Chem 141 final Exam

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The wavelength of the electron is 1.45x10⁻⁹m which is closest in size to a..

diameter of a carbon nanotube

molecules that are compounds

more than one molecule

translation

moving in one direction

gravitational force

only attractive force

You (a human being) are what kind of system?

open

Photoelectric effect

shows that there is a threshold frequency below which no electrons are ejected regardless of how much we increase the intensity -light photons are shined on a piece of metal and electrons are emitted

law

describes the phenomenon tells you WHAT

atoms that are elements

true, an element is made up of the same atom

3 centers of electrons

-120° -sp² -0 lone pairs=trigonal planar geometry and shape -1 lone pair= trigonal planar geometry and bent shape

bonding in diamond

-4 carbon bonds -sp³, geometry=tetrahedral, 109°

polar bonds

-when two atoms of different electronegativities bond, the electrons are not shared equally, results in a dipole

moles to grams

# of moles X (molar mass in g/1 mol)= grams

For the process shown in the diagram the ∆H is:

+ because heat is added to the reaction

For the process shown in the diagram the ∆S(entropy/arrangements) is

+ because in the gas phase the most arrangements can be created

2 centers of electrons

-0 lone pairs -sp -linear geometry -linear shape -180°

Why are metals shiny?

-Because they absorb photons and re-emit them -metals have molecular orbitals that are very close together in energy. They can absorb almost any wavelength of light because the gap b/w the leaves is negligible(unimportant). The absorbed light can then be re-emitted.

bonding in graphite

-C-C-C -sp², geometry=trigonal planar, 120°

hydrongen bonding interactions

-Intermolecular forces, not bonds 1. First must contain H covalently bonded to O, N, or F 2. must have O, N, or F atom with lone pair -interactions are very strong -also have dipole-dipole and LDFs

Why do metals tend to form cations while nonmetals form anions?

-It is easiest to achieve noble gas configuration by removing valence electrons from metals (which have few valence electrons) and adding them to nonmetals (which have many valence electrons) -Electrons are more attracted to the nuclei of non metals because they have higher effective nuclear charges

endothermic

-if the change in H is positive -heat goes into the reaction and the surroundings get colder Ex: sweat evaporating

the ionization energy of carbon (C) is:

-Smaller than that of fluorine (F) -The effective nuclear charge of carbon is smaller, so the valence electrons feel weaker pull from the nucleus -In carbon, the electron being removed is farther from the nucleus

What is the reasoning to support the claim that graphite will conduct electricity but diamonds will not conduct electricity?

-Some of the valence electrons are delocalized (free to move) in the pi bond that extends across the entire graphite structure -valence electrons are localized and cannot freely move in the covalent bonds in diamond

electronegativity

-ability to attract electrons to itself in a bond -depends on effective nuclear charge and size of orbitals -same trend as effective nuclear charge -increases across a row -decreases down a group

solid-energy of motion

-absent translation -very limited rotation -free vibration

Molecular orbital theory

-atomic orbitals combine to form an equal number of molecular orbitals -each orbital can contain up to two electrons -electrons in bonding orbitals stabilize the system -electrons in antibonding orbital make it less stable - electrons are delocalized

valence bond theory

-atomic orbitals overlap to form a bond -the greater the overlap, the stronger the bond -each bond made up of two electrons -electrons are localized in the bond

As two isolated He atoms move from far apart to the distance where they are most stable, the potential energy of the system will...

-increase because the electrons from one atom will repel the electrons from the other atom -PE ↑=repulsion -PE↓=attraction

simple ionic compounds

-contain a metal and non metal -metal has a low electronegativity and non metal has high electronegativity -metals form cations and nonmetals form anions -ionic compounds are neutral

Absorption spectra

-continuous spectra where electrons/energy are absorbed -light is missing -electrons occupy the ground state

What is the most stable interaction between two Xe atoms and when the interaction is broken, energy is?

