Fluids (Solution/Solubility) CH 5 &8 Flashcards
What is a fluid
Any material that has the ability to flow
Both liquid and gases are considered fluids
Hydrostatics
is the study of fluids that are NOT MOVING
Hydrodynamics
is the study of fluids that ARE MOVING
For hydrostatic fluids, what two properties are important to consider
density (p) and pressure (P)
If density is known, what is the formula to calculate for pressure
P = pgh
p=density
g=gravity
h=height
Density of water
1g/m^3 or 1g/cm^3
1000kg/m^3 or 1000kg/cm^3
8.33 lb/gal
1Pa =
Formula for hydrostatic pressure
p= density
g= gravity
h= height
Formula for pressure variation (pressure that accounts for top and bottom)
P2 = bottom
P1= top
Is pressure affected by container shape?
No, pressure is independent of container shape.
Pascal’s Principle states
If you apply external pressure to a confined fluid, that pressure is transmitted unchanged to every point within the fluid
Ex: if we increase P1 (top) by 5psi, the P2 (bottom) will be the original pressure plus 5psi
Buoyant Force states
all fluids exert a buoyant force on objects immersed in them
Normal Forces
Describes forces that are perpendicular to a surface
What is the Buoyant Force Formula
note: (pgV) represents weight (which is a force) of displaced fluid
Archimedes’ Principle states
An object immersed either totally or partially in a fluid feels a buoyant force equal to the weight of fluid displaced
Formula
Wapparent = Wtrue - Fb
If Density of object > Density of fluid, what will happen?
Object will sink
Fb < Wtrue
If Density of object < Density of fluid, what will happen?
Object will float
Fb > Wtrue
If Density of object = Density of fluid, what will happen?
Object will remain stationary in the fluid
Fb = Wtrue
Hydrometer is
a very simple device used to measure the specific gravity of liquids such as urine or milk
What are the 2 types of hydrodynamic flows
Laminar Flow
Turbulent Flow
Laminar flow is
unchanging flow pattern
smooth and orderly
Turbulent Flow is
continuously varying pattern flow
chaotic and abrupt
Flow rate is
the volume of fluid passing a particular point per unit of time
What is the SI unit of flow rate
m^3/s
What happens to the speed of water when diameter is made smaller?
It increases tremendously
decrease diameter = increase speed
assuming no leaks, volume and density will remain unchanged
Incomprehensible Fluids are
fluids whose volume or density do not change with pressure
What is the formula to calculate incomprehensible fluid flow rate?
aka The Continuity Equation
A1v1=A2v2
A= area
v= speed of incomprehensible fluid (flow rate)
Circular cross-sectional flow rate
Flow rate = Av=TTr^2v
A = TTr^2
v=speed of fluid (flow rate)
The Bernoulli Effect states
as the speed of a fluid increases, the pressure exerted by the fluid decreases
What is the Bernoulli Formula
pgh1 and pga 2 cancel out
Force equals
Pressure x Area
What is a Venturi tube flowmeter
Device used to measure fluid speed in pipes
What is the U-tube and what does it do?
U-tube is a manometer and we can use it to measure the differences in pressures (P1-P2)
What is the Venturi Tube Flowmeter Equation
What is the difference between ideal fluids and real fluids
Ideal fluids are those in which there is no loss of energy due to friction, no interactions between molecules, no interactions between molecules and pipe, tubing, or container.
Real fluids are what we deal with every day
What is viscosity
the measure of a fluid’s resistance to flow
What determines the speed of fluid through a pipe?
The closer a molecule to the wall, the slower it will move
Those closest to the center of the pipe will move the fastest
what must be introduced in order for real fluids to maintain flow?
A force
What is the equation for viscosity?
what is Poiseuille’s Equation?
Reynold’s Number is
A dimensionless qty that is used to characterize flow
If Nr < 2k = Laminar flow
If Nr > 3k = Turbulent flow
if between 2-3k= unstable
Reynold’s Number if formulated as
d= diameter of pipe
p=density
v=speed
n=viscosity
what is a solution?
a homogenous mixture of one or more solutes UNIFORMLY dispersed at the molecular or ionic level in a given solvent
What is homogenous mixture
it is not possible to discern phase boundaries between the components of the mixture
What is phase boundary
a boundary that separates/demarcates the regions of mixture where chemical or physical properties of the mixture change (ex vomit)
What is a solute
the material that gets dissolved (present in smaller quantities)
what is a solvent
the material that does the dissolving
Are all solutions liquids?
No, they can be liquid, gas or solid
What is molarity (M)?
molarity (molar concentration) is defined as the moles of a solute per liter of solution (Mass/Volume).
It is the most common concentration unit in chemistry
It is TEMPERATURE DEPENDENT
as temp goes up, volume goes up and molarity will decrease
What is Molality (m)?
Molality (molal concentration) expresses the concentration in terms of moles of solute per kg of solvent (mass/mass)
Mass is NOT temperature dependent, therefore molality is independent of this factor
Molality finds application in physical chemistry, often necessary to consider the quantities of solute and solvent separately, rather than as a mixture.
Are molarity and molality equal?
NEVER, but the differences become smaller as solutions become more dilute
What do you need to know in order to convert between molality and molarity?
Density of the solution
What is percent by weight to volume (%w/v)?
Defined as grams of solute per 100 mL of solution
What is percent by weight to weight (%w/w)?
