chem lab final review
The mass before soaking of a potato disk is 1.801 g . After soaking it is 1.530 g. What is the percent change?
% change=(final- original)/original x 100 % (1.530- 1.801) / 1.801 x 100% =15.047196% 3 sigfigs so... =15.0%
what is the percent yield of copper metal if you recovered 1.4774 g Cu and you theoretically should have had 1.428 g?
% yield = |actual/theoretic| x 100% = | 1.474/1.428 | x 100% =103.2212885% =4 sigfigs so =103.2%
How would you make a solution for a 35 mL of a 0.90% w/v NaCl solution.
(0.90 g NaCl/ 100 mL solution x 35 mL solution=0.315 g NaCl =0.32 g NaCl) You would add 0.32 g NaCl to a graduated cylinder and then add water up to 35 mL.
atm=0.9775, volume=0.0388 L, moles=0.0016, temp=294 K...what is the gas constant R?
(0.9775)(0.0388)/(0.0016)(294)=0.080627159 L-atm/mol-K 2 sigfigs-->0.081 L-atm/mol-K
atm=0.9775, volume=0.0461 L, moles=0.0018, temp=294 K...what is the gas constant R?
(0.9775)(0.0461)/(0.0018)(294)= 0.0851525888 L-atm/mol-K 2 sigfigs--> 0.085 L-atm/mol-K
volume of cylinder= ?
(pi)(r^2)/h or (pi) (d/2) ^2 h
what is the molar mass of Cu ^ 0?
(see periodic table) = 63.546 g/mole =4 sigfigs--> 63.54 g/mole Cu^0
when heating the salt, sand, ammonium chloride sample what are the white vapors escaping off the top? what is this process called?
(white vapors escaping off the top is ammonium chloride escaping into the atmosphere) process=sublimation
what is the precision of a 100mL graduated cylinder?
+/- 0.1 mL
Describe what back titration is in the antacids:evaluation through acid base titration lab
...where excess acid is added to the antacid so the antacid neutralizes what it can and then a base is added to calculate how much acid was not neutralized by the antacid. the difference b/w original quantity of acid and amount of unneutralized acid will tell how much acid was neutralized.
freezing point of water
0.0 degrees celsius or 273.15 kelvin
Given the number of moles of CuCl2 dissolved in solution (0.02247 moles CuCl2), how many moles of Cu ^2+ were INITIALLY in solution? CuCl2(aq) --> Cu ^2+ (aq) + 2 Cl -(aq)
0.02247 moles CuCl2 X (1 mole Cu ^2+)/ (1 mole CuCl2) = 0.02247 moles Cu ^2+ 1:1 ratio because of law of conservation of mass!
If 0.0416 g of Mg are reacted with excess HCl, how many moles of H2 will be formed? Mg+2HCl-->MgCl2+H2
0.0416 g Mg/24.31 g/mol Mg X 1 mole H2/1mole Mg=0.0171 mole H2
what is R
0.0821
calculate the mass of NaCl needed to prepare a 35 mL of a 0.90% w/v NaCl solution.
