DAT Gen Chem Questions
n²= total orbitals in a shell, where n= shell#
What is the formula to get the total orbitals in a shell?
IONIC BONDING (M/NM) 1. Crystalline structure 2. High BP and MP 3. Conductive in liquid 4. Is usually called a "salt"
List 4 properties of Ionic solids.
a) 6hrs if 87.5% has decayed in 18 hours, then after 18 hours 12.5 is left (100 - 87.5 = 12.5), 100 -> 50 -> 25 -> 12.5 -> 6.25 this means 3 half lives have passed, thus 18 hours divided by 3 half lives gives you the half life of the compound which is 6 hours.
After 18hrs 87.5% of a sample of a radioactive nuclide has decayed. What is its half-life? a) 6hrs b) 54hrs c) 9hrs d) 36 hrs
b) 0.25 cal/g°C you must use the equation q=mCΔT since temperature is changing, thus you are using the equation for heat for when a phase change is not occurring (since during a phase change T is constant). since the metal is losing heat and the water is gaining heat (metal was 50°C --> 10°C, and water was 0°C --> 10°C) you set up the equation qwater = -qmetal (50g)(1cal/g°C)(10°C-0°C) = -[(50g)(x)(10°C-50°C)] 500=X(2000) X=1/4 =.25
After a 50g piece of an unknown metal at 50°C is added to 50g of H2O(l) at 0°C, the mixture reaches thermal equilibrium at 10°C. What is the specific heat of the metal? (specific heat of water is 1cal/g°C) a) 5 cal/g°C b) 0.25 cal/g°C c) 0.5 cal/g°C d) 0.2 cal/g°C
METALLIC BONDING (M/M) 1. luster (shiny) 2. ductile (ability to be drawn into wires) 3. malleable (ability to be pounded into sheets) 4. conductive
List 4 properties of Metallic Bonding
Atomic radius increases as you go to the LEFT and DOWN the periodic table
Atomic radius increases as you go in what two directions on the periodic table?
1. H (2) 2. Be (4) 3. B (6) 4. Al (6) 5. 3rd row and lower elements can exceed octet rule
List 5 exceptions to the Octet Rule
BF₃ = trigonal planar (120 degrees)
BF₃ has what sort of molecular geometry? and what are the angles it creates?
Electron Affinity = the change in energy caused by the acceptance of an electron (exothermic energy, the more energy released the more exothermic, the more negative the electron affinity value)
Define Electron Affinity.
Electronegativity = the capacity of an atom in a covalent bond to hoard the electrons shared between the two atoms in the covalent bond
Define Electronegativity.
Ionization Energy = the energy required to pull an electron off an atom
Define Ionization Energy.
a) when going through a phase change (TEMP IS CONSTANT): q=nΔHfus or nΔHvap (where n = # of moles) b) when NOT going through a phase change (TEMP IS CHANGING): q=mCΔT
Describe the equation you use to calculate heat (q) when: a) you are going through a phase change b) you are NOT going through a phase change
Au, Ag, Cu, Mo, Cr all of these are more stable with a half filled or filled d orbital and borrow an electron to make that happen from the s orbital above it
List the 5 transition metal exceptions for electron configuration
a) The N/Z ratio should be equal to one
For Elements below atomic number 20 the N/Z ratio should be? a) The N/Z ratio should be equal to one b) The N/Z ratio should be less than one c) The N/Z ratio should be greater than one d) None of the above are correct
d) None of these if ΔH<0 = -ΔH= exothermic if ΔS>0 = +ΔS = increased entropy Deposition: solid<---gas (exothermic and decreased entropy) Sublimation:solid -->gas (endothermic and increased entropy) Fusion: solid -->liquid (endothermic and increased entropy)
For which of the following phase changes is ΔH<0 and ΔS>0? a) Deposition b) Sublimation c) Fusion d) None of these
b) Sublimation H>0 = endothermic S>0 = increased entropy Deposition = solid <--gas (exothermic and decreased entropy since going from gas to solid state) Sublimation = solid --> gas (endothermic and increased entropy [or disorder] since going from solid to gas state) Freezing = solid <--liquid (endothermic and decreased entropy [or disorder] since going from liquid to a solid state which is more ordered) Condensation = liquid <--gas (exothermic, and decreased entropy [or disorder] since going from liquid to a solid state which is more ordered)
For which of the following phase changes is ΔH>0 and ΔS>0? a) Deposition b) Sublimation c) Freezing d) Condensation
H20 = bent
H2O has what sort of molecular geometry?
in order of least penetrating power to most Royal (Radio wave) Men (Microwave) Invented (Infrared) Very (Visible) Unique (UV) Xray (X ray) Gadgets (Gamma)
List the different radiations in order of least penetrating power to most. include the mnemonic
a) Matter and Energy are related to each other because of the equation E=MC² Matter and Energy are the same, except they are in two different forms.