Defined as grams of solute per 100g of solution
what is percent by volume to volume (%v/v)
never used because volumes are not additives
What is an equivalent (Eq) analogous to?
a mole (mol)
1 Eq = 1 mol
What is Normality analogous to?
Molarity (M)
When expressing the Eq of electrolyte cations, the number of Eq in a mol is equal to ?
The charge on the cation
Ex: Ca2+ has 2 cations, so 2Eq/mol
How do we solve for Normality (N) expressed in Eq/L ?
Remember Eq/L can go to mol/L because 1Eq=1mol and we use the number on the cation charge as the Eq/mol converting factor
ex: 0.40 Eq/L Ca2+ (2Eq/mol) so…
0.40Eq/L x mol/2Eq = 0.020 mol/L
Parts per million (PPM) is used when?
to express the concentration of extremely dilute solutions.
It is analogous to a percent except e are comparing the amount of g solute to a MILLION g of solution rather than 100g
1 mL = g?
1.06g = 1mL
1PPM = ? mg/L
1 mg/mL
What is solubility?
the amount of solute that will dissolve in a. given solvent at a given temperature
Define a saturated solution
solution that contains the max amount of solute it can absorb
Define supersturated
solution that contains more solute than allowed; unstable, will leak out of solution and either crystalize as a solid, separate as a liquid, or bubble out as a gas
What is the rule of thumb?
“Like dissolves Like”
polar solutes are more soluble in polar solvents
non polar solutes are more soluble in non polar solvents
Most polar species are ?
ionic compounds, followed by those that can form hydrogen bonds such as water and ethanol
What is energy change?
When a solute dissolves in a solvent, an associated energy change occurs, resulting in a change in temperature.
Energy change = Heat of the solution or Enthalpy of Solution
Define Enthalpy (H)
The energy change that accompanies dissolving exactly 1 mol of solute in a given solvent
Enthalpy is a state function
Enthalpy (H) = Energy (Q) as long as the pressure remains constatnt
If a solution process is endothermic, what happens to the energy of the system?
Energy is going INTO they system from the surroundings, so energy will INCREASE in the system; it will increase enthalpy (H)
If a solution process is exothermic, what happens to the energy of the system?
Energy is going OUT of the system onto the surrounding, so there is an energy loss. System cools, Enthalpy (H) will DECREASE
What is Coulomb’s law?
Opposite charges attract
What is solvation?
involves opposite charges coming toward each other through EXOTHERMIC process. Very messy process
What is lattice energy?
Energy required to separate 1 mol of an ionic compound into its constituent ions (cation/anion) in the gas phase
What determines if the heat of the solution is an endothermic or exothermic process
Depends on the relative magnitudes of the lattice energy and heat of solution (H)
If energy released by solvation < energy required to tear ions apart, then H = ENDOTHERMIC
If energy related by solvation > energy required to tear ions apart, then H = EXOTHERMIC
How does pressure affect solubility of a gas solute in a liquid solvent?
as pressure increases, solubility increases
How does pressure affect solubility of a solid or liquid?
Pressure has very little effect on solubility of solids and liquid solutes since they are NOT COMPRESSIBLE
What does Henry’s Law state?
if the pressure of a gas over liquid increases, then the amount of gas dissolved (solubility) in the liquid will increase proportionally
What is Henry’s constant Kh?
42mg/L/atm
or
0.042g/L/atm
How does the temperature affect solubility of solid and liquid solutes in liquid solvents?
as temp increases, solubility increases
How does the temperature affect solubility of gas solutes in liquid solutes?
as temp increases, solubility decreases
What are colligative properties
properties of solutions that DEPEND on the NUMBER of solute particles and NOT the IDENTITY of the solute particles
What are the 4 commonly cited colligative properties?
As concentration of solute increases:
1) Vapor pressure decreases
2) Boiling point increases
3) Freezing point decreases
4) Osmotic pressure increases (most dramatic!)
What results will vapor pressure have when the concentration of a solute increases
colligative property
the VP will decrease, which means more heat (Q) is needed to increase the VP to ambient pressure
What does Raoult’s Law state?
The vapor pressure of a volatile component of a solution (P) is qual to the vapor pressure of the pure substance (Pdegree) times the mole fraction (X) of that substance
Dalton’s law of partial pressure states
Total pressure of a mixture of gases is equal to the sum of the partial pressures of the individual component gases
Define boiling point
The temperature at which the vapor pressure of the material is equal to the ambient pressure
Change in the boiling point temperature is equal to what?
change in boiling point is directly proportional to the molar concentration of the solute particles
What is the Ebullioscopic constant (Kbp) of water?
0.512 (degrees C)/molal (m)
What is the freezing point
Freezing point (or melting point) of a sample is the temperature at which the liquid phase of the material is in equilibrium with the solid phase
What is the cryoscopic constant (Kfp) of water
1.86 (degrees C)/molal (m)
Describe the levels of tonicity (isotonic, hypertonic, hypotonic)
What is osmotic pressure (TT)?
The drive for the concentration of water to equalize.
Where,
TT=MRT
TT=Osmotic Pressure
M=Molarity
R= Ideal gas constant
T= Absolute temperature
What is the ideal gas constant (R)?
0.08206 (Lxatm)/(mol/K)
What are colloids?
Consist of one phase uniformity dispersed in a second phase
Not true solutions
particles are larger! (x100-1000s)
Cannot be filtered and do not settle out of solution
Have Tyndall effect
What is the Tyndall effect?
When shine a light, particles are large enough to scatter
Types of colloids
Blood, protiens, starch (hetastarch), milk
