exam 2 chem prep

Exothermic process

Releases heat

• negative number = H is less than 0

Conversion for MHz

10^6Hz

Delta E

heat + work

Q “how much heat is required…”

Mcat!

What type of orbitals does n=1 have

S

What type of orbitals does n=2 have

S and p

What type of orbitals does n=3 have

S,p and d

What type of orbitals does n=4 have

S,p,d and f

How do find the net ionic reaction

After you write the complete ionic equation you cross out the elements that are both the reactants and product side

Strong acids:

HCl, HBr, HI, HNO3, HSO4, HClO3, and HClO4

• the rest of acids are weak

How to write complete ionic equations

• write after balancing

• Write out each element individually with correct coefficients

• Don’t separate solids and strong acids

• Ex: Ba(OH)2 = Ba ^+2 + 2OH

• Ex: Na(ClO) = Na^+ + ClO^-

If a cation-anion pair is soluable its

Aqueous (aq)

If a cation-anion pair is insoluable its

Solid (s)

All group 1 and ammonium salts are…

Soluble

• this rule holds above others

All nitrates and acetates are…

soluable

Phosphates and carbonates are…

Insoluable

Sulfides(S) and hydroxides (OH-) are…

Insoluable

• UNLESS paired with Ba2+

Most sulfates (SO) are…

Soluable

• UNLESS paired with Ba2+ or Pb2+

Halides (Cl-, Br-, I-) are…

Soluable

• UNLESS paired with Ag+ and Pb2+

Units of enthalpy

J or kJ

lower atomic mass of a substance means…

Bigger effusion

Bigger atomic mass means…

A lower rate of effusion

Effusion

The process where gas molecules escape from a container through a tiny hole or opening to a vacuum or lower pressure area

How to calculate workforce

Hc/landa max

H: Planck constant: 6.626 × 10^ -34 Js

C: speed of light: 2.998×10^ 8 m/s

Landa max: given in nanometers (nm = 10^-9 m)

• plug in values

How to solve: when given reactions and their enthalpys along and are given a goal reaction and told to find its enthalpy you…

• Use the elements that are in the goal reaction, you find them in the given reactions, and you multiply or divide by the change that needs to be done to the reaction

• If the element is in the reactant side but needs to switch to the product side or vice versa you reverse the sign of the enthalpy

• after all your changes are made to your enthalpies your sum of all all the enthalpies is the enthalpy for the goal reaction

How to solve: the visible emission spectrum of hydrogen involves lines ending in n finally = 2. What is n initial for the line at 434nm.

Equation: 1/landa = (Rh rydbergs constant (1.097×10^7m^-1)) (1/nf² - 1/ni²)

• Landa is given in nm (make sure its written in scientific notation

• solve for ni

• First isolate the n’s then isolate ni

• Convert fraction of nf to decimal to make it easier

When asked about quantum numbers and it says emission that means the value of n is

Decreasing

When asked about quantum numbers and it says absorption then the value of n is

Increasing

How to solve: the longest wavelength light able to cause the release of a photoelectron from sodium metal is 452nm.

What is the work function of sodium in J

Calculation for workforce:

= hc/landa max

• Landa max is the number provided in nm but convert to m (n=10^-9)

Moving decimal place to the left for scientific notation

You add the places moved to the exponent of 10

• and vice versa

When you multiply in scientific notation you do what to the exponents

Add

When you divide in scientific notation you do what to the exponents

Subtract

How to solve: the visible emission spectrum of hydrogen involves lines ending in nf=2. What is ni for the line at 434nm

• equation: 1/landa = rydbergs constant ( 1/ n final ² - 1/n initial ²)

• Convert 434nm and convert to scientific notation

• N= 10^-9

• add exponents

Moving decimal to the right makes the exponent

Negative

• 0.005 = 5 × 10^-3

Moving decimal to the left makes the exponent

Positive

• 5,000 = 5×10³

Rules for quantum numbers to be permissible (n)

• must be a positive number (1,2,3,4, etc)

• 0,-1,1.4 make it NOT permissible

Rules for quantum numbers to be permissible (l)

• must be a integer ranging from 0 or n-1

• If n=2 then this can only be 0 or 1

Rules for quantum numbers to be permissible (m)

• Must be an integer ranging from positive or negative l or 0

• |m| can NOT be greater than l

Longest wavelength corresponds with

Smallest energy difference between the two energy levels

• after you do the whole 1/nsmall - 1/nbig

Endothermic process

Gains heat

• positive # = H is greater than 0

State function

It depends only on the current state (ex: pressure, temp, V) so its not path dependent (how it got there)

• Ex: H (its fixed)

H

Type of energy that tracks how much heat is absorbed or released

• enthalpy

N=1

Refers to ground state

According to the Heisenberg uncertainty principle it is impossible to know precisely both the position and ____ of an electron

Momentum (because measuring one affects the other)

• neither can be known at the same time

Speed of light ( c ) =

(Frequency)(Landa)

All of the orbitals in a given electron shell have the same value as the ____ quantum numbers

Principal

All of the orbitals in a given subshelll have the same value as the ____ quantum number

Principal

• determines where on the orbital the shell is

Rules for n (principle quantum #)

• positive integer

Rules for l (angular momentum quantum #)

Integer from 0 to n-1

Rules for ml (magnetic quantum #)

Any value from positive to negative l

Rules for ms (spin quantum #)

Up = +1/2, down= -1/2

In one electron systems the energy only depends on…

N

Negative enthalpy means

A exothermic reaction and heat is released

Positive enthalpy means…

Endothermic reaction and heat is absorbed

True statements about enthalpy

• It’s dependent on the state of the reactants, products, and how much matter is present

• It is NOT an intensive property

• The ___ change for a reaction is equal in magnitude, but the opposite in sign, to the enthalpy change for the reverse reaction

When a system ____, delta E is always negative

Gives off heat and does work

• ex: the delta E of a system that releases 12.4J of heat and does 4.2J of work on the surroundings is ____J