-covalent bond -absorbed

path functions

-depend on how the change takes place -lower case letters Ex:heat and work

state function

-depending only on the initial and final states, does not depend on path taken Ex:the elevation of the campsite is a state function and it is independent of the paths taken to reach it and density, internal energy, enthalpy, entropy -upper case letters

thermal energy

-depends on how much material you have -movement associated with motion of particles (unit is joules)

temperature

-depends on the average KS of the particles -measure of "hotness" -direction of thermal energy goes from hot to cold -doesn't change until after the phase change is complete

Diamond

-does not conduct electricity (Electrons are localized b/w the two nuclei that participate in the bond. The electrons cannot more out of the area and are not mobile. To conduct electricity, charged particles must be able to move freely in molecular orbitals) -has a very high melting point (To melt diamond and allow the particles to move relative to one another C-C covalent bonds must be broken. Substances that exist as molecules tend to have lower melting points b/c the IMFs are overcome rather than covalent bonds)

Determining if polar bond

-draw lewis structure -draw arrows toward the most electronegative atom -if the arrows are facing each other, then the bond is polar -if the arrows are facing away from each other then they cancel out and there is no dipole

What is the shape of the hydronium ion, H₃O⁺?

-draw lewis structure -trigonal pyramidal b/c it loses one electron so there is only one lone pair

What is the electron center geometry and hybridization on the S atom in SF₂

-draw lewis structure -tetrahedral and sp³

What intermolecular forces would exist between molecules of CH₂Cl₂?

-draw lewis structures -london dispersion forces -dipole dipole interactions

Is BF₃ a polar molecule?

-draw the lewis structure -No, because the bonds between B and F are polar and the molecular shape of BF₃ is trigonal planar, therefore the electronegativity will pull in opposite directions and the bond dipoles will cancel out

What is the electron center geometry and shape of the molecule H₂S?

-draw the lewis structure -tetrahedral and bent

emission spectra

-electrons are excited up to higher energy -then drop and create a photon -photons create colored lines, the lines correspond to the frequencies of photons of light emitted

First law of thermodynamics

-energy cannot be created or destroyed (but it can be transferred or transformed)

When a covalent bond is formed between two hydrogen atoms...

-energy is released -a molecule is formed

Second law of thermodynamics

-for any change the total entropy of the universe must increase -the state of entropy of the entire universe, as an isolated system, will always increase overtime and changes in entropy of the universe can never be negative

What is the formal charge on each atom in the amide ion, NH₂-?

-formal charge=# of valence electrons in the neutral atom-# of bonds-# of free electrons - N=5-2-4=-1 - H= 1-1-0=0

Gas-energy of motion

-free translation -free rotation -free vibration

Diamond properties

-hard(3D network of strong bonds, you would have to break bonds to disrupt a crystal) -high mp/bp (same as hard) -does not conduct electricity(electrons are located in bonds between atoms-not free to roam. There is a large "band gap" between the bonding and antibonding orbitals) -translucent(light passes through or is reflected. To absorb light an electron must be promoted to a higher energy level.)

Graphite properties

-high mp -soft -slippery(sheets can slide over each other/only held together by LDFs) -grey/shiny(because it can absorb and emit photons of many wavelengths (just like metals) -conducts electricity(because electrons can move freely over the entire sheet within its delocalized pi MOs)

exothermic

-if the change in H is negative -heat goes out of the reaction and the surroundings get hotter Ex:wood burning, water freezing, chemical hand warmer

Entropy

-measure of the number of possible arrangements for a given state -more arrangements=higher probabilty

anions

-negatively charged -larger than corresponding atom -form when nonmetals gain electrons -charge usually corresponds to gain of electrons needed to fill the next full shell (noble gases)

trend of effective nuclear charge

-opposite of atomic radius -increases across a row -decreases down a group

cations

-positively charged -smaller than corresponding atom -form when metals lose electrons -form because energy is released when ion-ion interactions are formed

dipole-dipole

-present in polar substances -typically stronger than LDF for molecules of the same size -

liquid-energy of motion

-restricted translation -less free than gas rotation -free vibration

4 centers of electrons

-sp3 -0 lone pair= tetrahedral geometry and shape, 109° -1 lone pair=tetrahedral geometry and trigonal pyramidal shape, <109° -2 lone pairs= tetrahedral geometry and bent shape, <109°

London dispersion forces

-temporary dipoles -depends on size, surface area, and shape of molecule -present in all substances solid and liquid states -if nonpolar this is the only intermolecular force present

If the molar mass of the gas increases, what happens to the average velocity?

-the average velocity decreases -larger gases have smaller velocity

When gas molecules collide why don't they stick together?

