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109 Cards in this Set

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What does random error effect?
Precision
what is the name of the "curve" which demonstrates the distribution of a large set of random error values?
Distribution curve
What does systematic error effect?
Accuracy
Standard deviation
a single number that measures the width of distribution. The larger the value of this number the less precise the measurement.
How many sig figs ahould standard deviation be rounded to?
1
When are zeros significant figures?
when they are terminal zeros to the right of the decimal (14.10 has 4 sig figs). Internal zeros.
How do you determine sig figs when you multiply or divide?
there should be as many sig figs in the answer as there are in the measurement with the least amount of sig figs.
How do you determine sig figs when you add or subtract?
The answer should contain the same number of decimal places as the measurement with the least number of decimal places.
Atomic Number (Z)
The number of protons in the nucleus of an atom.
Element (X)
Substances whose atoms all have the same atomic number
Neutron
atomic partical whose mass is about equal to that of a proton but has a charge = 0.
Mass Number (A)
# of protons + # of neutrons
Nuclide Notation
A
X
z
Isotopes
Atoms with the same number of protons but different number of neutrons
How do you avoid paralax error?
by using the bottom of the meniscus to indicate all measurments
How is the delivered volume from a graduated cylinder effected when it is calibrated to contain (TC)?
the delivered volume is slightly less than the measured volume
How is the deliverd volume effected from a graduated cylinder when it is said to be calibrated to deliver (TD)?
the delivered volume is slightly greater than the measured volume.
What is the maximum measurement of volume that can be obtained from a graduated cylinder?
+/- 1 mL up to the maximum volume of the graduated cylinder.
What is a transfer pipet calibrated to?
(TD) to deliver
can in individual transfer pipet deliver multiple volumes accuratly?
NO
Steps for proper transfer pipet use:
1. Place rubber suction at mouth of pipet with dexterous hand, squeez air from bulb.
2. Insert pipet into liquid. Allow bulb to expand slowly. DO NOT ALLOW LIQUID TO ENTER BULB
3. When liquid is about 1 cm above the etched line on the pipet, remove the pipet from the liquid.
4. Dry the exterior of the pipet with tissue paper.
5. Drain excess into waste container untill the bottom of the meniscus coincides with the etched line.
6. Allow pipet to drain in to the container to be used in the experiment. Touch of any last drop.
7. DO NOT BLOW ANY REMAINING LIQUID FROM THE PIPET.
When using a transfer pipet why is it important to not allow liquid to enter the bulb?
it could cause contamination
When using a transfer pipet why are we not concerned with the remaining drops of liquid in the pipet once the it has been transfered in to the container to be used in the experiment?
b/c the pipet is calibrated to deliver (TD)
What is one of the major safety precautions that should be practiced when using a pipet?
NEVER PUT YOU MOUTH TO A PIPET
Three steps to make sure your buret is functioning properly:
1. The capillary tip should be clean and free of foreign objects.
2. If water droplets are left on the inner walls of the buret after draining it needs further cleaning (w/ hot water, detergent and a buret brush.
3. Make sure there are no leaks in the stopcock. Drops should not form in the capillary when the stopcock is completely shut.
Do teflon stop cock require lubrication?
No
Do glass stopcocks require lubrication?
Yes, to prevent leaking and to allow easy turning.
What does the volume in a buret indicate?
The amount that has been deliverd not the amount that remains.
The spacings between the lines of a buret allow you to measure to the nearest ______ mL?
0.01 mL
What are the left and right hands doing if proper technique is used with a buret?
The left hand operates the stopcock. The right hand is swirling the flask
How far do you open the gas outlet when using a bunsen burner?
You completely open the gas valve.
How far do you open the gas inlet valve when lighting a bunsen burner?
You open the inlet valve halfway.
How do you approach a bunsen burner with a match when igniting it?
Bring the match from the side to the top of the burner.
How many inches high should the flame of a bunsen burner be?
The flame should be about 4 inches high.
What color should the flame of a bunsen burner be?
The flame should be a luminous yellow. Two concentric cones will form. The outer cone will be faintly colored while the inner cone will be blue.
