Phases and Gases Flashcards
What is stronger, a ion-dipole interaction or a H bond interaction?
ion-dipole interaction is stronger
an increase in entropy is a __1__ value, while a decrease in entropy is a __2__ value
1) + 2) -
How does an increase in IMF affect density
increase in IMF indicates increased density of a substance
Name the process of phase change: 1) solid to liquid 2) liquid to gas 3) gas to solid 4) solid to gas
1) fusion 2) vaporization 3) deposition 4) sublimation
When a gas becomes a solid, does KE increase or decrease? How about entropy? Is this an endo or exothermic rxn?
KE decreases entropy decreases exothermic rxn (bcz your forming bonds, which expels energy)
What is the triple point and critical point of an phase diagram?
triple point: solid, liquid, and gas of that substance coexist in equillibrium (note this doesn’t necessarily mean in equal amounts) critical point: the point where P & Temp difference between liquid and gas is no longer distinct
How does the phase diagram of water differ from the phase diagram of most other substances?
-the slope between solid and liquid is a negative slope, compared to most substances which have a positive slope -this indicates that increased pressure actually promotes the liquid form over the solid form of water (this is because the solid form is less dense than the liquid form). this is the reason why you can glide over ice with ice skates
What is calorimetry?
calorimetry measures changes in heat transfer in a chemical rxn
Distinguish between a bomb, constant pressure, and low tech calorimeter.
bomb calorimeter: measures energy change at a constant volume (therefore allows for changes in pressure) constant pressure calorimeter maintains constant pressure low tech calorimeter: i.e. coffee cup (which maintains contsant pressure) side note: enthalpy changes are the changes in energy at constant pressures. therefore, you cannot use a bomb calorimeter to measure enthalpy.
what is specific heat?
the amount of heat required to raise the temp of 1gram of a substance by 1 degree celsius
what is q in q=mc∆T?
q is change in heat, or change in enthalpy (when pressure is held constant)
When 2 compounds are reacted together and there is a positive change in temperature (aka temperature increases), does this indicate an exothermic or endothermic rxn
exothermic
What are the plateau lines on a heating curve indicate?
the phase changes of that substance. not that these are the areas where heat is added, but the temperature of the substance itself is not increasing. the substance must undergo the phase change before you can further again increase the temperature
What is the first plateau and the second plateau of a heating curve indicate
first plateau - heat of fusion second plateau - heat of vaporization
Is heat of fusion or heat of vaporization higher in value?
heat of vaporization is always higher in value than heat of fusion for all substances
C = mc = heat capacity What is C?
C is usually used and referred to when using a calorimeter
The harder it is to raise the temperature of a substance, the ____ (lower or higher) the value of specific heat, c, will be
higher
Substance A has a lower specific heat than substance B. Which substance will be easier to raise the temperature of that substance?
Raising the temperature of Substance A will be easier
Is the specific heat value for a substance always the same value?
no. the specific heat value will depend on the phase that the substance is in.
As a density of a substance increases, the volume of that substance will _____(decrease or increase)
decrease density and volume are inversely related
What type of relationship does density have to pressure, temperature, and IMF
Density is directly related to pressure, indirectly related to temperature, and directly related to IMF
What is vapor pressure?
the force exerted by the gas particles that vaporize from a solid or liquid sample
is vapor pressure affected by external pressure?
no. the vapor pressure is regarding the pressure that the gas of a substance exerts on that substance, which does not include the pressure of the external environment that is exerted on the substance.
How is vapor pressure related to temperature and IMF?
vapor pressure is directly related to temperature (as temp increases, vapor pressure increases) vapor pressure is indirectly related to IMF (the more IMF of a substance, aka the more polar the substance is, the less the vapor pressure value will be of that substance)
What is the relationship between the vapor pressure of water at sea level compared to the vapor pressure of water on top of Mt Everest
vapor pressure will be the same, as vapor pressure is not affected by external (atmospheric) pressure
Boiling Point of a substance occurs when which 2 pressures are equal to each other?