0.90 g NaCl/ 100 mL solution x 35 mL solution=0.315 g NaCl =0.32 g NaCl
describe the procedures for : measuring density & temperature of salt water lab
1.choose a clean 250 mL beaker and measure & record its mass 2. add 4-6 g (4 small scoops) of NaCl (sodium chloride) to the beaker and record the mass of the beaker + NaCl 3. calculate the EXACT mass of NaCl added to the beaker (beaker+NaCl mass - mass of beaker = mass of NaCl alone) 4. add DI water & dissolve the salt. once dissolved, add a small shoveful of ice. stir 4 mins w/ thermometer & record lowest temperature (if ALL ice melts, add more) 5. use a 10 mL graduated cylinder to obtain 7-9 mL of this salty ice water(no ice). record the volume to the correct precision of instrument. 6. obtain mass of erlenmeyer flask 7.pour measured water from step 5 into erlenmeyer flask of step 6 & record new mass. 8. calculate the EXACT mass of the salty ice water (saltyicewater+erlenmeyer flask mass - erlenmeyer flask mass = salty ice water mass) 9. calculate the density of the salty ice water (Density= mass/ volume)
describe the procedure of the copper lab
1.get CuCl2 (>3g) on weighboat & record its mass to the precision of the instrument 2.place sample in 250 mL beaker 3. place residual CuCl2 from weighboat to beaker using DI water, adding about 60 mL of water to the beaker. Stir until CuCl2 is dissolved. Solution should be BLUE/BLUE-GREEN, characteristic of Cu ^2+ ions in water. 4. get aluminum wire with mass of about 1.5 grams. 5. twist 1 end of Al wire into a coil & immerse coiled end in copper solution 6. observe reaction.over time, blue will fade as Al reacts and Cu metal will accumulate on Al's surface. Shake wire 24/7, knocking against beaker's sides to loosen Cu that accumulates on wire. Reaction is complete when the blue is gone and aluminum wire has nor more copper accumulation (20-30 mins) 7.once done, remove Al wire & shake/tap so all Cu falls back into beaker. If Al falls/wire breaks in beaker, impure copper (Cu & Al mix) is isolated so be sure ONLY Cu is in beaker. Use DI water over beaker to remove Cu, Scrape Cu off with rubber side of stir rod. 8. Discard Al appropriately 9. grab filter paper, print drawer # on it. record mass of filter paper w/ watchglass to instrument's precision. 10. assemble vacuum filtration apparatus 11. put labeled filter paper, label side down, in Buchner funnel and isolate copper by vacuum filtration. Rinse Cu in beaker into buchner funnel using DI water. 12. once copper is tranferred, washed copper with DI water (20 mL each time) so any non-seen salts are washed away 13. wash same filtrate with 20 mL acetone... acetone will wash away the water and evaporate quicker, hastening copper drying. Let vacuum dry copper in funnel 2 mins. 14. transfer filter paper with copper to watchglass ...filter paper should be label side up now.place watchglass in oven for 10 mins. allow to cool for 10 mins. record its mass. 15. calculate % yield of copper found.
The mass of a flask is 135.469 g. The mass of the NaCl and flask is 137.014 g. So what is the mass of NaCl?
137.014 g mass of NaCl and flask - 135.469 g mass of flask ----------------------------------------------- 1.545 g mass of NaCl
If your first voume is 90.1 mL and your total volume is 143.2 mL, what was the 2nd volume?
143.2 mL- 90.1 mL= 53.1 mL
Mass of erlenmeyer flask and ice water is 150.438 g. Mass of erlenmeyer flask is 142.848 g. What is the mass of the ice water?
150.438g - 142.848g = 7.590 g
Mass of erlenmeyer flask is 143.142 g. Mass of flask and salty ice water is 151.649 g. What is the mass of salty ice water?
151.649 g - 143.142 g = 8.507 g
How many moles of copper metal (Cu^0) do you expect to be formed if there were 0.02247 moles CuCl2 formed?
1:1 ratio, so 0.02247 moles copper should be formed
A bottle of Publix generic brand antacids is $2.99 with 150 50 mg tablets. what is the cents per tablet?
1st divide 150/2 because the tablets need to be 1000 mg. then 299 cents/75 tablets=4.0 cents/tablets
since you always use a weighboat to measure a substance's mass you need to exclude the weighboat's mass to get just the substance's mass. explain how you can do this.
1st way to do this: tare (set it to zero) the balance w/ empty pan & place empty weighboat on it. gently slide balance doors shut. record weighboat's mass. then subtract the weighboat's mass from the weighboat+substance's mass to get the mass of the substance alone (weighboat+substance mass - weighboat mass = substance mass) 2nd way to do this: place empty weighboat on balance & press "tare". record mass reading with weighboat+substance... no subtraction needed
The original mass of the salt, sand, NH4Cl mix sample was 2.894 g. The lowest mass obtained from sublimating NH4Cl is 2.815 g. What is the mass of ammonium chloride that sublimed into the air?
