Chemistry Lab Exam

Question	Answer
Image: poision_symbol.JPG (image/JPG)	poisonous and infectious material causing immediate and serious effects
Image: flammable_symbol (image/jpg)	flammable and combustible material
Image: reactive_symbol (image/jpg)	dangerously reactive material
Image: infectious_symbol (image/jpg)	Poisonous and infectious material
Image: oxidizing_symbol (image/jpg)	oxidizing material
Image: other_effects_symbol.JPG (image/JPG)	Poisonous and infectious material causing other toxic effects
in the hydrate experiment blue CuSO4 was dehydrated to a white solid. what happened when water was added again and why?	the substance turned blue again, meaning the reaction was reversible and when water was added it was once again CuSO4
in part one f the iron absorbance lab, was the first calculation needed	the final concentration: this was found by taking the original stock concentration (4.27 x 10 to the power of -5) multiplyed by the volume of that solution added in each run all divided by the total volume in the volumetric flask (50 ml)
should points used for the slope of a calibration curve be close together or far apart?	far apart
in the Spectrometer determination lab what are the Y and X values on the graph	y is absorbance (no units) X is concentration of Iron (mol/L)
does absorbancy have units?	not usually but you can use AU if you wish
in part 2 of the spectrometric determination of Iron experiment how was the total iron in the well water sample calculated?	the absorbancy was measured and then, using the calibration curve (matching y value) this value was found on the graph and matched to an approximate iron concentration value (X value)
in the sepectrophotometric determination of iron experiment, before the absorbancey can be measured Iron(III) has to be reduced to Iron (II) using NH2OH. Write the balanced reaction equation.	4Fe(3+)(aq) + 2 NH2OH(aq) --> 4Fe(2+)(aq) + N2O(g) + 4 H(+)(aq) + H2O(l)
Fe2+ is then added to a weak base and is then ready for absorbance measurements. Write the balanced equation of this reaction.	Fe(2+)(aq) + 3bipy(aq) --> [Fe(bipy)3](2+)(aq)
what are the values for beers law A=eBC	A = absorbance (no units) e = molar absorptivity (mol/L x cm.) B = the path length the photons have to travel (cm.) C = the concentration of the compound in solution being measured
the the compunds of copper experiment copper solid reacts with with nitric acid to form__?	copper nitrate and nitrogen dioxide
in the compounds of copper experiment in part 1 B copper II nitrate reacts with sodium carbonate to form ___?	copper II carbonate and and carbon dioxide
in the compounds of copper experiment in part 1 C copper II carbonate is reacted with hydrochloric acid to form ___?	Copper II chloride and carbon dioxide
in the compounds of copper part 2 A experiment copper II sulfate is reacted with sodium hydroxide to form ___?	copper II hydroxide
in the compounds of copper part II B experiment copper hydroxide is heated to form ___?	copper oxide
in the compunds of copper part II C copper oxide was reached with sulfuric acid to form ___?	copper sulfate
in the compounds of copper part 1 D experiment copper chloride was reacted with aluminum metal and hydrochloric acid to form ___?	copper solid, aluminum chloride, and hydrogen gas
what are the two types of balances used in the lab?	general purpose balance and analytical balance
describe the steps to accurately measure a sample.	- zero the analytical balance -place the empty container on the analytical balance -record the mass of the container to the 0.001 grams -place empty container on the general purpose balance -zero the balance -add the approximate mass of the sample needed to the container n the balance -return the sample and container to the analytical balance -record the mass of the sample+solid and use these values to find the mass of the sample
when measuring a sample, samples are never to be measured over___	top of the analytical balance
what should you do with extra sample?	but it in the solid waste bottle NOT back in the reagent bottle
the balance is accurate to___. but it still needed to be interpreted at___.	0.003 g., +/- 0.001g.
what is the gas inlet on a Bunsen burner?	its the screw valve at the center of the base
What is the air inlets?	holes at the bottom of the barrel
what does it mean if we say a hydrate has Efflorescence?	It has a higher water vapor pressure then the atmosphere and thus will loose its water to the atmosphere and become a powder
how would you calculate the mass percent of water?	find the total mass of water by finding the difference in weight of the sample before and after heating. divide this value by the mass of the sample before heating and then multiply by 100%
What reagents used in the hydrates lab would be corrosive?	the reagents used are eithersalts, nitrates, sugars, acids or bases. In this case only the acids and bases would be corrosive. so HNO3, NaOH, and H2SO4
what happens when you heat sucrose (C12H22O11)?	the hydrogen bonds break, releasing water vapor and leaving carbon solid
After heating sucrose a black or brown solid is left behind. What is that solid?	Carbon solid
if a carbonate ion was present that substance would?	react with HNO3 to form carbon dioxide and water
if a sulfate ion was present the substance would?	react with Ba(NO3)2 to form the white solid Barium sulfate and nitrate
if a chloride anion was present the substance would?	react with AgNO3 to form white solid sliver chloride and nitrate
if a bromide anion was present the substance would?	react with AgNO3 to form silver bromide and nitrate
how do you calculate the empirical formula of a hydrate?	-find the moles of water from the mass of water lost divided by the molar mass - find the moles of the anhydrous salt -find the molar ratio by dividing the moles of water by the moles of the anhydrous salt -round to the nearest whole number and substitute for n

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	Created by jennabarnes12387 about 11 years ago