How are mass (matter) and energy related or not related? a) Matter and Energy are related to each other because of the equation E=MC² Matter and Energy are the same, except they are in two different forms. b) Matter and Energy are not related because they have no relative comparisons found in nature c) Matter and Energy are not related to each other because Energy is intangible and Matter is what makes up all inanimate and animate substances d) Matter and Energy are related because of the equation PV = nRT. Matter and Energy are the same, except they react different depending on temperature and pressure
a) 2 Xe = 8 valence F4 = 7 x 4 = 28 valence Total valence = 36 electrons Xe is the central atom, bond it with the 4 F's and subtract 8 from the total of 36 electrons for the bonds you just made to the central atom which leaves you 28 electrons total. Now put 6 electrons around each F to fulfill its octet rule, which makes you subtract 24 from the 28 electrons left, this leaves you 4 electrons, which you put as 2 lone pairs on the Xe.
How many lone pairs of electrons are around the Xe atom in XeF4? a) 2 b) 1 c) 3
b) 2 I = 7 valence Br = 3 x 7 = 21 valence Total: 28 electrons I is the central atom, after you draw 3 Br's coming off of it, you subtract 6 electrons from the 28 electron total for the bonds you just made. Now you fulfill Br's octet rule and give it 6 electrons for each Br, which brings your total to 18 electrons that you subtract from the remaining 22 electrons, which leaves you 4 electrons to put on the I. This equates to 2 lone pairs.
How many lone pairs of electrons are on the central atom of IBr3? a) 3 b) 2 c) 4 d) 1
c) 9 The formula for total orbitals in a shell is n²= total orbitals in a shell, where n= shell#
How many orbitals does the 3rd shell (n = 3) of an atom contain? a) 3 b) 4 c) 9 d) 18
a) 3470cal q = mCΔT q = (50g)(1cal/g°C)(79.4°C - 10°C ) = 3470cal
How much heat is required to raise 50g of H20 from 10°C to 79.4°C (specific heat of water = 1cal/g°C) a) 3470cal b) 694cal c) 6940cal d) 13880cal
List the ranges of each of the quantum numbers below: a) n = [1...infinity] b) l: [0....(n-1)] or if specified [s=0, p=1, d=2, f=3] c) ml [-L...0...+L] d) ms [-1/2 or +1/2]
List the ranges of each of the quantum numbers below: a) n b) l c) ml d) ms
If the d orbital in a shell is filled then you must get the valence electrons from the s or p orbitals in the shell above the filled d orbital [ie: Br has 7 valence electrons from the 4s and 4p orbitals since its 3d orbital is filled [Ar]4s^2 3d^10 4p^5]
If the d orbital in a shell is filled then where must you get the valence electrons from?
c) BC
In the figure above, which segment corresponds to the conditions where the solid and liquid phases are in equilibrium together? a) BD b) AB c) BC d) None of the above
c) D fusion = solid --> liquid
In the figure, which arrow corresponds to fusion? a) C b) F c) D d) E
a) D critical point is where beyond this point it is called a super critical fluid, where it is not really a gas and not really a liquid
In the figure, which point refers to the critical point? a) D b) B c) C d) A
c) B triple point = point in phase diagram where all 3 phases are in equilibrium with each other.
