Chemistry 1 Exam 3

Thermal Energy

Kinetic energy associated with random motion of particles.

Heat

The transfer of thermal energy between two bodies of different temperatures.

Equation for heat

Q = CdT = cmdT

Equation for heat capacity

C = cm

Calorimetry

A technique used to measure the amount of heat involved in a process

What is the specific heat of water?

4.184 J/g*K

Equation for the energy of a system

E = sum(PE) + sum(KE)

Equation for the energy of a reaction

dE = E_products - E_reactants

Equation for change in energy

dE = Q + W

What is positive heat? (+Q)

Heat absorbed.

What is negative heat? (-Q)

Heat released.

What is positive work? (+W)

The work done ONTO an object.

What is negative work? (-W)

The work done BY an object onto something else.

Describe the work of “X does work on Y”

W_x decreases, W_y increases

What is enthalpy?

Chemical change at a constant pressure

What is the equation for change in enthalpy?

dH = dE + PdV

What is the equation for change in enthalpy for a chemical reaction?

dH = H_products - H_reactants

Describe an exothermic process.

Heat is released as a product. dH < 0

Describe an endothermic process.

Heat is absorbed as a reactant. dH > 0

What is a thermochemical equation?

A balanced chemical equation that includes the heat of the reaction.

In a thermochemical equation, what does positive dH indicate?

An exothermic reaction.

What is the equation for dH released given moles?

dH_f = n * dH

What is Hess’s Law of Summation?

dH_f = dH_1 + dH_2 + dH_3 + …

Under what condition is gas stable enough to use the standard heat of reaction?

P = 1 atm

Under what condition are aqueous solutions stable enough to use the standard heat of reaction?

M = 1M

Under what condition are pure elements stable enough to use the standard heat of reaction?

M = 1M

T = 25 Celsius

What is the standard heat of reaction for elemental forms?

0

What are the elemental forms of gases?

H2, N2, O2, F2, Cl2, He, Ne, Ar, Kr, Xe

What are the elemental forms of liquids?

Br2, Hg

What are the elemental forms of solids?

C (graphite), S8 (rhombic), I2, P4 (white), most metals

What is the equation for the speed of a wave?

c = vx, where v = frequency and x = wavelength

What is amplitude?

The height of a wave’s crest.

What is the speed of light?

c = 3 * 10^8 m/s

What are the EM waves from lowest to highest wavelength?

Gamma, X-Ray, Ultra-Violet, Visible, Infrared, Microwave, Radio

What are the EM waves from lowest to highest frequency?

Radio, Microwave, Infrared, Visible, Ultra-Violet, X-Ray, Gamma

Describe refraction.

When a wave strikes a boundary at an angle, the immediate change in speed results in a change in direction.

Describe diffraction.

A wave striking the edge of an object will bend around it.

What is Blackbody Radiation?

The emission of visible light when a solid is heated very high.

What is the equation for the energy from a wave?

E = nhv, where n = quantum number, h = planck’s constant, and v = frequency

What is the equation for change in quantum number?

dn = c/(vx), where c = speed of light, v = frequency, and x = wavelength

What is Planck’s Constant?

h = 6.626 × 10^-34

What is the photoelectric effect?

When a light of sufficient brightness shines on a metal, current flows because electrons are transferred to the metal surface.

What is the Rydberg Equation?

(1/x) = R( (1/n_1) - (1/n_2) ), where R = 1.096776 × 10^-7

What is the equation for the energy of an atomic level?

E_n = -(k * z²) / n², where k = 2.179 10^-18

What is the equation for wavelength, derived from E = mc²?

x = h / mc

What is Heisenberg’s Uncertainty Principle?

It is impossible to know both the position and momentum of a moving particle at the same time.

dx * du * m >= h/4(pi), where x = position, u = uncertainty in momentum, and m = mass

What happens to emittance and absorbance has n increases?

Absorbance increases, emittance decreases

What shape is the orbital when Angular Momentum Quantum Number L = 0?

Sphere, orbital s

What shape is the orbital when Angular Momentum Quantum Number L = 1?

Dumbell, orbital p

What shape is the orbital when Angular Momentum Quantum Number L = 2?

Lobed Clover, orbital d

What shape is the orbital when Angular Momentum Quantum Number L = 3?

8 Lobes

What does the magnetic quantum number m_L describe?

The orientation of an atomic orbital

What does the spin quantum number m_s describe?

The direction of an electrons magnetic field. Either +0.5 or -0.5

What does the principle quantum number n describe?

The level of the orbital.

What is the equation for the max number of electrons give max orbital level n?

e = 2n²

What is the equation for the number orientations (m_L) possible for an orbital?

m_L = 2^n - 1, where n = orbital level

What are the characters used for orbital names, in order?

s, p, d, f

How is effective nuclear charge (Z_eff) affected by distance from the nucleus?

