Chemistry Lab Cheat Sheet PDF

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Molecular Weight of a Gas (MW= mRT/PV, K=c-273, R=6.24x104, P=mmHg) 1.) Fill the Plastic tub with room temperature water 2.) Get a Stand from the windowsill 3.) Attach 3-pronged clamp to stand using a clamp holder (3rd drawer down) 4.) Submerge 50 mL graduated cylinder (top drawer) in the tub so that cylinder fills with water 5.) Invert cylinder. Use clamp to hold in place 6.) Discharging gas: Attach the correct diameter plastic tube to the gas opening on the top of the lighter (use correct tube!) 7.) Insert the other end of the tube under the mouth of a 50 mL graduated cylinder under the water. *Weigh lighter before and after to find the mass of gas discharged 8.) Carefully release the gas in the lighter and collect it in the cylinder 9.) After the gas is dispensed, reweigh the lighter 10.) Adjust the height of the cylinder so that the level of water inside and out are the same 11.) Record volume 12) Use thermometer in top drawer to record temperature 13.) Record atmospheric pressure (station pressure) 14.) Calculate apparent molecular weight of gas. Repeat trials Prepare a salt solution at a requested concentration and measure the density of the solution. (M1V1=M2V2, Molarity = moles of solute/ liter of solution) Volumetric Pipette Important Information: 1.) Make sure pipette is clean by rinsing with DI water 2.) Blow out left over liquid 3.) Rinse pipette 3 times with solution 4.) Draw up aliquot and wipe the tip 5.) Set the meniscus 6.) Deliver aliquot with pipette vertical and flask at 30 angle Density of a Liquid with Volumetric Pipette (Check for TD) 1.) Measure the mass of a 150 mL beaker using an analytical balance. Record and write full number of digits. Use the same balance for all measurements. 2.) Use Volumetric pipette to add a 10 mL portion of DI water to the beaker 3.) Measure mass of Beaker and water 4.) Calculate the mass difference 5.) Use mass difference to calculate density *Round density calculation to have +1 sig fig than mass, disregard data if mistake is made 6.) Perform 3 or more replicate density determinations 7.) Record information printed on pipette Method Using a 10 mL Graduated Cylinder (Check for TC) 1.) Weigh Graduated Cylinder 2.) Add Water (9-10mL) 3.) Shake water out of cylinder between density determinations You have a hydrate of unknown composition. Heat the sample to a constant weight. Example: KAl(SO4)2•12H2O(s) → KAl(SO4)2(s) + 12H2O(g) 1 mol Alum → 12 mol H2O 1 𝑚𝑜𝑙 𝐴𝑙𝑢𝑚

((.23g Alum)(474.28 𝑔 𝐴𝑙𝑢𝑚)𝑥 (

12 𝑚𝑜𝑙 𝐻2𝑂

1 𝑚𝑜𝑙 𝐴𝑙𝑢𝑚

)𝑥 (

18.015𝑔 𝐻20

1 𝑚𝑜𝑙 𝐻2𝑂

.104835 𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑚𝑎𝑠𝑠 .104835/.23 = 45.58% theoretical percent lost .11/.23 = .478261 or 47.83% PERCENT ERROR= 𝑒𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙−𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙

)=

Given an unknown solution Given an unknown solution containing copper (II) and the correct calibration curve, determine the concentration of the sample. [Cu(H2O)6]2+ (aq) + NH3(aq) → [Cu(NH3)4(H2O)2]2+(aq) + water, aquamarine → dark blue 1.) Use a graduated cylinder to transfer 25 mL of this solution into a 50 mL volumetric flask 2.) Then add 10 mL of a dilute ammonia solution (2.8 M). The ammonia will have a pump on top of the bottle set to 10 mL 3.) Mix well, fill the volumetric flask to the line with DI water and mix again EXAMPLE: y y=0.0007x - 0.0062; Abs=0.0007[conc] - 0.0062 [Spectrometer sample conc] =(abs+.0062)/.000714 Filtrate conc = [spec sample conc * 2 (the dilution factor) Evaluate the effectiveness of a water filter (like a Britta Filter) in removing copper(II) from a water sample. You will be given a calibration curve for the copper-ammonia complex. % Retention = (original conc-final conc)/original conc x 100 % retention = (800-filtrate concentration)/800 x 100) Distinguish between samples of alum, potassium sulfate, aluminum nitrate, barium nitrate, and potassium hydroxide What happens when you raise the pH? 1.) Put some of your alum test solution into a small test tube to a depth of about one centimeter 2.) Raise the pH using the 1M potassium hydroxide solution provided 3,) Add test tube solution dropwise and mix thoroughly. Continue addition until no further changes Does your product contain aluminum ions? 1.) Use aluminum which reacts with aluminum ions to form a colored compound 2.) Add Alum/whatever solution to a clean small test tub 3.) Add aluminom, look for red colored compound Does your product contain sulfate ions? 1.) Barium chloride reacts with sulfate ions to give a white precipitate 2.) Add Bacl to pure alum solution n test tube. Observe to see if white precipitate forms Na2SO4(aq) + BaCl2 = 2NaCl(aq) + BaSO4(s) KAl(SO4)2 * 12H2O(aq) + 2BaCl2 (aq) = 2BaSO4(s) + KCl(aq) + AlCl3(aq) + 12H2O(l)

1.) Set a hot plate to 300 degrees (measure temperature with the non-contact thermometer gun, get surface between 280-400 C) 2.) Get vial from glass rack at sink 3.) Weigh the empty vial and record this mass in your notebook. 4.) Place between .2 and .4 grams of your crystals into a vial. Remove the vial from the balance pan before you add a chemical to it! 5.) Take the difference between the two readings to calculate the mass of alum 6.) Put vial on hot plate. When nothing interesting happens, remove vial. Pick up a hot vial using a metal test tube holder. Allow to cool to room temperature and then reweigh it. Repeat this heating procedure until you get two successive weights that match

Given an unknown solid acid, determine the neutralization equivalent. Standardize the NaOH Solution Titrate with KHP 1.) Titrate a sample that is between .25 and .35 g of the weak acid potassium hydrogen phthalate (chemical formula KC8H5O4 + NaOH →KNAC6H4O4 + H2O molecular weight of KHP = 204.2g/mol 2.) Start with a clean but not necessarily dry mass burette, found in bottom drawer. Rinse the burette with 3 small portions (about 2 mL) of the base solution 3.) Fill the burette with NaOH solution. Do not get close to the maximum fill line marked on the bottle. 4.) Put 250 mL erlemyer flask on balance, use tare button 5.) Weigh .25-.35 g of KHP 4.) Add DI water up to 50 mL line on the flask and 3 drops of phenolphthalein 5.) Add a magnetic stir bar by sliding it down the flask 6.) Record initial weight of burette using top loading balance 7.) Add NaOH. As you near the end point of the titration the pink color will persist for longer. Slow NaOH at the end point. Add the titrant to the solution dropwise from the burette’s pipette until the first hint of pink persists for 30 seconds. Repeat this titration until you have three concentrations that agree with 1 percent Neutralization Equivalent of an Unknown Acid: 1.) Measure between .10 and .35 g of your unknown acid, answer must have four significang figures 𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑁𝑎𝑂𝐻 = 𝑚𝑜𝑙/𝑘𝑔 1 𝑔𝑟𝑎𝑚𝑠 𝑜𝑓 𝐾𝐻𝑃(.3119) 1 𝑚𝑜𝑙 𝑜𝑓 𝑁𝑎𝑂𝐻 𝑥 𝑥 = 1 𝑚𝑜𝑙 𝑜𝑓 𝐾𝐻𝑃 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑁𝑎𝑂𝐻 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑖𝑛 𝑘𝑔 = (. 10881 − .09311)𝑘𝑔 𝑀𝑊 𝑜𝑓 𝐾𝐻𝑃(204.2) Neutralization Equivalent (NE) = grams of sample/moles of OH1 1 NE= 𝑔𝑟𝑎𝑚𝑠 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒(.2814) 𝑥 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑁𝑎𝑂𝐻 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑖𝑛 𝑘𝑔(.09310−.08397)