-the molecules don't stick together because have enough energy to overcome the attractive interactions

sigma bonds

-they form end to end overlap of atomic/hybrid orbitals -free rotation is allowed around the bond -single bonds=sigma bond -double bonds=one sigma and one pi -triple bond=one sigma and two pi

Pi bonds

-they form side to side overlap of atomic orbitals -free rotation is not allowed around the bond -double bonds=one sigma and one pi -triple bond=one sigma and two pi

CH₄(g)+2O₂(g)→2H₂O(l)+CO₂(g) How many molecules of CH₄ will remain at the end?

0

How many core and valence electrons does carbon have?

2 core, 4 valence

How sigma and pi bonds do the carbon atoms form in the diagram.

3 σ bonds and 1 π bond

What is the mass of 3.5 moles of Cl₂?

248 grams

CH₄(g)+2O₂(g)→2H₂O(l)+CO₂(g) How many molecules of CO₂ will be produced?

3

CH₄(g)+2O₂(g)→2H₂O(l)+CO₂(g) How many molecules of O₂ will remain at the end?

3

CH₄(g)+2O₂(g)→2H₂O(l)+CO₂(g) How many molecules of H₂O will be produced?

6

A)X has a longer stronger interaction than Y B)X has a shorter weaker interaction than Y C) X has a shorter stronger interaction than Y D) X has a longer weaker interaction than Y

A

Would you expect methane CH4 or difluoromethane (CF2H2 to have the higher boiling point? Why?

CF₂H₂ because it is a polar molecule that can form dipole-dipole interactions

What is a stable system formed at?

A potential minimum that would require energy input to change

What is wrong with the following statement? As the ball falls its potential energy decreases.

A single object cannot possess potential energy and there is no mention of a field

Which of the following contains the largest number of molecules?

A) 15.0 g Br₂ B) 15.0 g Cl₂ C) 15.0 g O₂ D) they all have the same number C) 15g O₂ because the mass of O₂ is the smallest so more O₂ molecules can fit into 15 g

Why do covalent bonds form?

Because electrons from one atom are attracted to the nucleus of another atom and the formation of a bond results in a stable system that would require the input of energy to change

If you put bromine liquid in a pan on the stove and heat it up, the bromine will boil. What is the mechanism (process) by which this happens?

As more bromine molecules get more energy, they can overcome the electrostatic forces of attraction and the bromine molecules can escape into the gas phase.

Thomson's plum pudding model

Argued that electrons are embedded in the atom although couldn't determine location of the electrons or if there were any other particles in the atom

If you put bromine liquid in a pan on the stove and heat it up, the bromine will boil. What is the mechanism by which the boiling process happens?

As more bromine molecules get more energy, they can overcome the electrostatic forces of attraction and the bromine molecules can escape into the gas phase

Thomson observed that the type of metal used for the cathode did not affect the behavior of the cathode ray. What claim does this piece of evidence support?

All atoms contain electrons

Which of these are true: I. All neutral atoms and molecules attract each others. II. London dispersion forces increase as the size of the electron cloud increases. III. It takes energy to overcome the attractions between particles. IV. Energy is released to the surroundings when atoms form a stable interaction.

All of these statements are true

Boron nitride is the second hardest substance known(after diamond). It has a very high melting point, but does not conduct electricity. What types of bonding do you think are present in boron nitride?

An extended network of boron and nitrogen atoms held together by covalent bonds

If the intensity of a beam of light is increased, this would correspond to:

An increase in the number of photons (considering light as a particle) and an increase in the amplitude of the wave (considering light as a wave)

An isolated helium atom is shown. In what state of matter is helium shown in this diagram?

An isolated atom doesn't exist in a state

The potential energy of the system as two atomic nuclei (eg H⁺) approach each other and fuse to form ²H?

At far distances, the nuclei are affected by the electrostatic force of repulsion, which causes the PE to increase as the distance decreases. Once the nuclei get very close to each other, the strong nuclear force takes over. This is an attractive force, which means the PE will decrease as the nuclei get closer to each other

Rutherford's planetary model

Atoms are composed of mostly empty space. His gold foil experiment showed that there are positively charged atoms because the foil deflected some of the alpha particles. He also noted that electrons orbit around the nucleus and eventually spiral out onto the nucleus

You are asked to compare the interaction between atoms of two substances, substance X and substance Y. When you look at the graph showing how potential energy changes as distance between the atoms changes, you notice that substance Y has a much deeper potential energy well than substance X. From this information, you conclude..

