Genchem Rutgers Exam 1(Chapter E to 4.8)

Types of units

English/Imperial, metric, SI

SI units

Prefixes used in

SI system

Temperature

K=°C +273

SI derived Unit

a unit derived by combining SI base units that shows up often

1 dm^3=

1 cm^3=

1 L

1 mL

Density

- mass/volume

- physical and intensive property

- can be used to identify pure substances

- can be used as a conversion factor

particles

atoms, ions, molecules

Energy

the capacity to do work

E = force distance = kgm^2*s^-2

Work (W)

change in energy thatresults when a Force (F) is exerted over a distance (d)

W= F×d

Kinetic Energy (Ek)

energy due to motion

Potential Energy (V)

energy due to position in a force field

Radiant Energy (E photon)

energy due to radiation

E total

Ek + V + Ephoton

According to the law of conservation of energy E Total is

0

What is energy measured in?

Joules (J)

15=1 kg×m^2×s^-2

calories (cal)

1 cal=4.184J

kilowatt-hour(kWh)

1 kWh=3.60×10^6 J

electron Volts (eV)

1 eV= 1.6022×10^-19 J

What is force measured in?

Newtons [N]

1N= 1 kg×m×s^-2

Force formula

F= m×a

Pressure formula

p= F/I^2

Accuracy

how close a measurement is to the true value

Precision

a measure of how close a series of measurements are to one another

Exact numbers

have an infinite number of significant figures

Inexact Numbers

those whose values have some uncertainty

sig figs in multiplication and division

least number of sig figs

sig figs in addition and subtraction

least number of decimal places

Dimensional Analysis

a mathematical technique that allows you to use units to solve problems involving measurements

Chemistry definition

the study of matter, the changes it undergoes, and the energy associated with these changes

matter

Anything that has mass and takes up space

atoms

smallest unit of matter

Physical State

- solid, liquid, or gas

- based on the strength of interactions that occur between particles making up the substance at a given temperature

- stronger interaction = less space and vice versa

composition

pure substance or mixture

pure Substance

A form of matter that has definite (constant) composition and distinct properties

- includes elements (one type of atom) and compounds (more than I type of atom)

mixture

A combination of two or more substances that are not chemically combined

Allotropes

Different forms of the same element

Isomer

Compounds with the same formula but different structures.

Mixture types

homogenous (mixture has components that are uniform throughout & are also called solutions)

heterogenous (mixture is not

uniform throughout, as the

components are discernible by

the naked eye)

Quantitative

measured and expressed with a number

Qualitative

Do not require measurement and are usually based on Observation

Extensive

Depends on the amount of matter

Ex: mass, volume

Intensive

Does not depend on the amount of matter

Ex: temperature and density

Physical Property

can be observed and measured without changing the identity of the substance

Chemical Property

Cannot be observed without converting a substance into another substance

Law at Conservation of Mass

- Matter is not created nor destroyed in any chemical or physical change

- 1789, Antoine Lavoisier

Law of Definite Proportions

All samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements

- 1797, Joseph Proust

- Ex: water's O to H ratio is 8:1, so all samples of pure H2O must have O:H mass samples be 8:1

- elements in compounds should be in fixed and discrete amounts

Law of Multiple Proportions

when 2 elements form a different compounds, the masses of element B that combine with 1g of element A can be expressed as a ratio of small WHOLE numbers

- 1804, John Dalton

- Ex: carbon monoxide and carbon dioxide both are made up of only carbon and oxygen, but their C:O ratios differ from each other

velocity

distance/time

conversion factor

- ratio

- units on the top of the fraction are different from the units on the bottom of the fraction

- the top of the fraction is "equal" to the bottom

- created from an equality statement

John Dalton's Atomic Theory(1808)

1. Each element is composed of tiny, indestructible particles called atoms

2. All atoms of a given element have the same mass and other properties that distinguish them from atoms of other elements

3. Atoms combine in simple, whole-number ratios to form compounds

4. Atoms of one element can't change into atoms of another element. In a chemical reaction, atoms only change the way that they are bound together with other atoms

J.J. Thompson's Cathode Ray Experiment

- cathode rays are composed of negatively charged particles that travel in straight lines

- atoms are divisible and the electron was discovered

Robert Millikan's Oil Drop Experiment

- charges on oil drops are whole-number multiples of the charge of a single electron

- the charge of an electron was determined

- the charge of a single electron was calculated to be -1.60 * 10^19 Coulomb (C)

Ernest Rutherford's gold foil experiment

the discovery of the nucleus and the disproving of the plum-pudding model of an atom

Thompson's Plum Pudding Model

electrons held within a positive nucleus/charged sphere

Rutherford's Nuclear Theory of an Atom

- most of the atom's mass and all of its positive charge are contained in a small core called the nucleus

- most of the volume of the atom is empty space dispersed with tiny, negatively charged electrons

- there are positively charged particles called protons in the nucleus. The number of protons in the nucleus must equal the number of electrons so that the atom is electrically neutral

James Chadwick

the nucleus also contains uncharged particles called neutrons. The mass of a neutron is similar to the mass of a proton

atomic mass unit(amu or u)

- unit of mass well suited for dealing with individual protons, neutrons, atoms, molecules, etc.