Prepare a 1:10 dilution and a 1:100 solution. Measure the absorbance Plot absorbance vs concentration. Determine the extinction coefficient of the solute. 1:10-take 15mL from hood-transfer 5 mL to 50 mL vol. Flask, fill flask to line with solvent, cap flask and invert 10x1:100-same as last except .5mL of solutePlug into Beer Lambert Law for extinction coefficient a=log10(Io/It)==ecl, e=ext co(slope of abs vs conc), l=length light traveled, Transmittance of the surface of a material is the effectiveness in tramsmitting radiant energy , T=It/Io OR initial light intensity/light intensity after passing through absorbance • • •

• • • •

a. Dispensing Pumps: set to a specific amount, pull up and push down all the way b. Funnel: used in a gravity filtration with a wastepaper c. Vacuum filtration: attach vacuum hose to flask and faucet, clamp filter flask in place. Place a stopper and Buchner funnel on top of the flask. Place filter paper on top and moisten filter paper with solution. Pour the whole solution onto filter paper. Turn on vacuum for x minutes. Bromothymyl Blue, yellow=acid, blue=basic Ca(s) + 2H2O(l) = H2(g) + Ca(OH)2(s) calcium is oxidized and hydrogen water is reduced, steam cloudy heat Ca(OH)2(s) + 2HCl(aq) = CaCl2(aq) + 2H2O(l) Precipitate dissolves clears up, add sodium alginate Ca(s) + 2HCl(aq) = H2(g) + CaCl2(aq)

T-test = abs value of the calculated tcritical value=sig difference, rejct hypothesis that two data sets are different Jobs Plot= mole fraction/stochiometric point Accuracy=close to true value, Precision=degree of reproducibility

𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑡ℎ𝑒 𝑁𝑎𝑂𝐻 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛

synthesize lithium chloride as an approximately 0.1 M solution. Use the same method to prepare lithium chloride as calcium chloride. 1.) Synthesize LiCl Solution Li(s) + 2H2O → Li(OH)2(s) + H2(g) Li (OH)2(s) + 2HCl(aq) → LiCl2(aq) + 2H2O(l) Li(s)+ 2HCl(aq) → LiCl2(aq) .01725 g of Li 2.) Use 250 mL beaker to measure volume and perform synthesis 3.) Put a magnetic stirbar into a 250 mL beaker and add 70 mL of DI water 4.) Weigh out .01725 g of Li metal 5.) Calculate and record actual mass you weigh. Use top loading balance that measures to 2 decimal places 5,) Add Li gradually to the stirring water. steam, cloudy, heat 6.) Measure the final temperature after Li is complete 7.) Add HCl with plastic transfer pipette until solution clears up and all the precipitate has dissolved Synth of Alum • 2Al(s) + 2KOH(aq)+ 6H2O(l) → 2KAl(OH)4(aq) + 3H2(g) • Al is oxidized, H2O or OH- is reduced • KAl(OH)4(aq) + 2H2SO4(aq) + 8H2O(l) →KAl(SO4)2*12H2O (s) • Overall: 2Al(s) + 2KOH(aq) + 22H2O(l) + 4H2SO4(aq) -> 2{KAl(SO4)2*12H2O}(s) + 3H2(g) • At first, when I added KOH, the solution became cloudy. Towards the end, the solution cleared up. When the solution was cloudy, this is the reaction that occurred: KAl(SO4)2 * 12H2O(aq) + 3KOH(aq) = Al(OH)3(s) + 2K2SO4(aq) + 12H2O(l) • When the solution cleared up with base, the solid precipitate which was Al(OH)3 became KAl(OH)4(aq) which is an aqueous solution, and therefore, was clear : Al(OH)3(s) + KOH =...