GenChem201 Ch. 4-6 (Exam 2)
Bond order equation (given)
(# bonding electrons - # antibonding electrons)/2
300.0 mL of a 0.400 M solution of NaI is diluted to 700.0 mL. What is the new concentration of the solution?
0.171 M
Determine the amount in grams of KCl that exists in 20.3 g of a solution that contains 1.14 % KCl by mass.
0.231 g KCl
What is the bond order of H₂⁺?
0.5
What volume in L of a 0.724 M NaI solution contains 0.405 mol of NaI?
0.559 L
Greek Prefixes 1-10
1-mono 2-di 3-tri 4-tetra 5-penta 6-hexa 7-hepta 8-octa 9-nona 10-deca
How to determine empirical formula (given % composition)
1. Convert % composition to masses of elements assuming a 100g sample of the compound. 2. Convert element masses to moles by using molar mass. 3. Divide each number of moles by the smallest number of moles. 4. If necessary, multiply by an integer to get a whole number ratio.
How to determine empirical formula (given mass)
1. Convert element mass to moles using molar mass 2. Divide each number of moles by the smallest number of moles. 3. If necessary, multiply by an integer to get a whole number ratio.
Naming Binary Acids (HX)
1. Hydrogen becomes 'hydro' 2. Use '-ic' suffix on second element 3. Add 'acid' ex. HBR (aq) = hydrobromic acid ex. HCl (aq) = hydrochloric acid
Naming Hydrates
1. Name cation 2. Name anion 3. Use greek prefix + 'hydrate' ex. CuSO4 • 5H20 = copper (II) sulfate pentahydrate
Naming a ion with a charged metal
1. Name cation 2. Name anion with '-ide' 3. Add Roman Numeral to cation ex. FeCl2 = iron (II) chloride ex. FeCl3 = iron (III) chloride
Naming monatomic ions
1. Name cation 2. Name anion with '-ide' suffix ex. NaCl = Sodium Chloride ex. Al2O3 = Aluminum Oxide
What is the mass % of ethylene glycol in a 2.37 M solution of ethylene glycol (MM = 62.07 g/mol) in water? The density of the solution is 1.07 g/mL.
13.7 %m
What is the mass % of propylene glycol in a 1.85 M solution of propylene glycol (MM = 76.09 g/mol) in water? The density of the solution is 1.03 g/mL.
13.7 %m
A compound has the empirical formula CH2O (mass = 30g) and a molecular mass of 180g. What is the molecular formula of the compound?
180g/mol ----------- = 6 (CH20) = C6H12O6 30 g/mol
What is the concentration in %m/v of a 0.481 M aqueous solution of ethanol (MM = 46.07 g/mol)?
2.22%
What is the concentration in %m/v of a 0.345 M aqueous solution of propylene glycol (MM = 76.09 g/mol)?
2.63 %
What is the %v/v of a solution made from 141.1 g of ethylene glycol (density is 1.11 g/mL) in water (density 1.00 g/mL) to form a total volume of 500.0 mL? You may assume the density of ethylene glycol does not change in the solution.
25.4 %
If 50.0 g of CH₃OH (MM = 32.04 g/mol) are added to a 500.0 mL volumetric flask, and water is added to fill the flask, what is the concentration of CH₃OH in the resulting solution?
3.12 M
The density of helium in a balloon is 1.18 g/L. If a balloon holds 2.87 L of He, how many atoms of He are in the balloon?
5.10 × 10²³ atoms
What volume in mL of 0.220 M HBr solution is required to produce 0.0150 moles of HBr?
68.2 mL
An unknown compound containing tellurium and bromine is analyzed and it is determined that 28.53% of the compound by mass is composed of tellurium. What is the mass percent of Br in the compound?
71.47 %
Polar Covalent Bond
A covalent bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive.
Pure Covalent Bond
A covalent bond with perfectly equal sharing of electrons between atoms.
orbital energy diagram
A diagram that shows all of the orbitals and their relative energies. Often includes boxes or spaces to draw electrons, in order to determine the electron configuration.