BP occurs when the vapor pressure equals atmospheric pressure
How does increased atmospheric pressure affect the BP of that substance?
A higher atmospheric pressure will increase the BP temperature of that substance. i.e. water boils at a higher temperature at sea level than it does on top of Mt Everest
Why does it take less energy to boil water at higher altitudes compared to when at sea level?
The vapor pressure of water is constant. The amount of energy required to raise the vapor pressure of water to a lower external pressure is going to require less energy compared to an atmospheric pressure that is higher. Atmospheric pressure is lower at higher altitudes and thus takes less energy to raise the vapor pressure to equal the atmospheric pressure
Ethanol has less IMF than water. What does this tell you about the BP of ethanol compared to water?
decrease IMF will decrease the BP. Thus, ethanol will have a lower BP (and lower MP) than water
If you increase the pressure of most substances, will this usually increase or decrease the MP/FP?
For most substances, increasing pressure will increase the MP/FP (Note that the most common exception is water)
Is pressure directly or inversely related to MP/FP?
For most substances, P is directly r/t MP/FP.
The substance with the highest freezing point will have the ____ (lowest/highest) IMF
highest i.e. water has a higher freezing point compared to ethanol. this is because although both are polar molecules, water can create 4 H bonds, while ethanol can only make 3)
An ideal gas has ____ IMF
zero meaning that ideal gases do not interact with each other; they do not attract nor repel each other
An ideal gas undergoes _____ collisions
elastic (the gas molecules do not lose energy when they collide into the sides of a container; this creates pressure)
An ideal gas has an average KE proportional to its ____
temperature
Ideality of gases is favored with high temperature and low pressure since interactions of the particles are _____
minimized
In addition to noble gases, name 3 other gases that act like ideal gases
N2, H2, O2
Avagadros Law: the volume of an ideal gase is proportional to the # particles in the container at a given P and Temp, regardless of the identity of the gas. Therefore, volume of an ideal gas is directly or inversly r/t n (# moles)
directly r/t n
1 mole of any ideal gas occupies ____L at STP
22.4 STP = 273K/0celsius and 1 atm
Boyles Law
P1xV1 = P2xV2 In other words, P is inversely r/t Volume when at constant temp and #moles (n)
Charles Law
V1/T1 = V2/T2 In other words, V and temp are directly related at constant temp and #moles (n)
What is the ideal gas law?
PV = nRT
1 atm = ____ kPa = ____ torr = ____ mm Hg
101kPa 760 torr 760 mm Hg
1L = 1000mL = ____cm^3 = ____m^3
1000 cm^3 0.001 m^3
What is the volume of 0.25mol He @ 25 degrees Celsius & 725 torr?
instead of converting torr to atm and using PV = nRT equation, it is good enough in this instance to estimate STP values: 0 degrees celsius and 760 torr. At STP, 1 mol gas = 22.4L. Therefore, 0.25mol @ STP = 22.4 x 1/4 = 5.5L Real value = 6.2
How do real gases compare to ideal gases in relation to IMF and collisions?
real gases are influenced by IMF and their frequency of collisions are NOT elastic, thus their collisions with the side of the container decrease pressure. the pressure of an ideal gas is greater than the pressure of a real gas
How does the volume of an ideal gas compare to the volume of a real gas
V ideal > V real This is because real gases have a physical size and take up space in the container; therefore free space in the container is smaller
In the real gas law, what do a and b stand for
a = attraction force of molecules to each other (increased IMF increases a) b = “bigness” of the gas molecules
Of F2 and Cl2, which one will be more likely to act like an ideal gas?
F2 because it is smaller in size
How is Partial pressure, Pa, of a gas calculated?
Pa = Xa x Ptotal
Xa = mole fraction of substance = # moles of a molecule / total # of moles in substance
If calculating Pa at STP, then Pa = Xa because Ptotal = Patm = 1 atm
Do heavier or lighter gas particles move more quickly?
Lighter gas molecules move more quickly than heavier gas molecules