In the figure, which point refers to the triple point? and describe what it is. a) D b) C c) B d) A
COVALENT BONDING (NM/NM) 1. Network Covalent Bonding (SiO2 - quartz ; Cdiamond) high MP and BP 2. Molecular (Covalent Bonding) low MP and BP
List 2 types of covalent solids that exists.
in isoelectronic ions, the most positive of an isoelectronic series (the one with the most protons) is the smallest in size, while the most negative of the isoelectronic series (the one with the most electrons) is the biggest in size, thus: from smallest to largest: Ca+2, K+, Ar, Cl-, S2-
List these isoelectronic ions in order from smallest to largest atomic radius: S2-, Cl-, Ar, K+, Ca+2
In order of heaviest to lightest: 1) Alpha particle (2 amu) 2) neutron/proton (~1amu) 3) beta particle/electron (<1 amu)
List these items in order of heaviest to lightest: alpha particle, beta particle/electron, neutron, proton
Metals typically form cations whereas non-metals typically form anions
Metals typically form cations/anions whereas non-metals typically form cations/anions.
NH₃ = trigonal pyramidal
NH₃ has what sort of molecular geometry?
NH₄ = tetrahedral (109.5 degrees)
NH₄ has what sort of molecular geometry? and what are the angles it creates?
a) fusion: solid --> liquid (endothermic; +ΔH, +ΔS) b) vaporization: liquid --> gas (endothermic, +ΔH, +ΔS) c) condensation: liquid <--gas (exothermic, -ΔH, -ΔS) d) sublimation: solid --> gas (endothermic, +ΔH, +ΔS) e) crystallization: solid <--liquid (exothermic, -ΔH, -ΔS) f) deposition: solid <---gas (exothermic, -ΔH, -ΔS)
Of the list below describe what phase changes are occurring and whether they are exothermic or endothermic and what sort of entropy it has: a) fusion b) vaporization c) condensation d) sublimation e) crystallization f) deposition
PCl₅ = trigonal bipyramidal (90 degrees, 120 degrees, 180 degrees)
PCl₅ has what sort of molecular geometry? and what are the angles it creates?
P, Si, Cl, S (ranked from lowest to highest) Electron affinity increases from Left to Right, except for the exceptions which are the atoms with a full or half filled subshell such as P which is half filled, which are happy the way they are since they are stable, thus the stable atoms will not give off a lot of exothermic energy when they gain an electron since they are happy the way they are originally. Also the vertical "trend" although there is no vertical trend is that the 2nd row (Cl) has a higher EA than the 1st, or 3rd and 4th rows.
Rank Si, P, Cl and S from lowest to highest Electron Affinity.
SF₆ = octahedral (90 degrees)
SF₆ has what sort of molecular geometry? and what are the angles it creates?
a) 1/32 2.5 x 5 = 12.5 which means 5 half lives have passed after 12.5 hours since 1 half life is 2.5 hours. Thus 1 -> 1/2 -> 1/4 -> 1/8 -> 1/16 -> 1/32 1/32 remains after 5 half lives.
The half-life of a radioactive nuclide is 2.5hrs. What fraction of a sample of this nuclide would remain after 12.5 hrs? a) 1/32 b) 1/16 c) 1/64 d) 1/8
the length of a wavelength corresponds inversely to the amount of energy and frequency (ie: a high energy emission corresponds to short wavelength)
The length of a wavelength corresponds directly/inversely to the amount of energy and frequency
1) F-H or 2) O-H or 3) N-H
What are 3 bonds that NEED to be present if H bonding is to occur?
d) 90° Xe has 2 lone pairs and 4 bonds to F's, which means that this is a octahedral structure and therefore has only 90 degree bond angles.
What are the bond angles in XeF4? a) 60° b) 120° c) 109.5° d) 90°
liquid --> gas = VAPORIZATION
What do you call it when liquid --> gas?
solid <---liquid = CRYSTALLIZATION
What do you call it when solid <---liquid?
liquid <--gas = CONDENSATION
What do you call it when liquid <---gas?
solid --> gas = SUBLIMATION
What do you call it when solid --> gas?
solid <---gas = DEPOSITION
What do you call it when solid <---gas ?
solid ---> liquid = FUSION
What do you call it when a solid ---> liquid?