Anion
A negatively charged ion
Solute
A substance that is dissolved in a solution.
Which of these molecules have delocalized electrons? A) CO₃²⁻ B) CO₂ C) NF₃ D) CH₄
A) CO₃²⁻ Draw the Lewis structure of each molecule and determine which has resonance. Resonance results in alternate ways to distribute electrons but still maintains a valid Lewis Structure. CO₃²⁻ has delocalized electrons.
Rank the following diatomic molecules in order of bond length (from smallest to largest). A) NO⁺ < NO < NO⁻ B) NO⁻ < NO < NO⁺ C) NO < NO⁻ < NO⁺ D) NO⁻ < NO⁺ < NO
A) NO⁺ < NO < NO⁻ NO has 11 electrons in the valence shell. This means that there is an electron in a π∗ antibonding orbital. This species has a bond order of 2.5. When an electron is added, it will also be added to a π∗ orbital decreasing the bond order to 2.0. When an electron is removed, there are no electrons in the antibonding orbitals and the bond order will increase to 3.0. Molecules with higher bond order have shorter bond lengths.
The reason an ionic bond forms can best be described as A) the energy change for electron transfer results in a large gain in stability when the ionic bond forms. B) two atoms need to share electrons in order to fill their valence shells. C) two atoms exist as ions and the ions are attracted to each other. D) the atoms that form cations have low ionization energy and anions have high electron affinity, so the two atoms exchange electrons.
A) the energy change for electron transfer results in a large gain in stability when the ionic bond forms.
A molecule that contains delocalized electrons ________ A) will have at least two resonance structures. B) will have only single bonds in its chemical structure. C) will be any molecule that contains a double bond. D) will be any molecule that contains a π bond.
A) will have at least two resonance structures. A molecule that contains delocalized electrons will have at least two resonance structures because the electrons can either be on one side or the other.
Electron Pair Geometry
Arrangement around a central atom of all regions of electron density (bonds, lone pairs, or unpaired electrons)
What is the electron configuration of K⁺? A) 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶ B) 1s²2s²2p⁶3s²3p⁶ C) 1s²2s²2p⁶3s²3p⁶4s² D) 1s²2s²2p⁶ E) 1s²2s²2p⁶3s²3p⁵
B) 1s²2s²2p⁶3s²3p⁶
Which atomic orbitals from carbon hybridize to form the bonds in CH₄? A) 1s, 2p_x, 2p_y, 2p_z B) 2s, 2p_x, 2p_y, 2p_z C) 3s, 3p_x, 2p_y, 2p_z D) 2s, 2p_x, 2p_y
B) 2s, 2p_x, 2p_y, 2p_z Draw the orbital energy diagram for C to find where its valence electrons are. They are found in 2s, 2p_x, 2p_y, 2p_z
A 12.5 g sample of a hydrate of calcium chloride is found to contain 3.06 g of water. What is the formula of the hydrate? A) CaCl₂･4 H₂O B) CaCl₂･2 H₂O C) CaCl₂･3 H₂O D) 2 CaCl₂･3 H₂O
B) CaCl₂･2 H₂O
Which hybrid orbitals overlap in the C - O bond in CF₂O? A) Csp² - Os B) Csp² - Osp² C) Csp² - Osp³ D) Csp³ - Osp³ E) Csp³ - Osp
B) Csp² - Osp² In the Lewis structure of CF2O both the C and O atoms are sp2s hybridized. The C-O sigma bond is formed between the C−sp2 orbital and the O−sp2 orbital.
If you are given the molarity of a solution, what additional information would you need to find the weight/volume percent (w/v%)? A) No additional information is required B) The molar mass of the solute C) The molar mass of the solvent D) The molar mass of the solute and solvent E) The density of the solution
B) The molar mass of the solute
100.0 mL of a 0.500 M solution of KBr is diluted to 500.0 mL. What is the new concentration of the solution? A) 2.50 M B) 0.500 M C) 0.100 M D) 0.0250 M
C) 0.100 M
Which of the following bonds is a polar covalent bond? A) Li - Cl B) Cl - Cl C) H - Cl D) Li - Li
C) H - Cl Polar bonds occur between two nonmetals and have a difference in electronegativities of the atoms of approximately 0.5-2.0.
