Chem Lab Final Flashcards
What is a ferrofluid?
A liquid that becomes strongly magnetized in the presence of a magnetic field.
Explain the test for a ferrofluid
Measure a liquid volume with a graduated cylinder, mix the mixture on a stir plate. Use Gravity Filtration, pipet the liquid, decant from your PPT, centrifuge your substance, test to see if the ferrofluid is magnetic
Explain how to weigh by difference
*always use the same balance. This is the most accurate weighing method. Repetitive amount of weighing to determine how much of the original solution was transferred, destroyed, or lost.
Explain gravity filtration
Wetting a piece of filter paper folded into a funnel over a flask, this is held together by a clamp or a ring stand. Pour the filtrate into the paper funnel, then try and filter whatever is there using distilled water
Explain decanting
Removing the supernatural liquid from a solution by gently pouring it off or by withdrawing it using a medicine dropper
Explain centrifuging
Placing a test tube with a sample in the centrifuge to balance the centrifuge place another test tube opposite of your tube, spin for a minute and allow centrifuge to stop on its own, then remove the supernatant liquid
Explain pipetting
Wash pipet with liquid being pipetted, using a pipet pump fill to 1ml above desired amount needing to be pipetted , slowly turn wheel to desired drain rate, let drain as desired
Explain the concept of buoyancy
According to the principle of buoyancy, any object immersed in a measured amount of water is pushed upward by a force equal to the weight of water displaced by the object
How do you determine density
divide mass (in air) by volume
Explain pyrolysis
The process of causing a chemical reaction to occur by heating a substance open to atmospheric air
What is Beer’s Law?
Beer’s Law states that the concentration of a chemical is directly proportional to the absorbance of a solution
For litmus tests what color means what?
blue=base
pink=acid
Study Solubility Rules
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Explain the detection of gas evolution.
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Explain the difference between equivalence point and end point
The equivalence point is defined as the point in the titration where stoichiometric amounts of both reagents are present (enough base has been added to neutralize all the acid) while the end-point is defined as the point in the titration where the indicator changes color (proper indicator has endpoint at or about same pH as equivalence point)
What is the chemical formula for soap?
C17H35CO2Na
What is a micelle?
an aggregate of molecules in a colloidal solution, such as those formed by detergents
Interpret the chemical reaction that forms soap scum?
Ca+2(aq) + 2C17H35CO2Na(aq) —> Ca(C17H35CO2)2(s) + 2Na+(aq)
(present in hard water) + (soap) –> (soap scum)
Explain the causes of hard water
Hardness in water is caused by the presence of dissolved calcium, magnesium, and iron(II/III) salts. Hardness ions in water react with soap to form insoluble compounds causing a waste of soap
How does one “soften” water?
is softened by exchanging its calcium and magnesium ions with sodium ions, to accomplish this, the hard water is passed through a column of cation exchanger containing sodium ions
What are the ppm ranges for soft, moderately hard, and hard water?
Soft: if the concentration of dissolved salts is less than 100 ppm
Moderately hard: between 100-200ppm
Hard: concentration of dissolved salts is greater than 200ppm
Explain the differences of titrating with soap solution vs. titration w/ EDTA and indicator
- The soap solution precipitates the hardness ions, whereas the EDTA complexes the hardness ions
- The end-point in the soap is the point at which all hardness ions have been precipitated by the soap and can be observed visually w/ permanent suds
- The end-point in the EDTA is detected by use of the indicator Black T.
Contrast exothermic reactions vs endothermic reactions
exothermic reactions release heat while endothermic absorb heat
List the fundamental precepts of calorimetry
- Law of Conservation of Energy: the sum of all the energies (heats) must equal zero, Heat going into a system is positive, Heat leaving a system is negative
- q=mxCpxDeltaT
- T=Tf-Ti
- q=KxDeltaT
- First Law: qgained+qlost=0
Recognize a combustion reaction
Combustion usually occurs when a hydrocarbon reacts with oxygen to produce carbon dioxide and water
What are the productions formed in a combustion of a hydrocarbon?
CO2 and H2O
List the ideal bond angles for the five basic geometries
Linear: 180 Trigonal Planar: 120 Tetrahedral:109.5 Trigonal bipyramidal: equatorial 90/axial 120 Octahedral:90
Explain the differnece between intermolecular forces and intramolecular forces
Intermolecular forces are forces that exist between molecules while intramolecular forces are the forces that hold atoms together within a molecule
Recognize and identify all intermolecular forces
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Rank intermolecular forces based on their strengths
Weakest- dispersion forces
dipole induced-dipole
dipole-dipole
hydrogen bonds
ion-dipole
Strongest- ion-ionWhat is biodiesel?
a biofuel intended as a substitute for diesel
What is the basic structure of biodiesel?
The biodiesel chemical formula is a combination of alkyl C12-C22 Fatty Acid Methyl Esters
How do you make biodiesel?
To make Biodiesel, a catalyst is needed; either Potassium Hydroxide (KOH) or Sodium Hydroxide (NaOH). The catalyst is then dissolved into methanol to create what is called methoxide. The oil is heated and the methoxide is mixed in and the chemical reaction begins
Describe the property of viscosity?
Viscosity is another type of bulk property defined as a liquid’s resistance to flow. When the intermolecular forces of attraction are strong within a liquid, there is a larger viscosity
How do intermolecular forces influence boiling points, melting points, viscosity, vapor pressure, evaporation rates, etc.?
Boiling points are a measure of intermolecular forces.
The intermolecular forces increase with increasing polarization of bonds. The strength of intermolecular forces (and therefore impact on boiling points) is ionic > hydrogen bonding > dipole dipole > dispersion
Boiling point increases with molecular weight, and with surface area.
They are, however, strong enough to control physical properties such as boiling and melting points, vapor pressures, and viscosities.