Coordinate Covalent Bond is a covalent bond in which both of the shared electrons come from the same atom. (Lewis Base donates to Lewis Acid)
What is a Coordinate Covalent Bond?
b) A high-energy photon of light (with no mass)
What is a Gamma Ray? a) A particle from the lowest part of the electromagnetic spectrum b) A high-energy photon of light c) A high-density nucleus particle d) The heaviest form of radioactive decay in terms of AMU (mass unit) transfer
a) A positively charged electron with the same mass and a spin of 1/2
What is a positron? a) A positively charged electron with the same mass and a spin of 1/2 b) A positron is a proton that is positively charged within the nucleus of an atom c) A positron is the result of electrostatic repulsion between different subatomic particles d) A positron is the opposite of a Neutron
f) A & D Strong Nuclear Force and Nuclear Binding Energy is holding the nucleus together. The Strong Nuclear Force holds the protons and neutrons together in the nucleus. The impact of this force is only seen when protons and neutrons are small distances apart. This distance is something observed inside the nucleus where the objects are tightly packed together. The strong force therefore overpowers the electrostatic repulsion force that you would typically observe from protons that are farther distances apart. Nuclear Binding Energy is simply the quantifiable energy required to split a nucleus.
What is responsible for holding the Nucleus together? a) Strong Nuclear Force b) Electrostatic Repulsion c) Protons d) Nuclear Binding Energy e) B & C f) A & D
2(n²) = total electrons that can exist in a shell, where n = shell #
What is the formula for the total electrons that can exist in a shell?
a) sp2 double and triple bonds count as one "thing" when counting for hybridization so you have 3 "things" around the central S, one bond from the O on the left of the S, the lone pair on top of the S, and the double bond on the right of the S, thus sp2.
What is the hybridization of the central atom in SO2? a) sp2 b) sp c) dsp3 d) sp3
d) sp3d Xe has 3 lone pairs on it as well as the 2 bonds to the F's, thus it has 5 "things" around it, the only thing with 5 things is sp3d (sp3 = 4 things + the d = 5)
What is the hybridization of the central atom in XeF2? a) sp b) sp2 c) sp3 d) sp3d
c) sp3d2 Xe has 2 lone pairs, as well as the 4 bonds it has to the F's, thus it has 6 "things" around the central atom. sp3 = 4 things + d2 = 6 things total.
What is the hybridization of the central atom in XeF4? a) sp3 b) dsp3 c) sp3d2 d) sp2
d) linear H has a single bond to the central C which has a triple bond to the N, and the N has a lone pair. triple bonds are always linear.
What is the molecular geometry of HCN? a) tetrahedral b) bent c) trigonal planar d) linear
a) See-saw See-saw = 1 lone pair + 4 bonds
What is the molecular geometry of SF4? a) See-saw b) Tetrahedral c) Square pyramidal d) Trigonal Planar
CONDENSATION = liquid <--gas
When CONDENSATION is occurring, what state does it start at and what state does it end in?
CRYSTALLIZATION = solid <--liquid
When CRYSTALLIZATION is occurring, what state does it start at and what state does it end in?
DEPOSITION = solid <--gas
When DEPOSITION is occurring, what state does it start at and what state does it end in?
FUSION = solid --> liquid
When FUSION is occurring, what state does it start at and what state does it end in?
SUBLIMATION = solid --> gas
When SUBLIMATION is occurring, what state does it start at and what state does it end in?
VAPORIZATION = liquid --> gas
When VAPORIZATION is occurring, what state does it start at and what state does it end in?
When a phase change is occurring the temperature: a) remains constant temperature remains constant (look at calorimetry graph) since even though heat is being added, the temperature does not increase during a phase change, since the heat energy is being put toward making the phase change happen by breaking bonds.
When a phase change is occurring the temperature: a) remains constant b) changes by going up or down c) cannot be determined
a) alpha decay : mass reduction (only nuclear decay that can reduce mass, usually happens frequently to the heavier elements where z>83) b) beta decay: when N/Z ratio is too high (high/too many neutrons, low/not enough protons) [n-->p] c) positron emission: when N/Z ratio is too low (low/not enough neutrons, high/too many protons) [p-->n] d) electron capture [p-->n]
When are the spontaneous routes of decay utilized below? a) alpha decay b) beta decay c) positron emission d) electron capture
Fe-56
Which element has the most stable nucleus/highest nuclear binding energy per nucleon?
c) Fe-¹ This is heaviest because it has more electrons. As we have learned, that although electrons are NEARLY massless, they still have some mass
Which of the following atoms are heaviest: a) Fe+² b) They all weigh the same c) Fe-¹ d) Fe
The compounds with the highest IM forces will have the highest BP. Choice C although polar is not as strong as the hydrogen bonding seen in the other 3 choices. (Ranking of bonds go like: ionic or network covalent >> hydrogen bonding > dipole-dipole > London dispersion/Van Der Waals forces.) Choice D is the correct answer because choice D is the only one that has the greatest SA, as well as weight and size. Thus its has the greatest IM forces.