The further a nuclear charge is, the lower the effective nucelar charge.

Using the Aufbau Principle, what is the electron configuration for an element with 15 electrons?

1s² 2s² 2p^6 3s² 3p³

What is the format of a condensed electron configuration?

[noble gas closest to element’s electrons] (electron configuration for the valence electrons)

What is the condensed electron configuration of sodium?

Na(z = 11) = [Ne]3s^1

What are the two exceptions to the electron orbital rules?

Bromine and Copper

Br: [Ar]3d^10 4s² 4p^5

Cu: [Ar]3d^10 4s^1

In what order are electrons lost?

Outer (valence) electrons are lost first.

How do you get metallic radius?

0.5 the closest nuclei of adjacent, individual atoms in a crystal of metal

How do you get covalent radius?

0.5 the shortest distance between nuclei of covalently bonded nonmetals.

What is the relationship of atomic radius on the periodic table?

Increases going down groups and left across periods.

What is the relationship of ionization energy on the periodic table?

Increases going up groups and right across periods.

What is the relationship of metallic behavior on the periodic table?

Increases going down groups and left across periods.

What is the relationship of electron affinity on the periodic table?

Increases going up groups and right across periods. (With many exceptions)

What is ionization energy? (IE)

The energy (in kJ) required to remove 1 mol electrons from 1 mol gas. It removes valence electrons.

How does IE change as valence electrons are removed?

IE increases, and spikes greatly when removing a valence shell.

What is the relationship of ionic radius with the periodic table?

Increases down a group. Decreases to the right across a period for cations. Increases to right across a period for anions.

What is an isoelectric series?

A series of ions that have the same electron configuration.

What is the relationship of effective nuclear charge with the periodic table?

Decreases going down groups and right across periods.

Why do atoms bond?

To lower their potential energy.

What elements form ionic bonds, and what happens to the electrons?

Nonmetals and metals. Electrons are transferred from one to the other.

What elements form covalent bonds, and what happens to the electrons?

Nonmetals. Electrons are shared between both.

What elements form metallic bonds, and what happens to the electrons?

Metals. Electrons are pooled between both.

Describe ionic compounds.

Hard, rigid, and brittle.

Has a high melting point.

Does not conduct well as a liquid.

Describe the distance between atoms in a covalent bond.

The electrons are attracted to the positive nucleus, but the atoms are also repelled by the positive nuclei. They are held at a distance that balances their attractive and repulsive forces.

What is electronegativity?

The ability of an atom to attract a shared electron pair.

What is a polar covalent bond?

A covalent bond where electrons aren’t shared equally, so some electrons remain closer to an atom.

What is the most electronegative element?

Fluorine

What is the relationship of electronegativity (EN) with the periodic table?

Decreases going up groups and left across periods.

How do you determine which polar covalent bond is more polar?

The covalent bond with the highest dEN

How can electronegativity (EN) describe covalent vs an ionic bond?

dEN < 0.4, nonpolar covalent
0.4 < dEN < 1.7, polar covalent

dEN > 1.7, ionic

What is the octet rule?

When atoms bond, they lose, gain, or share to attain 8 valence electrons,

What are the steps for drawing the Lewis Structure of a Molecule?

1.) Put the least electronegative atom in the center

2.) Determine the total valence electrons

3.) Draw single covalent bonds (each bond is a shared pair of 2e)

4.) Distribute lone pairs to fill valence electrons

What if there are too many electrons to achieve an octet in a molecule?

The molecule will take on multiple bonds originating from the central atom.

What are the exceptions to the Octet Rule?

H, Li, Be, B, and some nonmetals from period 3 or higher.

What elements have 2 valence electrons?

Helium and Lithium

What elements have 4 valence electrons?

Beryllium

Which elements have 6 valence electrons?

Boron

Which elements may have >8 valence electrons? (an expanded shell?)

Nonmetals from period 3 or higher.

Notable nonmetals: P, S, Cl

Notable compounds: PCl5, SF6, ClF3, XeF6

What are molecules with an odd number of electrons called?

Free radicals

What are the steps to draw a resonance structure?

1.) Place the least electronegative atom in the center

2.) Get the total electrons

3.) Build the Lewis Structure

4.) Make new renditions for each configuration of bonds

What is the equation for fractional bond order?

(bonds) / (pairs of bonded atoms)

What is formal charge? (FC)

The charge of an atom if all electrons were shared equally.

What is the equation for formal charge? (FC)

1.) FC = (valence electrons) - (lone electrons) - (bonds)

2.) FC = (valence electrons) - (unshared electrons) - (0.5 * shared electrons)

What is bond order?

The number of electron pairs shared by a pair of bonded atoms.

The number of bonds.