The term 'delocalization' refers to A) electrons being shared between two atoms in σ bonds. B) electrons being shared between two atoms in π bonds. C) electrons being shared via π bonds between more than just two atoms. D) electrons being shared via σ bonds between more than two atoms. E) the uncertainty of the exact location of an electron occupying an orbital.
C) electrons being shared via π bonds between more than just two atoms.
Provide the correct nomenclature for Ca(NO₃)₂
Calcium Nitrate
ionic bonding
Chemical bonding that results from the electrical attraction between cations and anions (Metal + Nonmetal)
What is the chemical formula for dichlorine heptoxide?
Cl₂O₇
Which of the following contains the highest number of atoms? A) 1 mole of helium B) 1 mole of carbon C) 1 mole of uranium D) All contain an equal number of atoms E) Not enough info
D) All contain an equal number of atoms One mole of any substance is equal to 6.022 × 10²³ particles of that substance.
Which one of the following bonds has the least ionic character? A) Li - Cl B) Na - Cl C) Ca - Cl D) B - Cl
D) B - Cl A bond between B-Cl would have the least ionic character because it is between two nonmetals.
Which molecule contains sp hybridized orbitals? A) C₂H₆ B) CH₄ C) C₂H₄ D) C₃H₄
D) C₃H₄ In the Lewis structure of C3H4, the central carbon atom is sp-hybridized.
An iron-containing compound is 20.1% Fe, 11.5% S, 63.3% O, and 5.1% H. What is the empirical formula for this compound? A) Fe₃SO₁₉H₂₅ B) Fe₁₅S₉O₅₀H C) FeS₂O₂₂H₂₈ D) FeSO₁₁H₁₄
D) FeSO₁₁H₁₄
A compound containing Na, C, and O is found to have 1.06 mol Na, 0.528 mol C, and 1.59 mol O. What is the empirical formula of the compound? A) NaCO B) Na₂CO C) Na₂CO₂ D) Na₂CO₃
D) Na₂CO₃
Which of the following bonds is the most polar? A) P - S B) C - Cl C) F - F D) Rb - Br E) All bonds have equal polarity.
D) Rb - Br Elements that are located far away from each other on the periodic table have larger electronegativity differences and therefore make more polar bonds. Of all the element pairs listed, Rb and Br are the farthest apart.
Which diatomic molecule has the smallest (lowest) dipole moment? A) F₂ B) O₂ C) N₂ D) H₂ E) All equal
E) All equal
If you are given the molarity of a solution, what additional information would you need to find the weight/weight percent (w/w%)? A) The molar mass of the solute B) The molar mass of the solvent C) The density of the solution D) The molar mass of the solute and the molar mass of the solvent E) The molar mass of the solute and the density of the solution
E) The molar mass of the solute and the density of the solution
What is the chemical formula for krypton dichloride?
KrCl₂
Order of repulsions
LP-LP > LP-BP > BP-BP
Smaller the bond order
Longer the bond length
Metal and Nonmetal Cations
Low ionization energy (lose electrons easily, which forms positive charge)
Molarity equation
M = moles of solute/liters of solution
Dilution equation
M1V1=M2V2 (molarity and volume)
Provide the correct IUPAC name for MnSO₄
Manganese (II) Sulfate
Solution Concentration
Molarity (M) is the amount of solute (in moles) divided by the volume of solution (in liters).
Which orbitals form sigma bonds?
S-S orbital, S-P orbital, P-P orbital
Molecular Geometry
The arrangement of atoms determined by the arrangement of bonding electron pairs and lone pairs around the central atom in a molecule.
pi-bond (π-bond)
The reactive part of a double bond formed above and below the plane of the bonded atoms by sideways overlap of p-orbitals.
