Chapter 7
Rank these from highest to lowest lattice energy:
NaCl, MgCl_2, KBr, CaCl_2
If NaCl has a lattice energy of -600 KJ/n, what could estimate the lattice energy of MgCl_2 as assuming the radii are the same?
MgCl2>CaCl2>NaCl>KBr
-1200 KJ/n
If I wanted to create a n-type semiconductor for Si and a p-type semiconductor for Ge, what elements could I use?
(There is more than one correct answer)
n-type Si: group 15
p-type Ge: group 13
A system absorbs 85 kJ of heat from the surroundings and does 32 kJ of work on the surroundings.
a) Calculate the change in internal energy ΔE.
b) State whether the internal energy of the system increases or decreases.
a.) +53 KJ
b.) Increases
How many resonance structures do the molecules PCl_3 and NO2- have?
PCl3 has 2
NO2- has 1
Rank the strength of the IMFs from strongest to weakest:
HF CH₃OH CH₃CH₃ H₂CO
HF>CH3OH>H2CO>CH3CH3
A 50.0 g sample of hot metal at 145.0 °C is placed into a coffee-cup calorimeter containing 75.0 g of water at 22.0 °C. The final temperature of the water–metal system is 28.5 °C. Calculate the specific heat capacity of the metal.
The calorimeter has a calorimeter constant of 22.0 J/°C.
The specific heat of water is 4.184 J/g·°C.
0.375 J/g C
Identify whether the bond is ionic or covalent and its polarity:
KCl O2 NO
Electronegativity Values:
K: 0.8
Cl: 3.0
O: 3.5
N: 3.0
KCl: Ionic & polar
O2: Covalent & nonpolar
NO: Covalent & polar
You are given the following molecules:
CH₃OH (methanol)
CH₃CHO (acetaldehyde)
CH₃CH₃ (ethane)
a.) Rank the molecules from highest to lowest boiling
b.) Rank the molecules from highest to lowest vapor pressure
c.) Rank the molecules from highest to lowest surface tension
a.) CH₃OH>CH₃CHO>CH₃CH₃
b.) CH₃CH₃>CH₃CHO>CH₃OH
c.) CH₃OH>CH₃CHO>CH₃CH₃
Use the following chemical equations to determine ΔH° for the reaction:
C(graphite)+1/2 O2 (g)→CO (g)
Given equations:
C(graphite)+ O2 (g)→CO2 (g) ΔH∘=-393.5 kJ
CO (g)+1/2 O2 (g)→ CO2 (g) ΔH∘=-283.0 kJ
-110.5 KJ
Identify the bonds’ polarity and the number of sigma (σ) and pi (π) bonds that they have:
SO2 CCl4
SO2: polar, 2 sigma, and 1 pi
CCl4: nonpolar, 4 sigma, and 0 pi
The structure of polyester (PET) is shown below. PET can be formed from the ____ polymerization of _____ monomers. (See photo)
a. addition; one
b. addition; two
c. condensation; one
d. condensation; two
D
How much heat (in kJ) is required to convert 50.0 g of ice at −20.0 °C to steam at 50.0 °C?
Use the following data:
c_ice = 2.09" J/g°C
c_water = 4.184 J/g°C ΔH_fus =334 J/g
29.25 KJ
Complete the Lewis dot structure and identify polarity, resonance, hybridization, shape, and all bonds angles:
CH2O SF4
CH2O: resonance 1, sp2, trigonal planar, 120 degrees, and polar
SF4: resonance 1, sp3d, seesaw, 180 120 90 degrees, polar
A metal crystallizes in a body-centered cubic (BCC) unit cell. The edge length of the unit cell is 286 pm.
a.) How many atoms are in one unit cell?
b.) Calculate the atomic radius of the metal.
c.) If the molar mass of the metal is 52.0 g/mol, calculate its density.
d.) What is the coordination number?
a.) 2
b.) 124 pm
c.) 7.39 g/m3
d.) 8
Propane undergoes complete combustion in excess oxygen.
The balanced chemical equation for the reaction is:
C3H8 (g) + 5O2 (g) → 3CO2 (g) + 4H2O (l)
The standard enthalpies of formation (ΔH°) for the substances involved are:
ΔH∘ C3H8 =-103.8 KJ/mol
ΔH∘ CO2 =-393.5 KJ/mol
ΔH∘ H2O =-285.8 KJ/mol
Using the enthalpies of formation above, calculate the standard enthalpy change of combustion ΔH° for propane.
-2219 KJ/n