CHEM 101 Lab Flashcards
(33 cards)
What is heat capacity?
the amount of heat needed to change it’s temperature by a degree
C = q/(Tf - Ti) C = c*(mass of substance) C = Cm*(moles of substance) C = change in H/(Tf - Ti)
How do you read a graph like the one in Lab 1?
to get the extrapolated temperature Te, you must extrapolate (using a straight line through the decreasing temperatures) back to the y axis where t = 0
then setting Tf equal to Te you can calculate (Tf - Ti)
What is the experiment procedure of the heat capacity of the metal block?
make a water bath by putting 200 mL of distilled water into a 400 mL beaker
assemble the calorimeter
transfer the metal block into the calorimeter
What is the experimental procedure of the heat capacity of 2-PrOH?
use a thermometer to check the temperature of the distilled water in the 400 mL beaker
measure about 70 mL of PrOH into a graduated cylinder
put the metal block into the hot water
What is the experimental procedure of the enthalpy of fusion (melting) of ice?
measure out 50 mL of distilled water into graduated cylinder
half fill a 250 mL beaker with ice
transfer a large scoop of ice into the calorimeter
reweigh the cups and their contents
What are common applications of light emissions of elements?
flame tests
fireworks
office fluorescent lights
What is the speed of light?
2.998 * 10^8 m/s
What is Plank’s Constant?
6.626 * 10^-34
What is a spectrometer?
the light from the source is split into a narrow range of wavelengths passed through a sample
some of that must be absorbed
a function A called absorbance is directly related to the amount of absorbance
a larger A value means that more of the incident light is absorbed
What is the experimental procedure of hydrogen, helium, and neon discharge tubes?
to observe the line spectra, set the square hole of the spectroscope at the middle of, and almost touching, the discharge tube
if you hold it too far away you’ll see the lines for the overhead fluorescent lights in the lab room
What is the experimental procedure of the flame tests?
clean the Pt wire using a burner by placing just the tip into HCl and then heating the tip in the flame
place a solid crystal of LiO in the loop, heat it with the burner and observe the flame
clean the Pt wire again
repeat for other salts
What is the experimental procedure of absorption of light by the dye in Smarties?
put each Smartie in a separate 20 mL beaker, half fill these with distilled water
set the blank on the spectrometer
fill the curvette with one of the Smartie solutions and place it in the spectrometer and measure
empty then refill the curvette with the other Smartie solution and measure in the spectrometer
What are the reactions involved in the formation of KAl(SO4)2*12H2O?
first the metal scraps of aluminum will be dissolved by a reaction with hot potassium hydroxide
Al + KOH + H2O —> K + Al(OH)4- + H2
next sulfuric acid is added, initially a white solid Al(OH)3 is formed
Al(OH)4- + H2SO4 —> Al(OH)3 + H2O + SO4
however, the Al(OH)3 undergoes further reaction
Al(OH)3 + H2O —> Al + SO4 + H2O
What are the reactions are involved in determining how much phosphate is in fertilizer?
a known mass of fertilizer will be mixed with water to dissolve the ammonium dihydrogen phosphate (the actual phosphate containing material present rather than P2O5)
excess magnesium sulfate solution is added (with ammonia to adjust the pH) to form MgNH4PO4*6H2O
this solid is isolated through filtration and weighed
How would you convert your mass of MgNH4PO4*6H2O to the equivalent mass of P2O5?
the two substances are linked by:
P2O5 (cited by the manufacturer) —> (NH4)H2PO4 (actual fertilizer) —> MgNH4PO4*6H2O (your product)
in your calculation of the equivalent mass of P2O5 you do not have to balance the complete reaction to obtain the relevant mole ratio
What is the experimental procedure for measuring the formation of KAl(SO4)2*12H2O?
cut up the aluminum scrap and clean and dry a 250 mL beaker
in the fume hood, add 50 mL of 0.5 M KOH solution to the beaker
filter particles out of the solution
acidify the solution by slowly adding 20 mL of 6M H2SO4, heat the mixture gently
What is the experimental procedure for measuring phosphorus in fertilizer?
weigh a clean and dry 150 mL beaker, then weigh 2 to 3 grams of fertilizer into it
add about 40 mL of water to the beaker
add approximately 30 mL of 0.4M MgSO4 solution to the beaker with fertilizer
extract and dry the percipiates
What is Vitamin C?
is water soluble due to formation of hydrogen bonds between its (-OH) and (C = O) groups and the (-OH) of the solvent molecules
What are the reactions involved in the titration with KIO3?
the iodate anion reacts with I- and H+ to form I2
IO3- + 5I- +6H —> 3I2 + 3H2O
once formed, I2 is reduced immediately by Vitamin C back to I-, as each I2 reacts with one C6H8O6 molecule, each IO3- that is added results in the reaction of three C6H8O6 molecules
after all the vitamin C in the sample has been consumed, the I2 (from the addition of one more iodate) reacts rapidly with I- to form the linear triiodide ion I3-
I2 + I- —> I3-
I3 - will react promptly with starch to form a blue-black starch triiodide ion complex, this color change indicates the endpoint
What are the reactions involved in the titration with NaOH?
in this titration, vitamin C reacts in a 1:1 mole ratio
How do you compare the titration results of the KIO3 and NaOH titrations?
moles of vitamin C in aliquot = 3*(moles of iodate added to reach the endpoint)
moles of acidic protons in aliquot = moles of NaOH added to reach the endpoint
What are the trends of atomic radii and metallic character on the periodic table?
atomic radii decrease left to right, increase top to bottom
metallic character decreases left to right, increases down a group
What are chemical bonding?
an ionic bond forms when metal (lose electrons easily) combines with a nonmetal (gain electrons easily)
a covalent forms when the electrons are shared by the two bonded elements
What is electronegativity?
measure of an atom’s ability to attract the bonding electron density to itself in a molecule
increases from left to right along a period, decreases down a group
bonding in a binary compound involving a metal and nonmetal to be primarily ionic if electronegativity difference is greater than approximately 2