Octet Rule
The tendency of main group atoms to form bonds to obtain eight valence electrons
Atomic orbital hybridization
When under the influence of the nucleus of an "incoming" atom, the shapes of the orbitals of central atoms become distorted.
Covalent Bonding
a bond formed when atoms share one or more pairs of electrons
Discrete Molecules
a covalent molecule in which the intermolecular forces are really weak, hence the low melting and boiling points of these molecules.
Sigma bonds
a single covalent bond that is formed when an electron pair is shared by the direct overlap of bonding orbitals
Bond dipole equation
bond dipole strength = (magnitude of S-,S+)(distance)
What do you add to ionic lewis structures
brackets!
Ionic substances are composed of
discrete cations and anions combined in ratios to yield electrically neutral bulk matter
Groups 13~17 will
lose outermost valence shell and "s" and "p" electrons
Group 1 and 2 will
lose outermost valence shell and "s" electrons (to form noble gas configuration which is most stable)
Characteristics of covalent bonding
lower melting points and boiling points, non-conductors
LUMO
lowest unoccupied molecular orbital
Percent composition formula
mass of element/total molar mass x 100 ex. What is the percent of hydrogen in NH3 (MM=17.03)? %H= 1.008 x 3 = 3.024 3.034/17.03 x 100 = 17.76%
What equation determines if the empirical formula is the same as molecular formula?
molecular/molar mass -------------------------- = x formula units to multiply by empirical/formula mass
Solute (n) equation
n (mol/L) = (molarity M)(volume L)
Dipole Moment
net separation of charge in a molecule
Diamagnetic
no unpaired electrons
destructive interference in electrons
results in antibonding
constructive interference in electrons
results in bonding
Bond dipole
separation of electrical charge created when atoms with different electronegativities form a covalent bond
Double Bond
sigma and pi bond
Single Bond
sigma bond
Triple Bond
sigma bond and 2 pi bonds
What is the hybridization of BH3? (3 e- domains)
sp2
What is the hybridization of CH4? (4 e- domains)
sp3
What is the hybridization of XeF5? (7 e- domains)
sp3d3
The higher the bond order the _____ the bond
stronger and shorter
Electronegativity
the ability of an atom to attract electrons when the atom is in a compound
Resonance hybrid structure
the actual structure of a molecule that is intermediate between two or more resonance structures (all possible lewis structures)
Electron Affinity
the energy change that occurs when an electron is acquired/ejected by an atom
Formal charge
the hypothetical charge the atom would have if we could redistribute the electrons in the bonds evenly between the atoms
Bond order
the number of electron pairs between atoms: 1 for a single bond, 2 for a double bond, and 3 for a triple bond
Percent composition
the percent by mass of each element in a compound
Dilution
the process of adding solvent to lower the concentration of solute in a solution
Solvent
the substance in which the solute dissolves
Formula Mass (molar mass)
the sum of the average atomic masses of all atoms represented in its formula ex. NaCl Na x 1 = 22.99 Cl x 1 = 35.45 22.99 + 35.45 = 58.44 amu/g
Transition Metals (Groups 3-12)
valence "s" electrons less stable than "d" electrons
Formal charge equation (given)
valence electrons - nonbonding electrons - 1/2(bonding electrons)
volume percent (v/v)
volume of solute/volume of solution x 100%
What is ideal formal charge
0, or the smallest FC possible exception: it is an ion and has a negative charge, that must be represented on the more electronegative atom (vise versa with positive)
How many moles of HCl are there in 75.0 mL of 0.410 M HCl?
0.0308 mol
What is the concentration in molarity of an aqueous solution which contains 2.95% by mass acetone (MM = 58.08 g/mol)? The density of the solution is 0.971 g/mL.
0.493 M
Roman Numerals 1-5
1: I 2: II 3: III 4: IV 5: V
Calculate the bond order for CO
3 8 - 2 ------- = bond order of 3 2
What is the value of Avogadro's number?
