Bonding
Draw the Lewis structure for CO2 and state its molecular geometry; explain whether CO2 is polar or nonpolar and why.
CO2: O=C=O linear; nonpolar because bond dipoles cancel.
List the three main types of intermolecular forces from weakest to strongest.
London dispersion < dipole–dipole < hydrogen bonding.
If a gas at 2.00 L at 300 K is heated to 450 K at constant pressure, what is the new volume? (Show work.)
3.0 L
Also known as the slow step in a reaction.
The rate limiting step.
The atomic radius of Ca will increase, decrease, or remain the same when it becomes Ca2+ ion. Justify your answer.
Explain metallic bonding and name two physical properties that arise from metallic bonding.
Metallic bonding: delocalized electrons; properties: conductivity, malleability, ductility.
Predict which of two compounds (e.g., CH4 vs. H2O) will have the higher boiling point and explain why in terms of intermolecular forces.
H2O has higher boiling point due to hydrogen bonding; CH4 only dispersion.
What are the two conditions for an ideal gas.
High temperature and low pressure
Order of the reaction is the plot of the reciprocal of the concentration versus time is linear.
2nd order
Used to calculate the force of two particles as it relates to distance and charge.
Coulomb's Law
Predict the molecular geometry and approximate bond angles for BF3 using VSEPR theory.
BF3: trigonal planar geometry, bond angles 120o.
For a homologous series of alkanes (ex: C3H8, C4H10, C5H12, etc.), explain why boiling point increases with molar mass. Include a brief discussion of surface area and intermolecular forces.
Larger alkanes have greater surface area and more electrons, increasing London dispersion forces and thus higher boiling points.
A sample contains 0.500 mol of an ideal gas at 1.50 atm and 298 K. Calculate its volume in liters. (Show work and include units.)
8.15 L
A reaction follows first-order kinetics with a rate constant k=0.023 s−1. What is the half-life? (Show work.)
30.1 sec
Ca(NO3)2 + Na2CO3 --> CaCO3 + NaNO3.
Write the balanced net ionic equation.
Ca2+ + CO32- --> CaCO3
Draw the Lewis structure for SO2 including any lone pairs; predict its molecular geometry and indicate whether resonance is present.
SO2: resonance structures with one double and one single S–O and a lone pair on S or represented with formal charges; electron-domain geometry: trigonal planar (with one lone pair on S) → molecular shape: bent; resonance present.
Given two substances of similar molar mass, one polar and one nonpolar, explain which will have the higher vapor pressure at the same temperature and why.
Polar compound will have lower vapor pressure (stronger IMFs) than nonpolar at same molar mass.
Calculate the total pressure when three gases in a container exert partial pressures of 0.250 atm, 0.400 atm, and 0.150 atm.
0.800 atm
Explain how a catalyst increases the rate of a reaction in terms of activation energy and reaction pathway.
A catalyst provides a lower-energy pathway (alternative mechanism) with lower activation energy and more favorable transition states, increasing rate without being consumed.
Write the full electron configuration for Zinc.
1s22s22p63s23p64s23d10
Determine the formal charges for each atom in the resonance structure of the nitrate ion, NO3−, and identify the most significant resonance contributor.
In NO3−, each resonance structure places a double bond to one O and single bonds to others; formal charges give nitrogen typically +1, double-bonded O = 0, single-bonded O = -1; best resonance contributors have negative charge delocalized on oxygens (all equivalent).
Describe how branching in hydrocarbons affects boiling point, and explain the role dispersion forces in this trend.
More branching → lower boiling point because less surface contact → weaker dispersion forces.
Which gas molecule would deviate more for an ideal gas? Explain why? Oxygen (O2) or Hydrogen sulfide (H2S)
H2S because it is a polar molecule which will have a greater intermolecular attraction than the nonpolar oxygen molecule.
For the elementary reaction 2A+B→C propose a rate law consistent with an elementary step and identify the molecularity.
For an elementary step 2A+B→C molecularity is termolecular; rate law for an elementary step: rate=k[A]2[B].