Atoms of Y interact to form covalent bonds and covalent bonds are stronger than London Dispersion forces and require more energy to break

Why do atoms start to repel each other when they become very close together?

Because the atoms are moving together despite the repulsive force (atoms are against the force), causing the PE to increase

Which of the following would you predict to have the smallest ∆Hvap? (The heat required to change one molecule of substance from a liquid phase to a gas phase (vaporize)? A)CH₃OH B)CH₄ C)OF₂ D)NaF

B)CH₄ because it only has LDFs which takes the least amount of energy to overcome

Which has the highest entropy (per mole)? A)H₂O(s) B)H₂O(g) C)H₂O(l) D) all have the same entropy

B)H₂O(g) -most arrangements can be made in the gas phase

if the same amount of thermal energy were transferred to equal masses of water, copper, granite and ethanol, which substance would reach the highest temperature? A)water(Cs=4.18J/g°C) B.Copper(Cs=0.385J/g°C) C.Granite(Cs=0.7 J/g°C) D.Ethanol(Cs=2.42J/g°C) E. they would all reach the same temperature since an equal amount of thermal energy is transferred to an equal mass of each

B.Copper(Cs=0.385J/g°C) because it has the smallest amount

Yellow light ejected electrons from a piece of potassium metal. If the metal in the photoelectric effect experiment changed to lithium, what type of light would you predict is needed to eject the electrons?

Blue light because the valence electron in Li is closer to the nucleus than the valence electrons in K. Li would need a higher energy photon to overcome the stronger force of attraction.

2 ¹²C→²³Mg+¹n+energy What is this reaction an example of?

a nuclear fusion reaction because small nuclei are coming together to make a larger nucleus

Which do you predict to have a higher boiling point and why? CH₃OH CH₃CH₂CH₂OH

CH₃CH₂CH₂OH because the london dispersion forces are stronger because the molecule is larger, so more energy is required to overcome them

Which of the following substances would you expect to have the highest boiling point? I)CH₃CH₂NH₂ II)CH₃CH₂CH₃

CH₃CH₂NH₂ because the strongest attractive force that is over is hydrogen bonding

Fluorine (F₂) and Chlorine (Cl₂) both exist as diatomic molecules. Fluorine has a boiling point of 85.03K, and chlorine has a boiling point of 239K. Draw a graph showing the change in PE as two molecules of fluorine and chlorine get closer to eachother

Chlorine has a stronger interaction than fluorine because chlorine has a greater mass which creates a greater intermolecular distance and higher boiling point

Rutherford's experiment

Claim: the atom is mostly empty space with a very small dense nucleus Evidence: Most alpha particles went straight through, only a few were deflected Reasoning: the positively charged alpha particles were deflected by the repulsive interaction with the positive nucleus; since only a few were deflected the nucleus must take up a very small volume of the atom

Which do you think will have a higher boiling point and why? -Cl₂ -F₂

Cl₂ because the LDFs between molecules are stronger, requiring more energy to overcome

Which is the smallest? A) an atom B) a cell C) a proton D) an electron

D) an electron

A substance has a low melting point. It does not conduct electricity either when melted or as a solid. It is most likely: A)diamond B) copper C)Calcium oxide D)paraffin (C₃₁H₆₄)

D) paraffin (C₃₁H₆₄) because only LDF are present

When two nuclei move extremely close to each other (within the distance of nucleus), the potential energy....

Decreases because the strong nuclear force between the nuclei is attractive

Consider a container of xenon atoms where two xenon atoms of interest are interact (the system) and are surrounded by other atoms. The surrounding Xenon atoms have more energy than the two xenon atoms in the system. Which direction would you predict the energy would be transferred and what would happen?

During a collision, energy will be transferred from the surrounding xenon atoms to the system of two xenon atoms and the stable interaction will be overcome.

What wavelength of light would break an O=O bond (it takes 8.3x10⁻¹⁹J to break one O=O bond)?

E=hv 8.3x10⁻¹⁹J=6.626x10⁻³⁴(v) v=1.2526x10¹⁵Hz 3.0x10⁸m/s=1.2526x10¹⁵Hz(λ) λ=2.4x10⁻⁷m λ=2.4x10⁻⁷m(10⁹nm)=240nm

Thomson's cathode ray tube experiment showed that the beam of emitted particles was deflected by charged particles. Thomas used this evidence to support his claim that:

Electrons carried an electrical charge

Thomson's experiment allowed him to make the claim that all atoms have a sub structure and contain smaller particles (electrons) embedded in the structure of the atom. What evidence and reasoning allowed him to make this claim?