Which of the following compounds has the highest boiling point? a) CH3OH b) CH3CH2OH c) CH3CH2CH2F d) CH3CH2CH2OH
c) He Vapor pressure is the only condition that is inversely related to high IM forces. This is because the stronger the force of two molecules that are bound to each other, the less likely it will be to turn into a gas. Therefore the molecule with the lowest IM forces (London Dispersion/Van Der Waals for non-polar compounds) will have the highest vapor pressure, but since all the choices are noble gases which are all non-polar they all have London Disperson/Van Der Waals forces, size is the ultimate decider in this answer. Since He is the smallest in size, it has the smallest SA, which means it has the lowest IM forces (since increased SA = increased IM forces), and thus the highest vapor pressure.
Which of the following compounds has the highest vapor pressure? a) Ar b) Ne c) He d) Kr
a) n=2 to n=3 Since this is an ABSORPTION, you must go from low energy level to a higher energy level (emission = high energy level to lower energy level) the lower the energy level you start at to a higher energy level, the greater the energy absorption is. The wavelength is inversely proportional to energy absorption and emission, thus the lowest energy absorption is by n=2 to n=3 which would give you the longest wavelength. Choice D is an emission and choice B is the highest energy absorption, and after that would be choice C as the second highest energy absorption.
Which of the following electronic transitions in the hydrogen atom would involve an absorption a photon of the longest wavelength? a) n=2 to n=3 b) n=1 to n=4 c) n=1 to n=3 d) n=4 to n=1
d) n=5 to n=1 wavelength is inversely proportional to energy emitted or absorbed. Thus the photon that has the greatest energy emission which is choice D would have the shortest wavelength.
Which of the following electronic transitions in the hydrogen atom would involve an emission of a photon of the shortest wavelength? a) n=1 to n=5 b) n=3 to n=1 c) n=3 to n=2 d) n=5 to n=1
Choices A, B and D are metals and therefore cations which have a smaller atomic radius than its neutral counterpart since it is losing an electron in its valence shell which allows the proton to pull the electrons even closer to the nucleus. Choice C is the only nonmetal and is a anion, which have bigger atomic radius than its neutral counterpart since it is gaining an electron in its valence shell to get the negative charge.
Which of the following has an ionic radius that is larger than its atomic radius? a) Mg b) K c) Cl d) Ag
b) CHCl3 All 4 molecules are nonpolar and have Van Der Waals/London Dispersion Forces, thus, the deciding factor is size or more importantly, weight. CHCl3 has the heaviest molecular weight out of all the choices since it has the most Chlorines which is the heaviest atom. Thus since it is the heaviest, it will have the highest IM forces.
Which of the following has the greatest intermolecular forces? a) CH2Cl2 b) CHCl3 c) CH4 d) CH3Cl
b) H2O Choice b has H bonding, which is the strongest out of all the choices. All the other choices have dipole dipole and van der waals/london dispersion forces
Which of the following has the greatest intermolecular forces? a) H2S b) H2O c) H2Te d) H2Se
c) H2Te Te is the biggest in size compared to S or Se, thus increased size = increased IM forces.
Which of the following has the greatest intermolecular forces? a) H2S b) H2Se c) H2Te d) Cannot be determined without more information
d) C EA ranked from lowest to highest: N, Be, C, B This is because EA is the amount of exothermic (neg) energy given off when an atom gains an electron. The happier the atom is to take on the electron the bigger the amount of energy it gives off. N is a half filled subshell so it wants to stay the way it is and not gain or lose any electrons, thus it has a lower EA than C the element before it.
Which of the following has the highest (most negative) electron affinity? a) N b) Be c) B d) C
these elements ranked from lowest to highest electron affinity: N, C , O , F (N is an exception since it has a half filled subshell and will not give off a lot of energy if it gains an electron since it wants to stay the way it is, thus it has a lower EA than C, F has the highest EA since it wants to be a noble gas and will give off a lot of energy when it gains an electron) EA increases from LEFT to RIGHT and the 2nd row (Cl) has the highest EA compared to row 1 and row 3 and 4.