2.894 g mass of sample - 2.815 g lowest mass obtained ---------------------------------- 0.079 g ammonium chloride sublimated
calculate the mass of NaCl needed to prepare 35 mL of a 20.0 % w/v NaCl solution
20.0 g NaCl/100 mL solution x 35 mL solution = 7 g NaCl =7.0 g NaCl
water density = 1.00 g/mL... so if you have 20.0 g of water, what is the volume?
20.0 mL water
Mass of a weighboat is 2.806 g. Mass of metal and weighboat is 25.777 g. What is the mass of the metal?
25.777g - 2.806 g = 22.971 g
mass of filter paper & watchglass=26.504 g. mass of filter paper, watchglass & copper=27.978 g. what is the mass of copper recovered?
27.978g-26.504g=1.474 g Cu
the mass of the evaporating dish is 47.615 g. the mass of the evap dish and sample mix of salt, sand, and ammonium chloride is 50.509 g. What is the mass of the sample mix?
50.509 g - 47.615 g = 2.894 g
If the % mass of ammonium chloride = 2.7%, sand=58.57%, and salt=53.39%, what is the sum of the % masses?
58.57+2.7+53.39=114.66... one place past decimal, so 114.7%
The ___ lab involves the law of conservation of mass which basically means matter cannot be created nor destroyed-so the amount of a substance that is started with should not change despite being converted into another substance.
COPPER
In reaction with Aluminum metal the copper II ion will turn into _____
Cu ^ 0, metallic copper
The mass of the filter paper and watchglass is 96.347 g. The mass of filter paper, watchglass, and dried sand is 98.042, So what is the mass of the sand alone?
98.042 g mass of filter paper, watchglass, dried sand - 96.347 g mass of filter paper and watchglass --------------------------------------------------------------- 1.695 g mass of dried sand
The temperature is 21.0 degrees celsius. Convert this to Kelvin.
K=C+273 21.0 degrees celsius +273= 294 Kelvin
how can you find Molarity?
Molarity=moles/Liters
why should you NEVER measure the mass of anything that is hot?
because it will result in artificially low masses
you know you have reached the end point during the antacids:acid base titration lab when the bromophenol turns ___
blue/bluish purple
where is the shower?
by eyewash fountain by white board
The moles of Mg reacted was 0.0016 moles Mg. How many moles of H2 were formed? (see below) Mg + 2 HCl-->MgCl2 + H2
There's a 1:1 ratio of Mg to H2 so... 0.0016 mole Mg x (1 mole H2)/(1 mole Mg) =0.0016 mole H2
The moles of Mg reacted was 0.0018 moles Mg. How many moles of H2 were formed? (see below) Mg + 2 HCl-->MgCl2 + H2
There's a 1:1 ratio of Mg to H2 so... 0.0018 mole Mg x (1 mole H2)/(1 mole Mg) =0.0018 mole H2
what is the role of acetone during the copper lab?
acetone will wash away the water and evaporate quicker, hastening copper drying.
describe reasons for % error in ideal gas law lab
air may have entered the eudiometer before H2 was produced if the stopper wasnt in tight enough. H2 may have escaped if not airtight. we may have read meniscus wrong.
what is the average R if trial 1:0.085 and trial 2:0.081?
average=( trial 1 + trial 2)/2 = (0.085+0.081)/2 =0.083 L-atm/mol-K
reactive metals react with aqueous acid to produce ___ & ___
hydrogen gas & the metal salt
solution with greater osmolarity/concentration?
hypertonic
solution with lesser osmolarity/concentration?
hypotonic
if there's a persistent GREEN color in your solution during the copper lab, what does this mean?
incomplete reaction! ...reason for theoretical yield not equaling same amount as CuCl2
excess moisture in the copper lab can ___ the mass
increase
the # of sigfigs of the calculated volume should be ____ as the uncertainty of the distances decreases
increases
solution with same concentration/osmolarity?
isotonic
of the 3 solutions used in the osmosis potato lab, which was isotonic? hypertonic? hypotonic?
isotonic=0.9 % w/v NaCl hypertonic= 20% w/v NaCl hypotonic= plain DI water
What is the purpose of the equalization chamber?