6.022 × 10²³
Provide the correct nomenclature for AlPO₄
Aluminum Phosphate
What is the shape of the 2p orbitals? A) sphere B) dumbbell C) cloverleaf D) raindrop
B) dumbbell
Provide the correct nomenclature for BrCl₃
Bromine Trichloride
What is the mass percentage of O in C₃H₈O₂? A) 21.03% B) 57.94% C) 72.58% D) 42.06%
D) 42.06%
Fill in the blank: A molar mass value is equivalent to any element's ___________. A) density B) temperature C) boiling point D) atomic weight
D) atomic weight
A π bond could be formed from the overlap of which two orbitals? A) two sp² hybrid orbitals B) a 1s and a sp² hybrid orbital C) a sp and a sp² hybrid orbitals D) two unhybridized p orbitals
D) two unhybridized p orbitals Pi (π) bonds are formed by overlapping p orbitals.
Provide the correct nomclature for As₂S₅
Diarsenic Pentasulfide
Describe the change in energy when a bond is broken
Energy is absorbed from surrounding (endothermic)
Describe the change in energy when a bond is formed
Energy is released to the surroundings (exothermic)
mass/volume percent (m/v)
Grams of solute/milliliters of solution X 100%
Nonmetal Anion
High ionization energy (gain electrons easily, which forms negative charge).
Mixture vs Pure substance
Mixtures can be physically separated Pure substances cannot be physically separated (elements and compounds)
homogeneous mixture (solution)
a mixture that is uniform in its properties and composition
VSEPR theory
electrons repel each other, molecules adapt conformations which minimize repulsions by maximizing the distance between regions of electron density
Electronic Structure of Anions
full shell is more stable, tend to fill "s" and "p" orbitals by gaining electrons
Paramagnetic
has unpaired electrons
Characteristics of ionic bonding
high melting and boiling points, dissolves in polar materials, crystal lattice structure, free moving ions, and solids do not conduct
HOMO
highest occupied molecular orbital
What is the number of moles of glucose (C₆H₁₂O₆) in 0.500 L of a 0.40 M solution?
0.20 mol C₆H₁₂O₆.
Empirical formula
a formula with the lowest whole-number ratio of elements in a compound (not necessarily the actual numbers)
polar molecule
a molecule in which one side of the molecule is slightly negative and the opposite side is slightly positive
The chemical formula for the anticoagulant heparin is C₁₂H₁₉NO₂₀S₃. What is the mass in grams of heparin that in 0.0013 moles?
0.80 g
A particular beer is 6.50 % ethanol by volume (C₂H₆O). If a single bottle of beer contains 750.0 mL of beer , what quantity in moles of ethanol (C₂H₆O) are present in the bottle? The density of ethanol is 0.789 g ethanol/mL ethanol .
0.835 mol ethanol.
In sp²-hybridized orbitals, how many p-orbitals remain to form multiple bonds?
1 There are three p-orbitals and one s-orbital in each energy level, but an sp2-hybridized orbital uses more than one of the p-orbitals. This means that sp2 hybridization leaves one p orbital free to pi bond.
Naming polyatomic ions
1. Name cation 2. Name anion ex. KOH = Potassium Hydroxide ex. Na3PO4 = Sodium Phosphate
Naming molecular compounds
1. The element further left and/or towards the bottom of the table goes first (more metallic) 2. Use greek prefixes to specify ratios 3. Use 'ide' suffix on second element ex. CO2 = carbon dioxide ex. N2O4 = dinotrigen tetroxide ex. PF5 = phosphorus pentafloride
Cation
A positively charged ion
Which atom in the C-F bond has a partial positive charge (δ⁺)? A) C B) F C) Both D) Neither
A) C Partial charges are determined by the relative electronegativities of the atoms in a bond; the less electronegative atom, which is C, has a partial positive charge.
What is the molecular formula of a compound with an empirical formula of CH and a molar mass of 78.1 g/mol? A) C₆H B) C₂H₂ C) C₂H₆ D) C₆H₆
D) C₆H₆ The molar mass of CH is 13.02 g. Divide the molar mass of the unknown compound by the molar mass of the empirical formula to find the total number of CH units in the molecular formula. 78.1g/ 13.02g = 6(CH) = C₆H₆