chem 1770

19 left shoes + 14 right shoes. Which is the limiting reagent?

Right shoes are the limiting reagent. Products are 14 pairs of shoes and 5 excess left shoes.

10 H2 + 7 O2. Which is limiting, and what are the products?

10 H2O + 2 O2. H2 is the limiting reagent.

19 left shoes + 14 right shoes. Which is the limiting reagent?

Right shoes are the limiting reagent. Products are 14 pairs of shoes and 5 excess left shoes.

10 H2 + 7 O2. Which is limiting, and what are the products?

10 H2O + 2 O2. H2 is the limiting reagent.

Theoretical Yield

the maximum amount of product you could get from the amount of reagents you put in.

% Yield

(What you actually got) / (Theoretical Yield)

Solution

homogenous fluid mixture (ex. air)

fluid

liquids and gases

solvent

predominant material

solute(s)

minor component(s) - [minor in composition only]

Why is water an exceptional solvent?

Very polar, high ratio of heavy molecules, very small molecule

Insoluble

no appreciable dissolution (ex. sand in water)

Soluble

May dissolve to some reasonable degree to some limit (ex. salt or sugar in water - will come to some limit)

Miscible

Infinitely soluble with one another (ex. ethanol and H2O liquid, O2 and N2 gas)

Solubility Limit

point at which no more dissolving can occur

Solubility is temperature dependent

will be generally more soluble at higher temps

ppm, molarity, g/L are examples of what?

Measuring concentration

Molarity equation

M = mol/L (Liters measures the OVERALL SOLUTION!)

Concentration of 1 mol of NaCl in .5L H2O?

2 M

How does water conduct electricity?

Distilled water does not. Water with ions in it conducts electricity.

Electrolytes (operational definition)

will dissolve in water to allow electrical current

HCl dissolved in water forms what?

H+ and Cl- (ions are dissociated/solvated)

Strong electrolyte

completely dissociates (ex. NaCl --> Na+ and Cl-)

Weak electrolyte

doesn't completely dissociate (ex. CH3COOH

Examples of strong electrolytes

salts, acids (completely dissociate)

Examples of weak electrolytes

molecular compounds (NOT ionic)

Solubility of Cl-, Br-, I-

soluble with most cations, NOT with Ag+, Hg 2+, or Pb 2+

Solubility of NO3-

soluble with almost any cation

Solubility of CH3COO-

soluble with almost any cation (but not as well as NO3-)

Solubility of S2-

mostly insoluble

Solubility of OH- (and PO4 3- and CO3 2-)

mostly soluble. Very much so with M+ (Li, Na, K….), not so much with Ca, Mg….

Precipitation reaction

something precipitates out (a solid is formed)

Metathesis reaction

exchange reaction (ex. AB + CD --> AD + CB) [also called ion exchange]

2 salts meet - a precipitate is formed

Spectator Ions

don't do anything in the reaction after they are dissolved (stay dissolved throughout the reaction)

Brønsted acid

proton donor (electrolyte where cation is H+) Examples: HCl, CH3COOH….

pH (formula)

pH = -log [H+]

pH (scale and explanations)

0 --- acids --- [7 is neutral] --- bases --- 14 Adding acid, pH goes down (opposite true too)

If pH is 7, then what is the [H+]?

10 ^ (-7) M

Monoprotic acids

single proton acids (one H+)

Examples of Strong acids

HCl, HBr, HI, HClO4, HNO3, H2SO4 (first dissociation)

Examples of weak acids

Water, acetic acid, H2SO4 (second dissociation), all organic acids

How is H2SO4 both a strong and weak acid?

Has 2 dissociations (first is strong, second is weak) H2SO4 --> H+ and HSO4-

If an acid is defined by donating a proton, then what is a base?

Either accepts an H+ or donates and OH-

How is water both a weak acid and a weak base?

forms both an H+ and OH- when dissociated. H2O

How does a base make more OH- if it itself does not contain an OH-?

The base sucks up an H+ from a water molecule, forming an OH- in the process from the same water molecule

Is ammonia an acid or base?

BASE NH3 + H2O

The conjugate base of a strong acid must be…

a weak base (can't reform the original acid)

The conjugate acid of a strong base must be…

a weak acid

H3O+ is a strong acid, so H2O must be…

a weak base

OH- is a strong base, so H2O must be…

a weak acid

Neutralization reaction

"cancel out" the H+ or OH- (bring pH closer to 7)

What type of compound doesn't form electrolytes?

Organics

Reduction

"reduce" the charge (more negative or less positive) (accepts e-)

Oxidation

Loss of e-, more positive charge or less negative charge (usually associated with adding oxygen)

Oxidation or Reduction? Fe --> Fe2O3

oxidation

Oxidation or Reduction? Fe3+ --> Fe2+

reduction

Oxidation or Reduction? CH4 --> CO2

oxidation

Oxidation or Reduction? Any combustion reaction (speaking only of the carbon atoms)

Oxidation

Oxidation or Reduction? Cl2 --> 2Cl-

Reduction

If something is oxidized….

something else has to be reduced (things aren't oxidized for no reason)

Oxidation number of column 1

1+

Oxidation number of column 17

1-

Oxidation number of column 16

2-

Oxidation number of hydrogen (both)

1- with metals 1+ with nonmetals

What are the oxidation numbers of Fe and O in the compound Fe2O3?

Fe = Fe3+ = 3+ O.N. O = O2- = 2- O.N.

solid --> liquid

melting

liquid --> solid

freezing/fusion

gas --> liquid

condensation

liquid --> gas

evaporation

solid --> gas

sublimation

Vapor pressure

small pressure that exists with all liquids, some of the liquid becomes a gas

What is the solvent of air?

N2

O2 (g) and N2 (g) are ____ in solution.

miscible

What does humidity measure?

% of H2O in the air compared to what the air could hold

Salinity

measure of salt (usually NaCl) in units of g/L

Hyponatremia

too little sodium in your blood

reverse osmosis

using pressure and a semipermeable membrane to purify water

ΔH = …

H(final) - H(initial); Is a state function

At constant pressure, ΔH =…

q

When is "q" a state function?

at constant pressure

for liquid reactions, ΔH = …

ΔE (ΔV is so small, it can usually just be called 0)

ΔH = … (for gas reactions at constant P)

q (work and PV work cancel out, they are opposite signs)

Standard conditions

25 degrees C and 1 atm

ΔH (degree sign)

ΔH at standard temp and pressure

ΔH =…

H (products) - H (reactants)

ΔH is based on how much of a substance?

1 mole * their coefficient (in balanced rxn)

ΔT = …

q / c q=heat, C= heat capacity

C(sub s) = …

q / (mΔT) C(sub s) = specific heat

C(sub m) = …

q / (molΔT) C(sub m) = molar heat capacity

heat capacity of water

1 cal/(gK) or 4.184 J/(gK)

Energy flows from….

hot substance to cooler substance

Group 1 on PT

Alkali metals

Group 2 on PT

Alkaline earth metals

Groups 3-12 on PT

Transition metals

Group 16

Chalcogens

Group 17

Halogens

Group 18

Noble Gases

of protons in an atom corresponds to…

atomic number

of neutrons can be determined by…

subtracting atomic number from atomic mass

of electrons can be determined by…

(atomic number) - (charge)

isotope

atom with abnormal number of neutrons