it guarantees the pressure of H2 and water vapor in the eudiometer will be the same as the atmospheric pressure
Likes dissolve ____ in solubility rules f.e. NaCl & KNO3 (potassium nitrate) are soluble in polar solvents like water.... whereas NaCl could not dissolve in non-polar gasoline
likes
Aluminum atoms in the wire ____ electrons and are thus oxidized. Al ^0 (s)--> Al ^3+ (aq) + 3 e-
lose!
if your oxidized, you have ___ e-
lost
hypotonic have ___ solute concentrations, so they are swollen
low
the gas bubble formed in the eudiometer during the ideal gas law is equal to what?
the total Pbar
if you do not remove the flask as soon as salt crystals appear when you are evaporating the water from the salt what kind of experimental error will occur?
your mass will be increased b/c the salt crystals may trap water inside them
how do you calculate % error?
|(accepted-experimental)/accepted|X 100%
explain why and where the water vapor was subtracted from. where did the water vapor pressure come from?
since H2 was produced over water, some water vapor is mixed om with the hydrogen, so the total pressure of H2 and H2O will be the same as the external atmospheric pressure. thus you have to subtract the water vapor pressure from pbar to get pH2
to separate the ammonium chloride NH4Cl from the sand, salt, ammonium chloride mix, what physical means did you use? what did it look like?
sublimation (from solid to gas); looked like white vapors escaping into atmosphere
if you are boiling the salt water on the hotplate and notice the steam coming off is more dense than water vapor, what could that indicate (in separation of a mixture lab)?
that ammonium chloride is also coming off... which means you did not do enough trials to ensure the ammonium chloride had sublimated earlier in the experiment
what is the proper clothing/attire for chem lab?
-full covering shoes & socks -long pants/jeans/skirts below mid calf -NO tights, tank tops, sandals/flipflops, shorts/short skirts -long hair tied up -shirts must 100% cover shoulders -rule of thumb: put arms by sides & look down, if any naked skin-cover it up
Find moles of Mg reacted if the mass of Mg is 0.038 g.
-to find moles when you have grams only: use single flux capacitor!! -to go from grams Mg to moles Mg you need to find the molar mass of Mg using the periodic table... it is 24.31 g/mol Mg... so: 0.038 g Mg x (1 mole Mg / 24.31 g Mg) = 0.0015631427 moles Mg we have 2 sigfigs so it is 0.0016 moles Mg
Find moles of Mg reacted if the mass of Mg is 0.043 g.
-to find moles when you have grams only: use single flux capacitor!! -to go from grams Mg to moles Mg you need to find the molar mass of Mg using the periodic table... it is 24.31 g/mol Mg... so: 0.043 g Mg x (1 mole Mg/ 24.31 g Mg) = 0.0017688194 moles Mg we have 2 sigfigs so it is 0.0018 moles Mg
760 mmHg= ? atm
1
The pressure of H2 is 742.9 mmHg. what is the pressure of H2 in atmospheres?
1 atm= 760.0 mmHg, so: 742.9 mmHg x (1 atm/760.0 mmHg)=0.9775 atm
convert 0.01070 m^3 into L
1 m^3= 1000 L 0.01070 m^3 X (1000 L / 1 m^3) = 10.70 L
describe lab procedures for using a balance
1. NEVER add a substance directly to a container on the balance. once you have the container's mass, remove it from the balance, set in on counter, & add substance. 2. return container to the balance for measurement. to add more substance, repeat step 1. 3. if too much substance was added, do NOT return it to original container b/c contaminants stock bottle for later students. excess should be discarded in appropriate waste location 4. if chemical is spilt on balance or counter, clean it up & dispose in appropriate waste container
describe procedure for the osmosis potato lab
1. cut 3 potato disks (2-3 cm diameter & 0.5-1 cm in height) 2. measure the diameter and height to the nearest 0.01 cm. place each on a paper towel labeled A, B, C. mark each disk where you made the measurements 3. record the texture of each disk 4. measure the mass of each disk 5. place disk A in a beaker and add 20% w/v NaCl solution until the disk is completely covered. 6. place disk B in a new beaker & cover w/ 0.9 % w/v NaCl solution 7. In a 3rd beaker cover disk C with DI water 8. let potato slices soak 45 mins ensuring disks remained covered the whole time...use glass stirring rods to hold under 9. remove potato slices &pat dry w/ paper towel. 10. record new textures of each disk. 11. measure diameter & height if each to nearest 0.01 cm 12. measure the mass of each.