Which of the following has the highest (most negative) electron affinity? a) O b) F c) N d) C
b) NaOH Choice B is the answer since it has the strongest IM forces out of all the choices and thus the highest BP. Choice B is ionic bonding, whereas the other 3 choices are H bonding. (Ranking of bonds go like: ionic or network covalent >> hydrogen bonding > dipole-dipole > London dispersion/Van Der Waals forces.)
Which of the following has the highest boiling point? a) CH3CH2OH b) NaOH c) H2O d) HOCH2CH2OH
c) NaCl Choice C is the answer since it has the strongest IM forces out of all the choices and thus the highest BP. Choice C is ionic bonding, whereas choice A, B and E are H bonding. Choice D is nonpolar since it is a noble gas thus is only London Disperson/Van Der Waals forces and will have the lowest BP out of them all (Ranking of bonds go like: ionic or network covalent >> hydrogen bonding > dipole-dipole > London dispersion/Van Der Waals forces.)
Which of the following has the highest boiling point? a) HOCH2CH2OH b) H2O c) NaCl d) Ar e) CH3OCH3
d) N IE increases as you go UP and to the RIGHT. Be careful of minding the exceptions for IE, which are for the elements one above a half filled or fully filled subshell. These elements will have a lower IE than the element before it since they want to lose an electron to become the more stable configuration of half filled or fully filled subshell (with the exception of noble gases which have the highest IE)
Which of the following has the highest first ionization energy? a) Cs b) C c) B d) N
c) N The atoms ranked from lowest to highest IE: B, C, O, N. This is because O is 1 electron away from having a filled subshell if it gets an electron taken away so it will have a lower IE (energy required to take an electron away from an element) than N to its left which has a half-filled subshell. Similarly, Be would have a higher IE than B since B is 1 electron away from having a filled subshell like Be if it loses an electron.
Which of the following has the highest first ionization energy? a) O b) C c) N d) B
a) Ge atomic radius increases as you go DOWN and to the LEFT
Which of the following has the largest atomic radius? a) Ge b) As c) O d) S
d) Te Atomic radius increases as you go LEFT and DOWN
Which of the following has the largest atomic radius? a) P b) F c) S d) Te
b) I- atomic radius increases DOWN and to the LEFT. if it is a anion, the size increases from its neutral state since electrons are being added to the outer valence shell.
Which of the following has the largest ionic radius? a) F- b) I- c) Cl- d) Br-
a) [4,0,0,-1/2] Br electron configuration: [Ar]4s²3d¹⁰4p⁵ valence electrons are from 4s² and 4p⁵, thus n = 4 so choice B and choice D are eliminated. l for s = 0, p = 1, d =2, f = 3. So l can only be 0 or 1. ml has to be [-L ....+L] so has to be answer A since choice C has -2 has the ml value.
Which of the following is a possible set of quantum numbers [n,l,ml,ms] for a valence electron in bromine? a) [4,0,0,-1/2] b) [3,1,1,+1/2] c) [4,1,-2,+1/2] d) [3,2,-1,-1/2]
d) gold-196 To determine radioactivity likelihood you use two methods: 1st method: see if there is both an odd number of neutrons and protons 2nd method: if above method cannot be applied then compare N/Z ratio (aka neutron:proton ratio) which should be 1:1 for nonradioactive elements with Z <20 (Z is the atomic number aka proton number of an element) Carbon-12 has 6 protons (Z=6) and 6 neutrons so its not radioactive Oxygen-16 has 8 protons (Z=8) and 8 neutrons so it is not radioactive Magnesium-24 has 12 protons (Z=12) and 12 neutrons so it is not radioactive Gold-196 has 79 protons (Z=79) and 117 neutrons so it is radioactive since it has both an odd number of protons and neutrons
Which of the following is most likely to be radioactive? a) carbon-12 b) oxygen-16 c) magnesium-24 d) gold-196
c) uranium-235 alpha decay usually happens in elements that are heavy (Z>83) for mass reduction. Uranium-235 is the only element listed that has Z>83
Which of the following is most likely to decay by alpha emission? a) sodium -23 b) carbon-14 c) uranium-235 d) helium-4
c) carbon-14
Which of the following is most likely to decay by beta emission? a) calcium-40 b) oxygen-16 c) carbon-14 d) nitrogen-14
The answer is the second to last one. C = 4 valence O = 6 valence H2 = 1x2 = 2 valence total: 12 valence C is the least electronegative atom so it is the central atom, and once you draw the O and 2 H's coming off of it you subtract 6 from the total of 12 valence electrons. With the remaining 6 electrons you put it around the O, however you see that the central C does not fulfill the octet rule, so you donate a lone pair from the O to the C to make a double bond. Once that is done you see that there is no formal charges on the atom and that this is the correct form.