Evidence: Electrons were ejected from the cathode, regardless of what metal the cathode was made of. Reasoning: Since the particles are emitted regardless of the nature of the nature of the cathode, they must be part of the sub-structure of the atom

Elements are composed of small indivisible, particles called atoms

False, atoms have a substructure

Which reaction requires the most energy?

F⁺→F²⁺+e⁻ (higher Zeff, so harder to remove electron) -Effective nuclear charge(Zeff)=# of protons-# of core electrons -when electrons are reduced, the repulsion b/w the electrons decreases=decrease in the radius which causes the strength of the attraction to increase in the amount of energy to remove an electron

Rank of electromagnetic radition

High energy: gamma-ray, x-ray, UV, visible, IR, microwave, long wave: low energy

Dalton's billiard ball model

His model of the atom consisted of a solid nucleus with no electrons. Photons are reflected off the atom.

Which of the following are correct statements? I)Covalent bonds are interactions within molecules II)Covalent bonds are interactions between separate molecules III) LDFs are interactions between separate molecules IV) LDFs are within molecules

I)Covalent bonds are interactions within molecules III) LDFs are interactions between separate molecules

Which diagram best represents the band structure for sodium and can be used to explain its electrical conductivity?

I, because sodium conducts electricity because electrons can move freely into empty molecular orbitals

Which diagram best represents the band structure for sodium (Na) and can be used to explain its electrical conductivity?

I, sodium conducts electricity because electrons can move freely into empty molecular orbitals

Which of these are true: I. Covalent bonds are interactions within molecules II.Covalent bonds are interactions between separate molecules III. LDFs are interactions between separate molecules IV. LDFs are within molecules

I. Covalent bonds are interactions within molecules III. LDFs are interactions between separate molecules

Three methanol molecules are shown. Which of the labeled interactions are hydrogen bonding interactions

II only

Which of the following would you expect to have a measurable melting point? I) an isolated atom II) a 5 gram block of gold III) both I and II have measurable melting points

II) A 5 gram block of gold because in order to melt, there must be more than one particle present so that the forces between the particles can be overcome

Two lewis structures are shown. Are these molecules the same or are they isomers?

Isomers because the molecules have the same formula but different atom connectivity

The boiling point of iodine (I₂)is much higher than the boiling point of helium (He). Why?

I₂ has a larger electron cloud than He, so more energy is required to overcome the stronger London Dispersion Forces

Which of following substances conducts electricity in the liquid state, but not the solid state? KBr or Na

KBr because charged ions are free to move relative to one another in the liquid state but not the solid state

Opposite charges are attracted to each other in proportion to the product of their charges and inversely proportional to the square of the distance between them. This statement is a...

Law because it describes the phenomenon

When oxygen boils...

London dispersion forces between the O₂ molecules are overcome

Consider the following four objects: M1=5g M2=5 g M3=10 g M4=10 g Assume that the objects are separated by equal distance. Between which two objects is the gravitational force the strongest?

M3 and M4

The first six ionization energies for an element in the third period are shown in the graph. Which element is this?

Mg -b/c the biggest change is between the 2nd and 3rd ionization energies and magnesium is the 2nd element in the third period. You always pick the element that comes first when the jump occurs.

Which has a larger atomic radius? Mg or Ar and why?

Mg, because its valence electrons are not as strongly attracted towards the nucleus as those in Ar. The Zeff on Mg is smaller. On Ar the electrons are more attracted causing the cloud to shrink until e-e repulsions come into effect

What is most likely the formula for a compound between magnesium and bromine?

MgBr₂ because Mg²⁻Br⁺¹ and flip numbers

Consider the isoelectronic (they all have the same number of electrons) species Na⁺, Mg²⁺,Ne, F⁻. Which of these has the smallest radius?

Mg²⁺ (highest proton to electron ratio and highest Zeff) -they all have the same electrons but different number of protons -Zeff(effective nuclear charge)=# of electrons- # of core electrons -atoms with a high ENC hold on to their atoms more tightly which is why electrons are strongly attracted to the nucleus

For a gas at room temperature..

