Ch 10 - Thermo
If the ∆Hrxn of the combustion of ethene equals -1449.7 kJ/mol. Is the combustion reaction endothermic or exothermic?
Exothermic
Neon gas is heated in a closed rigid container. What will happen to the gases pressure and density?
(increases/decreases/remains constant)
Pressure increases
Density remains constant
Sublimation
What are the 4 colligative properties?
When the concentration of solute INCREASES, what happens for each property?
Freezing point depression (FP lowers)
boiling point elevation (BP raises)
vapor pressure (VP lowers)
osmotic pressure (π increases)
Nav App: This water treatment method applies pressure in order to purify water aboard ships
Reverse Osmosis
If a gas were to expand from 2L to 7L against a pressure of 6 atm, was the work done BY the gas or ON the gas?
By the gas
Air is normally 78% N2, 21% O2, 0.9% Ar and 0.1% of trace gases. A certain sample of gas is found to consist of 156 g of N2, 42 g of O2 and 11 g of Ar. What is the mole fraction of the Ar gas in this sample?
3.8 x 10-2
Place these liquids in order of increasing solubility in water. dimethyl ether (CH3OCH3), propane (C3H8), ethanol (CH3CH2OH)
propane < dimethyl ether < ethanol
Rank from LOWEST TO HIGHEST for vapor pressure of water:
A 1 mole of CH3OH in water
B 1 mole HCl in water
C 1 mole Mg(NO3)2 in water
C < B < A
Nav App: Naval Fuel JP-5 is less flammable than Jet-A. Which would have a higher vapor pressure?
Jet A
How much heat does it take to raise the temperature of 36 g of Cu metal from 25oC to 47oC? (s = 0.40 J/gºC)
3.2 x 102 J
You have a balloon in a room at 25oC containing 2.0 mol of H2 gas and 1.0 mol of N2 gas. If the total pressure of the balloon was 4.5 atm, what are the partial pressures of H2 and N2, respectively?
3.0 atm, 1.5 atm
If you have a gas at a temperature and pressure below its triple point, what do you need to do in order to turn it into a liquid?
Increase Temp, Increase Pressure
What is the Kb of a solvent, given that when in a 3.0 molal solution, the change in boiling point increases by 5.15ºC?
1.72 ºC/m
Lab 30B Which fuel would be expected to have the LOWEST fuel value?
a. Octane (C8H18)
b. Pentanol (C5H12O)
c. Ethanol (C2H6O)
Ethanol (highest %O by mass)
The combustion reaction of the amino acid glycine (C2H5O2N),is: 4C2H5O2N(s)+ 9O2(g) --> 8CO2(g)+ 10H2O(l)+ 2N2(g); ∆Hrxn= -3857 kJ/mol
If ∆Hf [CO2(g)]=-393.5 kJ/mol and ∆Hf [H2O(g)]= -285.8 kJ/mol, calculate ∆Hf of glycine.
-2149 kJ/mol for 4 glycine
=-537.25 kJ/mol for 1 glycine
A chamber contains 2.73 moles of gas at 879 mmHg and 5oC. What is the volume of the chamber?
53.9 L
Which would have the highest surface tension?
A.carbon tetrachloride, CCl4
B.hexane, CH3CH2CH2CH2CH2CH3
C.octane, CH3CH2CH2CH2CH2CH2CH2CH3
D.glycerol, HC(CH2OH)2OH
Glycerol - H-bonding is strongest IMF!
What is the molality of an aqueous solution, if the new freezing point is -3.8ºC? Kf of water = 1.86ºC/m
2.04 m
Lab 12Z: A plot for heptane's evaporation, lnP vs. 1/T gives the best fit line: ln P = -6227.29 (1/T) + 5.34 (R2 = 0.898).
If the slope of the line represents -∆Hvap/R, what is the enthalpy of vaporization for heptane?
51.773 kJ/mol
An Fe rod (sFe = 0.45 J/goC) weighing 200 g at 80oC is placed into 1500 mL of water at 10oC. Calculate the temperature when the iron and water (sH2O = 4.18 J/gºC) reach thermal equilibrium.
10.99oC
A balloon is filled with a 307g of a certain gas at 25ºC. If the density of the gas is 1.393 g/L and the pressure is 1.00 atm, how large is the balloon?
220 L
How much energy in kJ is required to melt 30 g of ice starting at -10ºC? (sice = 2.11 J/gºC; ∆fusH = 6.01 kJ/mol)
633 J +10,017 J = 10,650 J = 10.7 kJ
A 0.55 g sample of a non-electrolyte is dissolved in 5.31 g of lauric acid (Kf = 3.9ºC/m). The freezing point depression is determined to be 4.20ºC. What is the molar mass of this compound?
96.2 g/mol
Nav App: The explosion rxn of TNAZ is:
C3H4N4O6 --> CO2 + 2 CO + 2 H2O + 2 N2 (all gases)
If 5.00 mol of TNAZ explode in a 25.0 L container at a temp of 6529 ºC, what is the pressure exerted on the container?
P = nRT/V
=35 * .08206 * 6802 / 25
=781 atm