Gas Laws
P, V, T, & W
Enthalpy
Calculations
Definitions
100
What is the ideal gas equation and what do each of the variables stand for?
PV=nRT Pressure volume n=number of moles R= gas constant=0.082057 L*atm/(mol*K) Temperature
100
What is the equation for pressure and what does each variable represent?
P = F/A P = pressure F = force A = area
100
Define enthalpy
used to quantify the heat flow into or out of a system in a process that occurs at constant pressure. It is equal to the potential energy of product bonds−potential energy of reactant bonds It is also equal to the energy added to break reactant bonds+energy released when making product bonds
100
A gas takes up 14.8 liters of 24oC. What temperature in kelvin is required to obtain a volume of 25.0 liters at constant pressure?
P1 = 0.956 atm
100
What are the physical characteristics of gases?
Assume volume and shape Most compressible state of matter Mix evenly and completely Have much lower densities than liquids and solids
200
What is the density equation? Using the density equation, solve the following problem: Rocks are sometimes used along coasts to prevent erosion. If a rock needs to weigh 2,000 kilograms (about 2 tons) in order not to be shifted by waves, how big (what volume) does it need to be? You are using basalt, which has a typical density of 3200 kg/m3.
d = m/V V = 0.625 m3
200
When the gas in a system does work, the volume of a gas increases (ΔV>0) and the work done is negative. True/False and Why
True. If the system does work on the surroundings, that would decrease the internal energy in the system and work would be negative.
200
The thermite reaction involves aluminum and iron(III) oxide 2Al
15.25 kJ/g
200
Calculate the root mean square velocity of hydrogen gas at 25 C.
1928 m/s
200
Name and define at least 3 different types of energies
Radiant energy comes from the sun and is earth’s primary energy source Thermal energy is the energy associated with the random motion of atoms and molecules Chemical energy is the energy stored within the bonds of chemical substances Nuclear energy is the energy stored within the collection of neutrons and protons in the atom Potential energy is the energy available by virtue of an object’s position
300
What is the equation for solving the molar mass? Using the equation, solve the following problem: A gaseous sample of a compound has a density of 0.977 g/L at 710.0 torr and 100.00 C. What is the molar mass of this compound?
M = dRT/P 32.0 g/mol
300
A gas takes up 25.2 liters at 25oC. At 25oC, the gas can also take up 12.2 liters at 1500 torr. What was the pressure, in atm, of the original sample?
0.658 L
300
Define Bond enthalpy (also known as bond-dissociation enthalpy, average bond energy, or bond strength)
The enthalpy change required to break a particular bond in one mole of gaseous molecules
300
What is the pressure (in atm) exerted by 2 moles of a gas in a container with a volume of 6.5 L at 65°C
8.54 atm
300
Define gas diffusion and give its equation.
The gradual mixing of molecules of one gas with molecules of another by virtue of their kinetic properties.
400
What is the partial pressure equation and what does each variable represent? Using the equation, answer the following problem: A mixture of gases contains 4.46 moles of neon _Ne_ , 0.74 mole of argon _Ar_ , and 2.15 moles of xenon _Xe_ . Calculate the partial pressures of the gases if the total pressure is 2.00 atm at a certain temperature.
Pi = XiPT Pi = partial pressure Xi= mole fraction PT = total pressure
400
25 liters of gas A is pumped into a container at 25 C and 760 torr with 20 liters of gas B at 25 C and 700 torr. Calculate the total pressure when both gases are pumped into a tank with 10 liters at 25 C.
13.76 L
400
Part 1:What is Hess's Law? Part 2: What is enthalpy of solution?
1: When reactants are converted to products, the change in enthalpy is the same whether the reaction takes place in one step or in a series of steps. 2:The heat generated or absorbed when the solute dissolves in the solvent
400
What is the change in internal energy when 2 moles of CO are converted to 2 moles of CO2 at 1 atm and 25°C. equation: 2CO(g) + O2(g) --> 2CO2(g). ΔH=-566
-563.5 kJ/mol
400
What is a resonance structure?
A resonance structure is one of two or more Lewis structures for a single molecule that cannot be represented accurately by only one Lewis structure.
500
What is the root-mean-square speed equation? Using the equation, solve the following problem: Calculate the root-mean-square speeds of helium atoms in m/s at 25° C.
Urms = sqr(3RT/M) 1.36×10^3 m/s
500
Imagine a bicycle pump. We will assume that the air in the bicycle pump can be approximated as an ideal gas in a piston. We can do work on the air in the pump by compressing it. Initially, the gas has a volume of 3.00L. We apply a constant external pressure of 1.10 atm to push down the handle of the bike pump until the gas is compressed to a volume of 2.50L. How much work did we do on the gas?
0.55 L*atm or 56 J
500
Describe the difference between endothermic reactions and exothermic reactions Is ΔH positive or negative for each? given this reaction: H2(g)+F2(g)=2HF if the bond energies (in kJ) for H2, F2, and HF are 436, 158, and 568 kJ/mol respectively, is the reaction exo or endothermic?
Exothermic process is any process that gives off heat – transfers thermal energy from the system to the surroundings. ΔH is negative Endothermic process is any process in which heat has to be supplied to the system from the surroundings. ΔH is positive In this reaction, ΔH is negative (-542 kJ), so it is exothermic.
500
We have a balloon of argon gas which has a volume of 2.3 L. The gas transfers 485 J of heat to the surroundings and the final volume of the system is 2.05 L. If the external pressure is 1.01x10^5 Pa, what is the ∆U (change in internal E)?
-460 J
500
What is the difference between specific heat and heat capacity?
The specific heat(s) of a substance is the amount of heat (q) required to raise the temperature of one gram of the substance by one degree Celsius. The heat capacity (C) of a substance is the amount of heat (q) required to raise the temperature of a given quantity (m) of the substance by one degree Celsius.
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