describe the procedures of the anatacids: acid base titration lab
1. get one antacid tablet (1000 mg CaCO3) & record its mass 2. record antacid bottle price and number of tablets. calculate price per tablet. 3. put tablet in 250 mL erlenmeyer flask with about 30 mL water (by adding water, number of moles of acid / base is NOT changed) 4. use stir rod to crush tablet so it dissolves 5. pour about 35 mL of HCl solution into a small beaker. record molarity from bottle. 6. use transfer pipet & pipet bulb to suction a bit more than 25.00 mL of acid into transfer pipet. put finger on top end of pipet and wiggle until volume reaches calibration pt. transfer 25.00mL to erlenmeyer flask by placing tip in flask and releasing finger...do NOT blow remainder! 7. let antacid react while stirring for 10 min 8.rinse a clean buret 2 times with a small NaOH soln 9. close stopcock and fill buret with NaOH soln ensuring tip is full of liquid by opening and closing stopcock to fill tip....drain extra into liquid waste 10. hold a white card behind meniscus and read intial volume NaOH soln in buret to nearest 0.01 mL 11. add 8-10 drops of bromophenol blue indicator to flask. if blue/green talk to Professor. if yellow, proceed! 12. open stop cock and begin titration of antacid soln with constant swirling of receiving flask. 13. when getting close to equivalence point, you'll see bluish-purple flashes. when you do, slow down delivery of NaOH from buret (otherwise you'll overshoot the endpt giving a false result of amount of NaOH needed to use up all HCl)... at end of titration, only add 1 drop of NaOH at a time 14. @ end point, the bluish purple color should remain. find final volume reading on buret and record to nearest 0.01 mL 15. repeat steps 1-14 for a different antacid brand
describe the lab procedure for: density of an unknown lab
1. obtain an unknown metal from the hood and record its code 2. accurately measure and record the mass of the weighboat 3. add b/w 20-25 g of unknown metal to the weighboat & record its mass. calculate the exact mass of the metal (metal+weighboat mass - mass of weighboat = mass of metal) 4. add about 50 mL of water to a 100 mL graduated cylinder. record the volume to correct # of decimal places. 5. carefully add metal from step 3 to the liquid in the graduated cylinder 6. tap the graduated cylinder to remove air bubbles 7. record the new volume on the graduated cylinder 8. use displaced volume (volume in step 7- volume in step 4=displaced volume) as the volume of the metal added...then calculate the density of the unknown metal. (density= mass/volume)
describe the procedures for separation of sand & sodium chloride
1. obtain filter paper, fold into 4ths, ID it with initials in pencil, and record its mass. 2. record mass of a 250 mL erlenmeyer flask and label white area so you know which one is yours in the oven versus your classmates 3. evap dish with only sand & sodium chloride--> add DI water until 1/2 full and stir the solid and liquid 4 mins or enough time for NaCl to dissolve. 4.1st pour the liquid through a gravity funnel(equipped with filter paper from step 1) 5. then transfer the sand to the gravity funnel & wash all sides of evap dish 6. collect the filtrate (salt water) in the 250 mL flask, Rinse the solid sand with DI water so all NaCl has been rinsed into flask. 7. remove filter paper with sand from the funnel and place on watchglass in oven for 15 min to dry. 8. allow to cool for 15 min, then record the mass of filter paper and dried sand. 9. while sand is drying in oven, obtain a hotplate and use it to heat salt water solution to get rid of all the water (evaporation). as water evaporates, salt crystals appear in flask! 10. as salt crystals appear, remove the flask from hotplate to prevent splattering/popping of saltwater solution 11. place flask in oven to evaporate last bit of condensation on flask. 12. once all water is evaporated, remove & allow to cool (elbow test) 13. get mass of flask and remaining NaCl 14. DON'T FORGET! wash all glassware with soap & brush, rinse well, and drain
