Specific heat and heat transfer
Which signs on q and w represent a system that is doing work on the surroundings, as well as losing heat to the surroundings?
q = -
w = -
What type of reaction has a positive ΔH and absorbs heat from its surroundings?
An endothermic reaction
Name the 4 gas law relationships
Pressure and Temperature (direct) P1/T1 = P2T2
Amount and Volume (direct) n1/V1 = n2/V2
Volume and Temperature (direct) V1/T1 = V2/T2
Pressure and Volume (inverse) P1V1 = P2V2
What type of intermolecular forces are present in a sample of HBr?
Dispersion and Dipole-Dipole
Name one study technique and one non-study habit you plan on implementing for this midterm
Great. Don't forget to sleep early and drink plenty of water!
How much heat is released when 1.00 kg of aluminum (0.903 J/g C) cools from 35.0 oC to 20.0 oC?
q = (1000.0 g)(0.903 J/g C) (20.0 oC - 35.0 oC)
q = -13500 J
C3H8 (g) + 5 O2 (g) → 4 H2O (g) + 3 CO2 (g)
ΔHrxn = -2044 kJ
Calculate the total amount of heat produced when 1.04 x 104 g of propane is burned
482000 kJ
In an experiment you fill a 6.00 L container with 7.13 g of methane (CH4) at 19 oC, what is the gas pressure?
(0.445 mol)(0.08206 (L atm/ mol K))(292.15)
/ (6.00L) = 1.78 atm
Rank each of the following groups of substances in order of increasing boiling point
NH3, He, CH3F, CH4
He < CH4 < CH3F < NH3
What is the difference between bond energies and standard formation?
Bond energy refers to to how much energy is required to break or form a covalent bond between two atoms.
ΔHrxn=∑(bond energies of bonds broken)−∑(bond energies of bonds formed)
Standard formation is the change in enthalpy when 1 mole of the compound forms from reactants in their standard states.
ΔHrxn=∑ΔHf∘(products)−∑ΔHf∘(reactants)
It takes 221 J of energy to raise the temperature of 55.3 g of a metal from 30.0 oC to 47.0 oC. What is the metal?
A. Aluminum (0.903 J/g C)
B. Iron (0.449 J/g C)
C. Lead (0.128 J/g C)
D. Silver (0.235 J/g C)
D. Silver
C12H22O11(s) + 12 O2(g) → 12 CO2(g) + 11 H2O (g)
What is the ΔHfo of the reaction?
C12H22O11: -2226.1 kJ/mol
CO2: -393.5 kJ/mol
H2O: -241.8 kJ/mol
𝟏𝟐 𝒎𝒐𝒍 𝒙 (−𝟑𝟗𝟑.𝟓 𝒌𝑱/𝒎𝒐𝒍)) + (𝟏𝟏 𝒎𝒐𝒍 𝒙 (−𝟐𝟒𝟏.𝟖 𝒌𝑱/𝒎𝒐𝒍))] − [ (𝟏 𝒎𝒐𝒍 𝒙 (−𝟐𝟐𝟐𝟔.𝟏 𝒌𝑱/ 𝒎𝒐𝒍)) + (𝟏𝟐 𝒎𝒐𝒍 𝒙 (𝟎 𝒌𝑱/𝒎𝒐𝒍))]
= −𝟓𝟏𝟓𝟓. 𝟕 𝒌𝑱
Calculate the molar mass of a gas if 2.50g occupies 0.875 L at 685 torr and 35 oC
n = 0.0312 mol
2.50g / 0.0312mol = 80.2 g/mol
Rank the following groups in order of increasing boiling point
CH3CH2Cl, CH3CH3, CH4, CH3CH2OH
CH4 < CH3CH3 < CH3CH2Cl < CH3CH2OH
A balloon is heated by adding 0.655 kJ of heat, it expands on heating and the balloon does 382 J of work on the atmosphere. What are the values of q, w, and ΔE?
𝒒 = +𝟎. 𝟔𝟓𝟓𝒌𝑱
𝒘 = −𝟑𝟖𝟐𝑱
∆𝑬 = 𝟔𝟓𝟓𝑱 + (−𝟑𝟖𝟐𝑱) = 𝟐𝟕𝟑 J
100.0g of an unknown metal at 150 oC was dropped in a bucket containing 50.0g of water initially at 21 oC. The final temperature of the mixture is 32 oC. What is the specific heat capacity of the unknown metal?