Molecules are moving at different speeds because collisions transfer energy between molecules

Which of the following compounds would most likely have the higher melting point, NaF or CsBr? Why

NaF, because the ions are smaller making the attraction between them stronger so that more energy is required to overcome these interactions

A molecular orbital diagram for B is shown to the right. Will Be exist as a molecule according to molecular orbital theory?

No because electrons in bonding orbitals make the species more stable and electrons in antibonding orbitals make the species less stable and the stabilization form the electrons in bonding molecular orbitals is cancelled out by the destabilization caused by the electrons filling the antibonding molecular orbitals

Glucose (C₆H₁₂O₆, molar mass 180g/mol) reacts with oxygen (O₂, molar mass 32 g/mol) to produce carbon dioxide (CO₂, molar mass 44g/mol) and water (H₂O, molar mass 18g/mol). C₆H₁₂O₆→6CO₂+6H₂0 During this reaction 10g of C₆H₁₂O₆ reacts with excess oxygen to produce 8g of water. Evaluating the percent yield you obtained for this reaction, is this a good yield if you were expecting to get an 80 to 90% yield for the reaction?

No this is not a good yield because there is more product than could possibly be formed and so there must be an impurity in it.

A molecular orbital diagram for beryllium (Be) is shown. Will beryllium exist as a molecule according to molecular orbital theory?

No, electrons in bonding orbitals make the species more stable and electrons in antibonding orbitals make the species less stable and the stabilization from the electrons in bonding molecular orbitals is cancelled out by the destabilized caused by the electrons filling the antibonding molecular orbitals

Consider the elements sulfur and oxygen. Which element is more electronegative? O or S

O, because the bonding electrons are closer to the nucleus

For a given photocell (a device that uses the photoelectric effect to generate electricity), blue light will eject electrons but red light will not. Why?

Photons of blue light each have enough energy to eject one electron

Iodine exists as molecules of I₂, and silicon dioxide exists as an extended network of silicon oxygen bonds (similar to diamond). They both are solids at room temperature, but which do you think has the higher melting point and why?

Silicon dioxide, because it is a compound

Which piece of evidence supports that claim that all matter and energy in the Universe were once concentrated in a single point (singularity)?

The absorption spectra of galaxies are red-shifted because those galaxies are moving away from us

In Rutherford's gold foil experiment, the majority of the alpha particles went straight through the gold. Why was that?

The atom is mostly empty space, so nothing manipulated the path of the alpha particles

Why do two isolated atoms attract each other as they approach and why do they repel if they get too close together?

The attractive coulombic interaction causes thee atoms t approach due to the partial positive and negative sides of atom created by instantaneous dipole however once the atoms get too close the atoms begin to overlap and the atoms create a repulsive force and repel

What causes the change in potential energy when the two helium atoms move from point Z to point Y in the figure?

The attractive force

What can we use to predict whether atoms interact through covalent bonds or ion-ion interactions (ionic bonding interactions)?

The electronegativity difference between the atoms -if the atoms have similar electronegativities, valence electrons will be shared between nuclei. When the electronegativities are very different, the valence electrons will be completely transferred from the less electronegative atom to the more electronegative atom

How would the strength of the electrostatic force change if the distance between two charged objects increased?

The electrostatic force would become weaker

How would the energy change as two helium atoms move from point Z to point Y in the figure?

The kinetic energy increases, the potential energy decreases, the total energy doesn't change

Helium exists at room temp as a monatomic gas(He) and hydrogen exists in room temperature as a diatomic gas (H₂)...

The number of molecules in one mol of H₂ is greater than the number of atoms in one molecule of He

Compare a 3s orbital to a 3p orbital

The orbitals have different shapes and different energies

The potential energy as two positive atoms approach each other and why does the potential energy change in the way shown

The positive charges are moving toward each other against the repulsive force that exists between them

What happens on the molecular level when thermal energy (heat) is added to increase the temperature of water from 10°C to 50°C?

The water molecules speed up, and collide with the thermometer, transferring energy to the thermometer. this energy causes the mercury atoms in the thermometer to vibrate more, and the liquid expands (thus showing an increase in the temperature scale)

One part of Dalton's Atomic Theory states: Compounds are formed by combinations of atoms from two or more elements

This is true because by definition a compound must have at least two types of elements

Water (H₂O) and dihydrogen monosulfide (H₂S) have similar chemical formulas and structure. At room temperature, H₂O is a liquid and H₂S is a gas. What is the difference?