Where is the hottest part of a flame on a bunsen burner?
the tip of the blue inner cone of the flame.
What equipment is needed for gravity filtration?
conical filter with a hollow stem, a glass stirring rod(w/w/o a rubber policeman), filter paper, a stand, a iron ring, a clay triangle and a beaker/flask to catch the liquid.
What is a rubber policeman used for?
to remove precipitates from the walls of a beaker or a flask.
Where should a mixture be poured (decanted) when using gravity filtration?
the mixture should be decanted along the stirring rod into the conical filter funnel containing filtration paper.
How is any remaining solid in the beaker or flask transfered to the paper in gravity filtration?
Rise with a stream of distilled water from a plastic wash bottle.
What kind of transfer is achieved with gravity filtration yet rarely achieved with suction filtration?
A quantitative transfer.
What equipment is used in suction filtration?
a Buchner funnel, suction flask, a rubber stopper/ring, a glass stirring rod, heavy rubber tubing, a water aspirator, a stand, a iron ring, a clay triangle and a beaker/flask to catch the liquid.
A solid is trasfered and washed with distilled water. What next step happens in suction filtration and not in gravity filtration?
The solid is then sucked dry
5 important precautions when using reagents:
1. NEVER put anything in a reagent bottle; only remove reagents from their bottles.
2. Take only the amount needed to minimize waste.
3. Re-cap reagents at once.
4. DO NOT remove reagent bottles from the reagent area.
5. Keep instrument and reagent area clear of spilled chemicals
What are the only items that should be on the counter or near the experiment, other than equipment, during lab?
a data sheet and pen
Sign that a chemical reaction has taken place.
1. formation of a solid or a gas
2. color change
3. heating or cooling
NaCl
sodium chloride
NaI
sodium iodide
Na2CO4
sodium carbonate
Na2HPO4
sodium hydrogen phosphate
Na2SO4
sodium sulfate
HNO3
nitric acid
[Ba(NO3)2]
barium nitrate
AgNO3
silver nitrate
thymol blue
acid indicator
what is a good indication that a gases are evolving?
bubbles form and move upward through the solution.
What is a precipitate?
a solid
what saftey precaution should be used when handling HNO3 (nitric acid)?
This solution may cause chemical burns. It may ruin clothing. If this solution is spilled wash the contaminated area thoroughly with tap water abd report the incident to your lab instructor. If it has spilled on you, you may require further treatment.
What solution is used in testing for gas evolution in experiment 1A?
HNO3 nitric acid (5 drops)
How did we dissolve the unknown compund in experiment 1A?
Place a pea-sized amount of the unknown compound in 400 mL beaker. Add 200 mL of distilled water. Swirl beaker untill solid is dissolved.
NH3
ammonia
What saftey precautions should be used with NH3 (ammonia)?
This solution may cause chemical burns. It may ruin your clothing. If the solution is spilled, wash the contaminated area thoroughly. Report the incident to your lab instructor. If the solution spill was on you you may require further attention.
why did we shake the test tubes containg our compounds after adding 5 drops of the solution Ba(NO3)2 to each of them (1A)?
to achieve homogenity
after adding Ba(NO3)2 to the test tubes what observations should have been made?
Examine for precipitates and the color of the precipitates.
What safety precautions should be used after using solutions containg barium?
When using solutions with this element in them make sure to wash your hands thoroughly. This element is poisonous.
When we added HNO3 to the test tubes containg solutions that formed precipitates (after adding Ba(NO3)2) what were we looking for (1A)?
We were looking for which precipitates had dissolved.
In each test tube containing the known/unknown compounds 5 drops of AgNO3 were added. What was observed?
The formation of precipitates was observed.
Each test tube contains known/unknown compounds + AgNO3 and has also formed a precipitate. HNO3 has now been added untill each solution has turned pink (only to those that did not turn pink with the blue litmus paper). What observations should be made at this point? (1A)
If the precipitates have dissolved.
Which compound in experiment 1A might behave differntly (due to differences in concentrations) when tested with AgNO3?
