Stoichiometry and Gases

By: Carson Ram & Thomas Schweinfurth

The Periodic Table

Atomic Number:Representative of the protons

Atomic Symbol:Letter representation of the element

Atomic Weight:Representative the neutrons & protons

The Periodic Table

Period:Across a row

Family:Down acolumn

Metals

Metalloids

Nonmetals http://wps.prenhall.com/wps/media/objects/5524/5656731/ebook/blb11_flash_main.html?chapter=null&page=null&anchory=null&pstart=null&pend=nuall

1A: Alkaline2A: Alkaline Earth Metals

Chalcogens

Halogens

8A: Noble Gases

Atoms, Molecules, and Ions

• Molecular Formulas: Indicate the actual numbers and types of atoms in a molecule

• Empirical Formulas: Give only the relative number of atoms of each type in a molecule

• Example…

Molecular Formula C2H4

Empirical Formula CH2

Chemical Nomenclature

• Tips & Tricks for naming cations:– Cations formed from metal atoms have the same name

as the metal:• Ex. Ca+2

calcium ion

– If a metal can form different ions, the positive charge is indicated by a Roman numeral in parenthesis behind the name of the metal:• Ex. Fe2+ iron (II) ion Fe3+ iron (III) ion

– Cations formed from nonmetal atoms have names that end in –ium:• NH4

+ammon-ium ionH3O+ hydron-ium ion

Chemical Nomenclature

• Tips & Tricks for naming anions: (Part One)– The names of monatomic anions are formed by

replacing the ending of the name of the element with –ide:• Ex. Br- Brom-ide Ion Cl-Chlor-ide Ion

– Polyatomic anions containing oxygen have names ending in –ate or –ite.• Ex. NO3

- Nitr-ate Ion NO2- Nitr-ite Ion

– The Prefix per- indicates one more atom than the ion ending in –ate.

– The Prefix hypo- indicates one fewer atom than the ion ending in –ites.

Chemical Nomenclature

• Tips & Tricks for naming anions: (Part Two)– Anions derived by adding H+ to any oxyanion are

named by adding as a prefix the word hydrogen or dihydrogen, as appropriate.• Ex.• PO4

3- phosphate

• HPO42- hydrogen phosphate

• H2PO4- dihydrogen phosphate

– Names of ionic compounds consist of the cation name followed by the anion name• Ex. NaCl Sodium Chloride

Structuring

Q : The Charge

Z : Atomic Number

A : Mass Number

Percentage Compostitions

Formula Weight: Sum of the atomic weights of each atom in its chemical formula.

Example:Calculate the percentage of carbon in C12H22O11.

Addition of Atomic Weights:12 C atoms = 12 (12.0 amu) = 144.0 amu22 H atoms = 22 (1.0 amu) = 22.0 amu11 O atoms = 11 (16.0 amu) = 176.0 amu

342.0 amu

Atomic Weight of Carbon:12.0 amu

Avogadro’s Number

• Named after Amedeo Avogadro (1776-1856)

• NA = 6.02 x 1023 atoms / 1 mol

• 1 mol ‘Element’ = 6.02 x 1023 atoms• 1 mol ‘Compound’ = 6.02 x 1023 molecules• 1 mol ‘Ions’ = 6.02 x 1023 ions

Limiting Reactants

• Limiting Reagent: Determines, or limits, the amount of product formed.

• Left over reactants are often called excess reactants.

• Theoretical Yield: Quantity of product calculated to form

• Actual Yield: Quantity of product actually obtained

Gases

• Standard temperature and pressure (STP) is 273.15 K and 1 atm.– 1 atm = 760 mm Hg = 760 torr = 101.325 kPa

• Boyle’s Law: States that the volume of a fixed quantity of gas maintained at constant temperature is inversely proportional to the pressure. – PV = constant

• Charles’s Law: States that the volume of a fixed quantity of gas maintained at a constant pressure is directly proportional to the absolute temperature.– V / T = constant

Gases

• Avogadro’s Hypothesis: Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.

• Avogadro’s Law: states that the volume of a gas maintained at constant temperature and pressure is directly proportional to the number of moles in the gas.– V / n = constant

Ideal Gas Law

• The ideal-gas equation is… PV = nRT.• R is the gas constant. – R=8.314 J/molK R=0.08206 Latm/molK

• Remember! Temperature is in Kelvins, not degrees Celsius.

More About Gases

• If n and T are constant, the values of P and V can change, but the product of PV must remain constant, so:– P1V1=P2V2

• When just n is constant, P,V, and T can all change but the product of (PV)/T must remain constant so:– (P1V1)/T1=(P2V2)/T2 Often called the combined

gas law

Partial Pressure

• The total pressure of a mixture of gases equals the sum of the pressures that each would exert if it were present alone:– Pt = P1+P2+P3

• Each gas in a mixture behaves independently so we can relate the amount of a given gas in a mixture to its partial pressure:– P1 / Pt = (n1RT/V) / (ntRT/V) = n1/nt mole fraction

– P1=(n1/nt )Pt

Graham’s Law and rms Speed

• Particles with lighter masses have a higher rms speed.– u= M is molar mass

• Graham’s law states that if we have two gases at the same temperature and pressure in containers with identical pinholes, and r is the rate of diffusion, then:– r1/r2=

M

RT3

)2(

1)(

M

M

Van der Waals

• Van der Waals recognized that the ideal gas equation could be corrected to account for the effects of attractive forces between gas molecules and for molecular volumes.

• Constant a is a measure of how strongly the gas molecules attract each other and constant b is a measure of the small but finite volume occupied by the gas molecules themselves.

• (P+(n2a)/V2)(V-nb)=nRT

Thanks to…

Chemistry: The Central Science by T. Brown, H. LeMay, B. Bursten, and C. Murphy