Water is more polar and thus the attractive forces between water molecules are stronger than the attractive forces between H₂S molecules.

isomers

What is the same: number of each type atom and chemical formula What is different: connectivity b/w atoms and properties

When and where were the carbon and oxygen atoms in your body created?

Within stars and stellar explosions

Consider the following velocity distributions for different gases at the same temperature. Which gas has the smallest velocity? A) Ne B) Ar C) Kr D) Xe

Xe- because it has the largest mass which causes a decreases in velocity

Does the planet Venus have phases like the moon? Is this question a scientific question?

Yes because it can be tested and answered through observations and experiments.

Can graphite conduct electricity?

Yes, graphite exists as 2D sheets of sp² hybridized C atoms. Unhybridized p orbitals can interact to form delocalized pi orbitals that extend throughout the sheet. Electrons in the pi network can move freely.

In the lab you mix together 10g of 10g of ammonia with 15g of oxygen to form nitric oxide with water. You are asked to produce 25g of nitric oxide (NO). Do you have enough starting materials to produce the desired amount of NO and why? Also what is the maximum amount of (in grams) of nitric oxide that would be produced during this reaction?

You must change 10g NH₃ to g of NO and 15g O₂ to g of NO and then determine which is the limiting reactant -there is not enough of either reactant to produce 25g of NO -11.3 g NO is the maximum amount that can be produced

What is the electron configuration of Se

[Ar] 4s²3d¹⁰4p⁴

When a covalent bond is formed between two atoms

a collision must happen to transfer energy out of the system

How many core and valence electrons does magnesium (Mg) have?

a) 10 core and 2 valence

What could you use as evidence to support the claim "energies of electrons are quantized"?

absorption and emission spectra

percent yield

actual/theoretical x100

Which part of Dalton's theory can be proven false by the existence of isotopes?

all atoms are indivisible and indestructible

As two isolated He atoms approach eachother

as they approach KE↑ then ↓ PE↓ then ↑ sharply

Atomic radius trend

atomic radius ↓ across row atomic radius ↑ down a group ↑electrons, ↑radius

electrostatic/electromagnetic

attractive and repulsive force -requires two or more objects

London dispersion forces and covalent bonds are both...

attractive interactions and they both release energy when they are formed

Why is nuclear fusion not a viable option for generating energy at the moment?

because of the high energy requirement to overcome the coulombic repulsion of the nuclei

why do bonds form between atoms?

because the electron(s) on one atom are attracted to the nucleus of the other atom. When the attractive force equals the repulsive force (PE minimum), the bond is formed

nuclear fission

breaking a nuclei apart, neutrons released in fission can induce more fission (splitting of large atom into 2 or more smaller ones

What is the wavelength of light that has a frequency of 3.0x10⁹Hz?

c=λv C=3.0x10⁸m/s 3.0x10⁸m/s= 3.0x10⁹Hz(λ) λ=0.1m=10cm

open system

can transfer energy and matter (biological system) -a person eating a sandwich

Why do ionic compounds conduct electricity in the liquid state, but not in the solid state?

charged ions are free to move relative to one another in the liquid state

What is the best explanation as to why copper is ductile (can be pulled into wires)?

delocalized electrons hold the copper together as the nuclei move relative to each other

Identify the types of intermolecular forces present in the diagram

dipole-dipole and london dispersion forces -the molecule is polar because oxygen is the most electronegative (it is the farthest to the right)

Atomic absorption spectra are caused by:

electrons moving to higher energy levels and absorbing photons of energy equal to the energy difference between the levels

radioactive decay

emitting particles, nucleus emits or captures particles or energy in the form of electromagnetic radiation

moving from solid→liquid→gas

energy is absorbed

moving from gas→liquid→solid

energy is released

specific heat capacity

energy required to raise 1 g by 1°C (or 1K) -higher specific heat=more energy required to raise temp -how much energy it takes to change the energy of a substance

molar heat capacity

energy required to raise 1 mol by 1°C (or 1K)

theory

explains the phenomenon tells you WHY

The atomic theory of matter is an example of a scientific theory. What distinguishes it from a scientific law such as the law of gravity? The atomic theory:

explains the underlying cause of a range of phenomena

atoms that are compounds

false, not possible

The boiling point of hydrogen is 20K. Describe the particles present in a container of hydrogen at 25K

gaseous hydrogen molecules

Enthalpy H

heat absorbed or emitted during a reaction under constant pressure

Relationship between wavelength, frequency and velocity

higher frequency=higher velocity=shorter wavelength

Which of the follo transitions would be most likely to result from the absorption of a photon of the highest frequency?

highest frequency=highest energy -largest change in energy for absorption is the longest upward arrow.