Na2CO3
Chromotography
a name given to a group of similar separation techniques that depend on how fast a substance moves, in a steam of gas of liquid, past a stationary phase to which the substance may be slightly attracted.
what served as the stationary phase in paper chromotography?
paper
What served as the mobile phase in paper chromotography?
liquid
what phenomenon causes liquid to flow up the filter paper in chromotography?
capillary action
What two affinities are in competition in regards to the components being tested in paper chromotography?
the componets affinity for the paper and for the liquid are competitive.
Rf value
=(distance traveled by spot)/(distance traveled by liquid)
What is the Rf value a measurement of?
The components competitive affinities for the stationary and mobile phase.
CoCl2
cobalt(II) chloride
NiCl2
nickle(II) chloride
CuCl2
copper(II) chloride
FeCl3
iron(II) chloride
What was used as mobile phase in experiment 1B?
a mixture of the aqueous solution HCl (hydrochloric acid) and either acetone or 2-butanone.
What precautions should be used with acetone and 2-butanone?
These solutions are volatile and flamible. No flames will be allowed when using them.
What solutions are sprayed on the paper when the chromotography experiment is completed?
NH3 (ammonia) and Na2S (sodium sulfide)
What does Na2S react with inthe mobile phase? what is formed?
HCl. NH4Cl (ammonium chloride)
NH4Cl
ammonium chloride
What equipment is needed in paper chromotography
filter paper, small scrap of same paper, 5 capillary tubes, 4 test tubes, a piece of clear plastic film, a rubber band,, an 800 mL beaker
what is the maximum diameter of an acceptable spot in paper chromotography?
0.5 cm
Where should the 2 cm line be when the filter paper is placed into the mobile phase?
the line should be above the liquid or close to it.
How close to the top of the stationary phase should you allow the mobile phase to ascend in paper chromotography?
within 2-3 cm of the top of the stationary phase.
what methods can be used in drying the stationary phase?
holding it briefly over a heat lamp or by waving it gently in the air.
What precautions should be used with sodium sulfide and its reaction product with water?
This solution is toxic and should not be tasted or inhaled. an efficient hood must be used.
After NH3 and Na2S have been sprayed on the stationary phase in the final step of chromotography, what should be visible?
a dark spot representing each substance.
The vertical distance traveled by each spot should be measured to the nearest _____ of a cm.
tenth
Why is a pencil used and not a pen to draw lines on the filtration paper in the chromotography experiment?
Because the ink will have and affinity for the mobile phase and will act much like the compounds to be observed. This will obviously effect the outcome of the experiment.
If the distilled water in the experiment has passed through iron pipes this may cause an impurity in the result. What is an indication that an impurity is present?
horizontal streaking rather than a spot.
accuracy
the relationship between a measured value and its true value.
what value must be known to determine a measurments accuracy?
the true value of the quantity
What type of curve can be used to describe the results of random errors?
a bell shaped curve
What point on a bell shape curve corresponds to the average or mean value?
the maximum height of the curve
precision
is determined by examining the closeness of measured values to eachother.
standard deviation
= the sum of {x(i) - x(bar)}/(n-1)

x(i): a particular value of measurement

x(bar): the mean (average) value.

n: the number of measurements
Why is tissue paper used when handling flasks and beakers to be used when taking measurements of mass?
tissue paper is used in handling because the oils on your fingers can be detected by some balances.
which elements/compounds were examined in the experiment involving mass spectrometry?
mercury, hydrogen chloride, hydrogen bromide and neon.
how does determining the atomic weight of a element take into account its naturally occurring isotopes?
it the weighted average of the exact masses of it naturally occuring isotopes.
how would the atomic mass of any element Y consisting of isotopes Ya and Yb be calculated?
atomic weight of Y =
[(exact mass of Ya) x (fractional abundance of Ya)]+[(exact mass of Yb) x (fractional abundance of Yb)]
what is collected at the different collection points in a mass spectrometer?
ions with the same mass
mass spectrum
a graph representing the total number of of counts for each ion recorded by a mass spectrometer.
What do the numbers along the horizontal axis of a mass spectrum correspond to?
the mass number of different isotopes of an element.
What does the vertical axis of a mass spectrum correspond to?
the relative abundance of differents isotopes of an element recorded by the mass spectrometer.