Describe procedures for ammonium chloride sublimation lab
1. obtain sand, salt, ammonium chloride mix sample. put evaporating dish on balance & record mass. then add 2-3 g of sample on evap. dish & measure mass. 2. using fisher burner, ring stand, iron ring, and wire gauze set up in a hood, heat the evaporating dish with 2-3 g of sand, salt, ammonium chloride mix sample for about 5 mins. (white vapors escaping off the top is ammonium chloride escaping into the atmosphere) 3. after 5 mins, remove sample & let cool 10 min. cool enough once you can touch dish w/ insides of elbows & its not hot. (a warm sample's mass is inaccurate b/c of convection currents and will be artifically LOW in mass) 4. once cooled, obtain and record mass of evap dish and sample 5. repeat heating/cooling/mass process to ensure ammonium chloride is gone (the mass should be decreasing--NOT increasing!) 6. the process is complete when the sample's mass drops each trial by </= 0.002 grams
describe lab procedures for the: measuring density & temperature of ice water lab
1. using the 250 mL beaker from step 6 of the "wet lab", add a small shovel of crushed ice & swirl liquid 4 minutes with a thermometer. Record the temperature of the water in degrees celsius to the correct # of decimal places for this measuring device (1 decimal place past the smallest mark on the thermometer) 2. take a 10 mL graduated cylinder and place b/w 7-9 mL of water (no ice) from the beaker in step 1 above. measure the volume to correct # of decimal places) 3. obtain an erlenmeyer flask and record its mass to the precision of the balance. 4. pour the water measured in step 2 into the weighed erlenmeyer flask & record the new mass 5. calculate the mass of the ice-water 6. use the mass and volume to calculate the density of the water Density=mass/ volume
when do you use... 1. fire extinguisher 2. shower 3. eye wash fountain
1. when there's a fire 2. if chemical spill is large and on clothes 3. if chemical splatters on face/eyes & is burning
describe the procedures for the ideal gas law lab
1.obtain a sample of magnesium metal and record mass. do NOT exceed mass of 0.046 g. 2. fold & twist metal in copper wore cage (cage should support metal) 3. use rubber stopper of eudiometer to check if stopper and cage will fit 4. remove stopper and continue in the hood 5. wearing gloves, with a disposable pipet, place 20 mL of HCl in the eudiometer tube 6. add DI water to the eudiometer tube(you may see 2 different layers b/c of different densities) 7. add water until 100% full while AVOIDING mixing HCl and H2O 8. insert stopper with wire cage(no reaction yet) 9.place gloved finger over stopper's hole & invert the eudiometer, placing the finger attach stoppered end into a 600 mL/1 L beaker of water (the water should cover stopper, about 250 mL) 10. acid should slowly diffuse through inverted tube and as it reaches the metal, bubbles will appear. the bubbles are H2 and will rise and collect at the top. allow time for Mg to disappear and nothing remains except copper wire cage. If pieces of Mg remain/escape, repeat the experiment. if more than can be quanitified by the eudiometer of H2 is produced (i.e. Mg>0.046 g), or if gas escaped, repeat the experiment. 11. volume of solution in beaker < volume of solution in eudiometer tube which means pressure inside eudiometer tube is different than the pressure outside. since we're using barometric pressure/atmospheric pressure to calculate pressure inside the tube, we need the pressures to be equal which is done by ensuring liquid level inside=liquid level outside- hence equalization chamber 12. when reaction is complete, with finger remaining over the hole in the stopper, take the eudiometer to the tall container of provided water (aka equalization chamber) 13. submerge eudiometer tube in equalization chamber until 2 levels of liquid (outside & inside) are at the same point & then read the volume of gas collected in the eudiometer while its still in equalization chamber 14. discard liquid in eudiometer to appropriate waste container 15. make sure value of barometric pressure is in mmHg!! record air temp in lab 16. repeat experiment (assume barometric pressure is same in room in both trails) 17. find the average of the 2 measurements: (exp.1+exp. 2)/2=average