Hydrogen bonding

hydrogen can only bond with N, O, F -has to have an interaction with lone pair

As two protons move toward each other, the potential energy of the system will...

increase because of the repulsive force between the like charges

relationship of LDF

increase the size of atom then increase in LDF and when you increase the size it is harder to break the bonds

If a reaction occurs between a compound that has a lemon smell and one that has a rose smell what will the product smell like?

it is impossible to predict the smell of the product because the properties of the new substances depends on its molecules structure (the properties are emergent)

A property of metals at the atomic level is described below. Which property does describe? "Metal atoms are packed in layers that can move relative to one another. When the nuclei move relative to one another, the valence electrons act as a glue holding them together."

metals are ductile

Consider the photoelectric effect experiment. In one experiment, yellow light shines on a piece of potassium metal. A current is measured, meaning electrons are ejected from the potassium metal. What would happen if the intensity of the yellow light increased?

more electrons would be ejected because increasing the intensity increases the number of photons

Does one molecule of water have a boiling point?

no because the boiling point is the temperature at which the particles change from liquid to gas. If there is only one particle the words liquid and gas (and solid for that matter) are meaningless

isolated system

no transfer of matter or energy (an insulated closed container-hard to do) -soup in an isolated container

does one molecule of water have a boiling point?

no, because the boiling point is the temperature at which the particles change from liquid to gas. If there is only one particle the words are liquid and gas (and solid for that matter) are meaningless

What kind of reaction is this? 4¹H→⁴He+2+₁e

nuclear fusion -e for energy 4 small hydrogen atoms make 1 large He atom

How to calculate thermal energy changes

q=m x c x ∆T =mass(specific heat)(temperature change)

The internuclear distance between two neon atoms compared to the internuclear distance between two krypton atoms where both systems are the most stable is..

smaller because neon has a smaller electron cloud

The boiling point of neon is -246°C and the melting point of neon is -249°C. What state is neon at -260°C?

solid

What is the driving force for bond formation?

the attraction between electrons of one atom and the protons of the other

At what point on the curve are the atoms most stable?

the curve represents the potential energy changes as the distance changes as the distance between two hydrogen atoms changes. Y, because the attractive and repulsive forces are balanced

What is the cause of the attractive force between the two He atoms?

the electron clouds of the He atoms may fluctuate randomly causing a transient dipole that induces a dipole in other atoms which causes them to attract each other.

Consider a system where two helium atoms are approaching from a distance. Two atoms approach and get close enough so that their electron clouds overlap. Why does the potential energy increase?

the electron clouds repel each other

what causes the formation of covalent bonds between atoms?

the electrons on one atom are attracted to the protons on another atom

A calculator on your desk will not move because..

the electrostatic force is equal to the force of gravity

ioniozation energy

the minimum amount of energy required to remove a valence electron

In an isolated system, when two atoms collide...

the total potential energy of the system will not change

What is the best explanation for a pattern such as those obtained when X-Rays are diffracted by crystals?

the waves of electromagnetic radiation arrive in-phase and out of phase at the detector

If the mp/bp is higher then...

there is a stronger interaction present

closed system

transfer energy but not matter (a closed container) -milk carton

molecules that are elements

two or more of the same atom

double slit experiment

waves crisscross & create light on the screen and where they cancel out if where there is darkness

Consider a system where two helium atoms are approaching from a distance. The distance between the two helium atoms where the system would be the most stable is:

where the potential energy is at a minimum

destructive interference

where the two waves are out of phase and cancel out which creates darkness

constructive interference

where two waves in a phase intensifies the light

What is the wavelength of an electron travelling at 5.01 x 10⁵ m/s? The mass of an electron is 9.1 x 10⁻³¹ kg.

λ=h/mv λ=6.626x10⁻³⁴/5.01x10⁵(9.1x10⁻³¹) =1.45x10⁻⁹m


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