Which of the following is the correct Lewis structure for H2CO?
c) C-O O is the most electronegative element out of the other thus it will have the most polar bond.
Which of the following is the most polar bond? a) C-Br b) C-S c) C-O d) C-N
e) NO3- First when looking for molecules with 3 resonance structures we look for molecules that have 3 atoms around the central atom that can participate in resonance (H is not an atom that can participate in resonance even if it is attached to the central atom, thus choice A is eliminated) That leaves choice B and choice E has the only options. Choice B when drawn out cannot give you resonance since it is a trigonal planar molecule. Thus E is the answer.
Which of the following molecules/ions is represented by 3 resonance structures? a) HClO2 b) PBr3 c) O3 d) CO e) NO3-
Sublimation = solid --> gas (endothermic) Fusion = solid --> liquid (endothermic) Vaporization = liquid --> gas (endothermic) Condensation = liquid <--gas (exothermic)
Which of the following processes is exothermic? a) Sublimation b) Fusion c) Vaporization d) Condensation
d) Both positron emission and electron capture shown is electron capture.
Which of the following result in the conversion of a proton into a neutron? a) Positron emission b) Beta decay c) Electron capture d) Both positron emission and electron capture
c) Na Na is the only one with 1 valence electron. All the other elements have 2 valence electrons at least, thus Na would have the highest 2nd IE (energy it takes to take away an electron from an atom)
Which of the following would have the highest 2nd ionization energy? a) Be b) C c) Na d) Mg
c) Be Be is the only one with 2 electrons only in its valence, so the 3rd ionization energy for it would be the highest. All the other elements have more than 2 electrons in its valence electrons.
Which of the following would have the highest 3rd ionization energy? a) B b) N c) Be d) C
The last one is the answer. Since N20 has no formal charges on it the charges on the answer selections should equal 0. The First answer choice can be eliminated because it gives the molecule a formal charge of -2, The second answer choice can be eliminated because it gives the molecule a formal charge of -1, The third choice should be eliminated because N has a charge of -2 and both Oxygens have + charges, the rule is that the more electronegative atom should hold the negative charge, and O is more electronegative than N. Also another rule is that the least electronegative atom should be the central atom. When drawing out this lewis structure, we first calculate the total valence electrons which is N2 = 5 x 2 and O = 6 which gives us a total of 16 total valence electrons. Since N is the least electronegative atom we put it at the center like so: N-N-O (16-4 for the bonds we just made which gives us a new total of 12) Then we put 6 electrons around both the N and the O on either end. However this leaves the central N not fulfilling the octet rule. To find out which atom the N or O on either end donates their lone pairs to the central N, try it all 3 ways. we see that if the N on the left donates 2 lone pairs to the central atom then the N on the end will have 0 charge, the central N will have a + charge and the O on the end will have a - charge. This is the correct form since the negative charge is on the most electroneg atom (O) and the positive charge is on the least electroneg. atom (N), If N and O from both ends both donate 1 lone pair to the central N, then you end up with a - charge on the N on the end and a + charge on the central N with no charge on the O. As stated before, the ideal resonance form is one where the - charge is on the most electronegative atom so this form is not preferred. The final option is if O on the end donates 2 lone pairs to the central N which gives the N on the end a -2 charge, the central N a + charge and a + charge on the O at the end, this is the most unfavorable form since there are too many charges and the negative charge is also on the N on the end and not the O.
Which one of these is a valid resonance contributer for N2O?
a) +q means that heat was gained by the system b) -q means that heat was lost by the system
a) +q means what? b) -q means what?
a) anions have a BIGGER atomic radius than their corresponding neutral species b) cations have a SMALLER atomic radius than their corresponding neutral species?
a) anions have a bigger/smaller atomic radius than their corresponding neutral species? b) cations have a bigger/smaller atomic radius than their corresponding neutral species?