrons)
What is reduction?
The gain of electrons.
When an electron is added to a neutral atom it becomes what?
An Anion
What is an Anion?
an atom that is negatively charged and has a decrease in its oxidation state. (gained electrons)
What is an electrolytic cell?
When energy is used to force a non-spontaneous chemical reaction to occur.
What is a battery?
A collection of electrochemical cells (voltaic cells) in which a chemical reaction occurs spontaneously to produce electric energy.
Where does oxidation occur?
In the anode (the positive electrode)
Where does reduction occur?
the cathode (the negative electrode)
What is a half-reaction?
The reaction occurring at each electrode.
What are energy levels?
Regions in the electron cloud where electrons are likely to be found.
Where is the lowest energy level?
Closest to the nucleus
Where is the highest energy level?
Farthest away from the nucleus
What do electrons occupy first?
The lowest available energy level.
What are valence electrons?
The outermost electrons in an atom.
What does the period (row) correspond to?
The highest energy level occupied by the valence electrons in an element (row=ring)
What does the group (column) correspond to?
The number of valence electrons in an element.
What is an ion?
An atom that has a charge because it has gained or lost electrons.
What is the amount of charge equal to?
The number of electrons lost or gained.
What happens to elements in groups 1,2,13?
They lose electrons (oxidation) and form cations.
What happens to elements in groups 15,16,17?
They will gain electrons (reduction) and form anions.
What are ionic compounds?
Compounds formed by the attraction between positive and negative ions. The charge must be balanced, resulting in a charge with no net charge. (typically metal and non-metal)
Phase changes that require heat are what?
endothermic
Phase changes that give off heat are what?
exothermic
What is the molar mass of the compound?
The sum of the molar masses of the individual elements that make up the compound.
How do you determine the percent by mass of an element in a compound?
% by mass of element = total mass of element in compound divided by total mass of the compound multiplied by 100.
What is a chemical equation?
A record of what happens in a chemical reaction. It shows formulas of all the reactants on the left side of the arrow and the formulas of all the products on the right hand side.
What is a balance chemical equation?
It has the same number of atoms of each element on either side of the arrow. When balanced the coefficients show the number of moles (mole ratio) of each substance required for a complete reaction.
What is solubility?
The amount of solute that will dissolve in 100g of solvent.
What is dissolving?
A physical change that involves heat. (dissolving and dissociation can be represented by an equation)
If a solution gets colder when a solute dissolves then what change occurs?
endothermic change
If a solution gets warmer when a solute dissolves then what change occurs?
exothermic change.
Where are the protons and neutrons?
Clumped together in a very small dense nucleus.
Where are electrons inside of an atom?
Electrons are found outside of the nucleus in various electron clouds.
What are principle energy levels(n)?
specific distances from the nucleus (rings)
What is the Bohr model?
An atom model that shows the principle energy levels as rings around the nucleus.
How many electrons fit in the first energy level?
2
How many electrons fit in the second energy level?
8
How many electrons fit in the third energy level?
18
How many electrons fit in the fourth energy level?
32
Why are valence electrons very important?
They are the electrons that are involved in chemical reactions and determine the element’s chemical properties.
What happens when elements undergo chemical reactions? (in terms of electrons)
They either share or exchange electrons with other elements.
What are the common oxidation states (ion charges) for elements?
What is the most stable electron configuration?
Completely filled energy level (8 valence electrons in the valence shell also known as octet rule)
Who made the Bhor Model?
Neil Bohr
Changes in electrons create new…
ions
Changes in protons create new…
elements
Changes in Neutrons create new…
isotope
What is Enthalpy (H)?
Tells us the heat of a system
What is temperature?
Measure of kinetic energy
How is enthalpy different from temperature?
Enthalpy is the transfer of energy of the system and temperature is measure of kinetic energy.
What is sodium chloride?
an ionic compound (made of ions)
What is Sugar?
A molecule (no ions)
What is dilute?
Less solute
What is the molar heat of a solution? ∆ Hsoln
The enthalpy change caused by the dissolving of 1 mole of a substance
What are solutions usually made up of’?
Ionic compounds and polar covalent compounds.