- avg atomic mass: f = natural abundance and m=mass;

- Average Mass(element) = fi(mi) + fi(mi)

Z(atomic number)

identity of an element determined by the number of protons

Atoms of an element must have the ______ amount of protons and ___________ amount of neutrons

same, different

ions

- they are not the same as atoms

- formed by a loss or gain of electrons to make cations(positive) and anions(negative)

isotopes

Atoms of the same element that have different numbers of neutrons, therefore having slightly different masses for each of the isotopes

mass number(A)

number of protons + number of neutrons

natural abundance

relative amount of an isotope in a naturally occurring sample of an element that is usually given in percentages

Mole(mol)

- unit of amount

- 1 mol = 6.022 * 10^23 entities

- that number above is Avogadro's number (NA)

Molar Mass (M)

- mass substance(g)/amount substance(mol)

- g/mol

- numerically equal to the atomic mass of the substance, but atomic mass units are amu/atom and molar mass is g/mol so don't mess it up

wave-particle duality of light

Sometimes light appears to behave like a wave, at other times like a particle depending on the specific scenario

wave nature of light

- the two-slit interference pattern can only be explained by a wave picture of light

Important characteristics:

- wavelength

- frequency

- amplitude

- energy

- speed

Wavelength

The distance between two corresponding parts of a wave

- measured in length units: nm, m, micrometers, mm

Frequency

the number of complete wave cycles that pass a point in a given time

- measure in cycles/s, s^-1, or Hz

- inversely proportional to wavelength

amplitude

the height of a wave's crest

- determines light intensity

Energy of a wave particle

- proportional to its amplitude and frequency

- greater energy means greater frequency and smaller wavelength

- lower energy means lower frequency and bigger wavelength

speed of light(c)

c=λ*v, c=3.00E8

- measured in m/s

order of Electromagnetic radiation energy

(least to greatest) radio waves, microwave, infrared, visible light, ultraviolet, x-ray, gamma ray

interference

separate light waves can interact by overlapping and either building up(constructive interference) or cancelling each other out(destructive interference)

diffraction

bending of light around an obstacle

Photoelectric effect

The emission of electrons from a metal when light shines on the metal

- Einstein's explanation: E photon = W + Ek

or hv = hv0 + 1/2mu^2

important observations of the photoelectric effect

- for a given metal, there is a minimum frequency(v0) of light needed for the photoelectric effect to occur; think of this as a threshold

- if the light is below the threshold frequency, increasing the light intensity or duration of irradiation has NO EFFECT, so electrons are still not ejected from the metal surface

- once the threshold frequency is met/exceeded, increasing the intensity will cause more photoelectrons to be emitted by the metal surface

- increasing the frequency past the threshold frequency increases the velocity of the ejected electrons, making them fast when they are emitted off the metal surface

- not explained by wave nature of light

How can the photoelectric effect be explained?

- Einstein(1905) explained that the photoelectric effect by treating light as being made up of packets of energy; light is quantized

the energy of the photon must be enough to overcome ________________________

the binding energy/ threshold energy/ work function of an electron or metal

- individual photons from the light source need to be absorbed by individual electrons to eject them

Energy of a photon equations

E = hv

E = hc/λ

v is frequency

Planck's constant(h)

h = 6.626 x 10^-34 J x s

Kinetic energy formula

KE = 1/2 x mass x velocity^2

relating kinetic energy to binding energy through the energy of a photon equation:

hv= hc/lambda = h(v0) + 1/2(mv^2)

electron-volt (eV)

1 eV = 1.60 x 10^-19 J

when atoms or molecules absorb energy, such as heat, light, and electricity, the energy is usually re-emitted as light

Ex: heating a metal until it glows, neon size, fireworks, etc.

- can be explained by the particle nature of light

What is an emission spectra?

- light emitted byy excited atoms can be separated by a prism into the different wavelengths present(pattern[emission spectrum] can be used to identify the atom/molecule)

- different sources of light emit different types of spectra

Rydberg Equation

1/wavelength = R (1/n1^2 - 1/n2^2)

Bohr Model of the (Hydrogen) Atom

- Niels Bohr expanded upon Rutherford's model of the atom to explain why hydrogen emits the specific line of spectra that it does

energy of electron in energy level, n

En = -2.179*10^-18J (1/n^2)

the energy difference between two energy levels (delta E)

Efinal - Einitial

- E photon = delta E = hv = hc/lambda

When delta E is positive

photon/energy is absorbed and electron went from a low energy level to a high energy level

When delta E is negative

photon/energy is released and electron went from a high energy level to a low energy level

Wave nature of matter

- Louis de broglie

- showed relation between mass and wavelength

- said matter should have wave properties

- lambda = h/mv

h = 6.626*10^-34 Js

m = mass of particle in kg

v = speed of the particle in m/s

1927 Double Slit Experiment performed using a beam of electrons

- interference pattern was formed

- conclusion: particles have wave properties and have a wave-particle duality just like light, so you can think of electrons using both a wave and particle image

Heisenberg uncertainty principle

- it is impossible to know exactly both the velocity and the position of a particle at the same time

- you can't observe both wave and particle properties of an electron at the same time

atomic orbitals

- the regions around the nucleus within which the electrons have the highest probability of being found

- described by 3 quantum numbers that designate energy, size, shape and orientation in space of the orbital

principal quantum number(n)

- indicates the relative size and energy of atomic orbitals

- possible values include n = 1, 2, 3... where n is a positive whole number

- the higher the value of n, the further away from the nucleus the electrons are and the higher the energy of the electrons in the energy level

angular momentum quantum number(l)

l = integer values and zero ranging from 0 to n-1

- designates a specific subshell within the principal energy level(n) and designates the shape of the orbitals within the subshell

magnetic quantum number (m sub l)

- an integer that specifies the orientation of an orbital

- possible values: positive and negative whole numbers and zero that range from -l to 0 to +l

magnetic spin number (m sub s)

only two possible values: +1/2 or -1/2

- designates the spin of electrons in the orbital(up or down/clockwise/counter-clockwise)

s orbitals

l = 0, m sub l = 0

- only one 3-D orientation in space

p orbital

l = 1, m sub l = +1, 0, -1

- 3 orientations in space

- lobes align parallel to an x-,y- or z-axis

- 2 lobes = 1 orbital