(100.0g) Cs (32 -150 oC) = -(50.0g) (4.18 J/g C) (32-21 oC)
Cs = 0.195 J/g C
CH3CH2OH (g) + HCl (g) → CH3CH3Cl (g) + H2O (g)
What is the ΔH of this reaction?
C-H: 414 kJ/mol
C-C 347 kJ/mol
C-O 360 kJ/mol
O-H 464 kJ/mol
H-Cl: 431 kJ/mol
C-Cl: 339 kJ/mol
Reactants: 2070 kJ + 347 kJ + 360 kJ + 464 kJ + 431 kJ = 3672 kJ
Products: 2070 kJ + 347 kJ + 339 kJ + 928 kJ = 3684 kJ
3672 kJ - 3684 kJ = -12 kJ
A gas has a density of 1.43 g/L at 25 oC and a pressure of 0.789 atm. What is the molar mass of the gas?
𝑽/𝒏 = 𝑹𝑻/𝑷 = (𝟎.𝟎𝟖𝟐𝟎𝟔 𝑳 ∙ 𝒂𝒕𝒎/𝒎𝒐𝒍 ∙ 𝑲) (𝟐𝟕𝟑. 𝟏𝟓 + 𝟐𝟑 𝑲) 𝟎.𝟕𝟖𝟗 𝒂𝒕𝒎 = 𝟑𝟎.𝟖 𝑳/𝒎𝒐𝒍 𝒙 𝟏.𝟒𝟑 𝒈/𝟏 𝑳
= 𝟒𝟒. 𝟎 𝒈/𝒎𝒐𝒍
Which of the following compounds exhibits hydrogen bonding?
A. CH3I
B. HBr
C. CH3OCH3
D. CH3NH2
D. CH3NH2
56.0g N2 and 96.0g O2 are mixed in a 2.0L container at 300K. Calculate the partial pressure of each gas and the total pressure.
PN2 = 24.6 atm
PO2 = 36.9 atm
Ptotal = 24.6atm + 36.9atm = 61.5 atm
50.0 mL of ethanol (density: 0.798 g/mL), initially at 7.0 oC, is mixed with 50.0mL of water (density: 1.00 g/mL), initially at 28.4 oC, in an insulated beaker. Assuming that no heat is lost, what is the final temperature of the mixture?
Ethanol Cs : 2.42 J/g C
Water Cs : 4.18 J/g C
(39.9 g)(2.42 J/g C)∆𝑻 = -(50.0g)(4.18 J/g C)∆𝑻
Tf = 21.6 oC
How much energy is required to heat 36.0 g H2O from a liquid at 65°C to a gas at 115°C?
Cs (liquid): 4.18 J/g C
ΔHvap: 40.7 kJ/mol
Cs (steam): 2.01 J/g C
q(liquid) = 5.27 kJ
q (vaporization) = 81.3 kJ
q (steam) = 1.08 kJ
qtot = 87.7 kJ
A deep-sea diver uses a gas cylinder with a volume of 10.0 L that contains 51.2 g of O2 and 32.6 g of He. Calculate the partial pressure of each gas and the total pressure if the temperature of the gases is 19°C.
Po2 = 3.83 atm
PHe = 19.5 atm
Ptot = 19.5 atm + 3.83 atm = 23.3 atm
Explain what each of the intermolecular forces are, what they're present in, and rank them according to strength
1. Dispersion: all molecules and atoms
2. Dipole-Dipole: polar molecules
3. H-bonding: molecules containing H bonded to F, O, or N
How much heat is released when 150.0g of water is cooled from 85.0 oC to -110.0 oC?
H2O (l): 4.18 J/g C
H2O (s): 2.09 J/g C
ΔHfus: 6.02 kJ/mol
(hint: the heat of fusion is for going from solid to liquid)
q = (150.0g)(4.18 J/gC)(0 - 85 oC) = -53300 J
q = (150.0g x (1mol /18.02g)) (-6.02 kJ/mol) = -50.1 kJ
𝒒 = (𝟏𝟓𝟎.𝟎 𝒈) (𝟐. 𝟎𝟗 𝑱/𝒈 ∙ °𝑪) (−𝟏𝟏𝟎.𝟎 °𝑪 − 𝟎.𝟎 °𝑪) = −𝟑𝟒𝟓𝟎𝟎 𝑱
𝒒tot = −𝟓𝟑.𝟑 𝒌𝑱 + (−𝟓𝟎.𝟏 𝒌𝑱) + (−𝟑𝟒.𝟓 𝒌𝑱) = −𝟏𝟑𝟕.𝟗 𝒌𝑱