Chem Lab Final

Question 1

What is a ferrofluid?

Answer 1

A liquid that becomes strongly magnetized in the presence of a magnetic field.

Question 2

Explain the test for a ferrofluid

Answer 2

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

Question 3

Explain how to weigh by difference

Answer 3

*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.

Question 4

Explain gravity filtration

Answer 4

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

Question 5

Explain decanting

Answer 5

Removing the supernatural liquid from a solution by gently pouring it off or by withdrawing it using a medicine dropper

Question 6

Explain centrifuging

Answer 6

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

Question 7

Explain pipetting

Answer 7

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

Question 8

Explain the concept of buoyancy

Answer 8

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

Question 9

How do you determine density

Answer 9

divide mass (in air) by volume

Question 10

Explain pyrolysis

Answer 10

The process of causing a chemical reaction to occur by heating a substance open to atmospheric air

Question 11

What is Beer’s Law?

Answer 11

Beer’s Law states that the concentration of a chemical is directly proportional to the absorbance of a solution

Question 12

For litmus tests what color means what?

Answer 12

blue=base

pink=acid

Question 13

Study Solubility Rules

Answer 13

**

Question 14

Explain the detection of gas evolution.

Answer 14

**

Question 15

Explain the difference between equivalence point and end point

Answer 15

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)

Question 16

What is the chemical formula for soap?

Answer 16

C17H35CO2Na

Question 17

What is a micelle?

Answer 17

an aggregate of molecules in a colloidal solution, such as those formed by detergents

Question 18

Interpret the chemical reaction that forms soap scum?

Answer 18

Ca+2(aq) + 2C17H35CO2Na(aq) —> Ca(C17H35CO2)2(s) + 2Na+(aq)

(present in hard water) + (soap) –> (soap scum)

Question 19

Explain the causes of hard water

Answer 19

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

Question 20

How does one “soften” water?

Answer 20

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

Question 21

What are the ppm ranges for soft, moderately hard, and hard water?

Answer 21

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

Question 22

Explain the differences of titrating with soap solution vs. titration w/ EDTA and indicator

Answer 22

• 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.

Question 23

Contrast exothermic reactions vs endothermic reactions

Answer 23

exothermic reactions release heat while endothermic absorb heat

Question 24

List the fundamental precepts of calorimetry

Answer 24

• 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

Question 25

Recognize a combustion reaction

Answer 25

Combustion usually occurs when a hydrocarbon reacts with oxygen to produce carbon dioxide and water

Question 26

What are the productions formed in a combustion of a hydrocarbon?

Answer 26

CO2 and H2O

Question 27

List the ideal bond angles for the five basic geometries

Answer 27

Linear: 180
Trigonal Planar: 120
Tetrahedral:109.5
Trigonal bipyramidal: equatorial 90/axial 120
Octahedral:90

Question 28

Explain the differnece between intermolecular forces and intramolecular forces

Answer 28

Intermolecular forces are forces that exist between molecules while intramolecular forces are the forces that hold atoms together within a molecule

Question 29

Recognize and identify all intermolecular forces

Answer 29

**

Question 30

Rank intermolecular forces based on their strengths

Answer 30

Weakest- dispersion forces 
                 dipole induced-dipole 
                 dipole-dipole 
                 hydrogen bonds 
                 ion-dipole 
Strongest- ion-ion

Question 31

What is biodiesel?

Answer 31

a biofuel intended as a substitute for diesel

Question 32

What is the basic structure of biodiesel?

Answer 32

The biodiesel chemical formula is a combination of alkyl C12-C22 Fatty Acid Methyl Esters

Question 33

How do you make biodiesel?

Answer 33

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

Question 34

Describe the property of viscosity?

Answer 34

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

Question 35

How do intermolecular forces influence boiling points, melting points, viscosity, vapor pressure, evaporation rates, etc.?

Answer 35

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.