Chem Chapter 16 and 19

Binary acids

Have acidic hydrogens attached to a nonmetal atom

Ex: HF, HCl, HBr

Bond polarity (electronegativity)

Acid strength increases as the polarity of the bonds increases (electronegativity increases)

Increases right and up on the periodic table

Bond strength

The more tightly the hydrogen is held (smaller atom), the weaker the acid

Bigger atomic size → stronger acid

Increases left and down on the periodic table

Conjugate base stability

The greater stability the stronger the acid

Stability increase right and down on periodic table

Oxyacids

Acidic hydrogen atom bonded to an oxygen atom which is bonded to a nonmetal

Electronegativity of Y

The more electronegative the Y atom:

The stronger the oxyacid and the weaker and more polarized the O-H bond

Use electronegativity when comparing oxyacids with…

Same number of Os

Number of O atoms

The more O atoms attached to Y, the stronger the oxyacid, H-O bond is more polarized and increases acidity

Oxidation state of Y

The larger the oxidation state of Y the stronger the oxyacid

A compound becomes more acidic as…

The positive charge increases

A compound becomes more basic as…

The negative charge increases

Polyprotic acids

Acids that contain 2 or more ionizable hydrogens

They ionize in successive steps, 1st ionization takes place to greater extent

Calculating pH of polyprotic acids

1st step is the only one that significantly contributes to H3O concentration/pH

Redox reactions

One element increase its oxidation state, another decreases its oxidation state

Both need to happen at the same time

Reduction

Gaining an electron, the oxidizing agent, oxidation state is reduced

Oxidation

Losing an electron, the reducing agent, oxidation state increases

Rules for assigning oxidation states

Elemental form →

Monoatomic ion → same as charge

Fluorine → -1

Oxygen → -2

Hydrogen → +1

Halogens → -1

The sum of the oxidation states…

Should be equal to the charge of the compound

Balancing redox reactions in neutral

Split reaction and balance atoms

Add in electrons as reactant for reduction half reaction and as product for oxidation half reactions

Balance, add, and cancel out

Balancing redox reactions in acidic solution

Split reaction and balance

Add H2O to balance O and add H+ to balance H

Add in electrons, balance, add, cancel out

Balancing reactions in basic solutions

Split reaction and balance

Balance elements other than H and O, then add H2O and H

Neutralize H+ by adding OH to both sides

Add in electrons, balance, add, cancel out

Electrochemical cell

Device where a chemical reaction either produces or is carried out by an electrical current

Voltaic/Galvanic cell

Cell that produces electrical current from a spontaneous chemical reaction

Electrons flow spontaneously and current can be used to do work

∆G < 0, K > 1

Electrolytic cell

Requires a power source to drive the reaction

Not spontaneous

∆G > 0, K < 1

Metal or graphite electrode

The flow of electrons requires a conductive solid electrode to allow transfer

Anode

Electrode where oxidation occurs and negative electrode of the cell

Loses mass during electrochemical reaction

Cathode

Electrode where reduction occurs and positive electrode of the cell

Gains mass during electrochemical reaction

Salt bridge

Inverted U shape tube that connects 2 half cell compartments

Contains a strong electrolyte

Upon oxidation…

Positive charges build up at anode and anions in the salt bridge will move towards the anode

Upon reduction

Negative charges will build up at the cathode and cations in the salt bridge will move toward the cathode

Line notation

Anode || Cathod

Electromotive force/ Cell potential or voltage

Force that pushes negatively charged electrons away from anode and towards cathode

Standard cell potential

Difference in potential energy of electrons in oxidation and reduction half reactions

Ecell= Ecathode - Eanion

Standard reduction potential

Can only be measured relative to another half reaction

Standard hydrogen electrode

2H + 2e- → H Ecell = 0V

Standard reduction potential (the higher the Ered)

The species on the left:

Has a stronger ability gain e-

Is easier to be reduced

Is a stronger oxidizing agent

Is a better cathode material

Is on the ride side of cell notation

Standard reduction potential (the lower the Ered)

The species on the right:

Is easier to be oxidized

Is a stronger reducing agent

Is a better anode material

Is on the left side of cell notation