Describe the procedures of a dry lab:volume of a box:a study in uncertainty
1.obtain rustic meter stick with the 3 calibrated scales and cardboard box 2.using side A measure distance if each side of the box & record with proper # of sigfigs in meters 3.calculate the box's volume by L x W x H = V &record answer to correct sigfigs 4. repeat steps 1-3 using side B of meter stick which is calibrated to nearest 1/10th m/cm ...remember calibrated tools should be read with an estimate of 1 decimal place past the smallest calibration point. the units should be m ^3 for volume 5.repeat steps 1-3 using side C of meter stick which is calibrated to nearest 1/100th m/cm ...remember calibrated tools should be read with an estimate of 1 decimal place past the smallest calibration point. the units should be m^3 for volume 6. convert volume m^3 to Liters volume (m^3)= 1,000,000cm^3/1m^3 x 1 L/1000 cm ^3 = Volume (L)
describe the lab procedures for: a wet lab:measuring volume
1.obtain styrofoam cup 2.fill cup with deionized water until 75% full 3. pour a portion (<100mL) of water into a 100mL graduated cylinder 4. measure the volume poured to the precision of the graduated cylinder (+/- 0.1mL). transfer that water to a 250mL beaker 5.transfer the remainder in the cup to the graduated cylinder.measure that volume of the 2nd portion in the graduated cylinder 6. add your volumes to get a total volume of water that was in the cup. transfer the 2nd portion of DI water to the same 250mL beaker. 7. convert the volume from mL to L 1000mL= 1 L
what is the precision of the volume of a volumetric pipet that says "TD, 20 degrees Celsisus +/- 0.02 mL" when recording a 10mL volume?
10.00 mL (not 10.0 mL or 10 mL)
boiling point of water
100.0 degrees celsius or 373.15 kelvin
convert 143.1 mL to L
1000 mL= 1 L 143.2 mL X (0.001 L)/(1 mL)=0.1432 L
how do you convert from mL to L?
1000mL=1 L
Mass of 250 mL beaker is 97.436 g. Mass of 250 mL beaker and NaCl is 106.059 g. What is the mass of NaCl?
106.059g - 97.436 g = 8.623 g
what is the theoretical yield of copper metal in grams if the original mass of CuCl2 was 3.021 g?
3.021 g CuCl2 x (1 mole CuCl2)/ (134.45 g CuCl2) x (3 mole Cu)/ (3mole CuCl2) x (63.54 g Cu) / (1 mole Cu) =1.427700558 g Cu =4 sigfigs, 1.428 g Cu
A bottle of Tums is $3.99 with 72 1000mg tabets. What is the cents per tablet?
399cents/72 tablets=5.5 cents/tablets
The mass of a metal is 22.971 g. The displaced volume of the metal is 1.6 mL. What is the density?
D= M/V =22.971 g/ 1.6 mL =14.36875 g/mL 2 sigfigs so... =14 g/mL
Mass of salty ice water is 8.507 g. Volume of salty ice water is 8.56 mL. What is the density?
D= M/V =8.507 g / 8.56 mL =0.993808... g/mL =3 sigfigs so... =0.994 g/mL
Mass of ice water is 7.590 g. The volume is 7.910 mL. What is the density?
D=M/V =7.590g / 7.910 mL =0.9595448...g/mL =0.960 g/mL
Pbar = 761.8 mmHg. PH2O=18.9 mmHg. what is the pressure of H2 from Dalton's Law in mmHg?
Dalton's Law of Partial pressuresL PH2=Pbar-PH2O 761.8-18.9=742.9 mmHg
Is there a difference in the density & temperature obtained for the ice water versus the salty ice water? WHY?
Density for: salty ice water=0.994 g/mL ice water= 0.960 g/mL Temperature for: salty ice water=6.2 degrees Celsius ice water= 17.5 degrees Celsius The density for salty ice water was greater than of ice water. The temperature of salty ice water was lower than that of ice water because the salt depresses the freezing point. Also, salt adds more density.
In the Separation of a Mixture: Sand, Salt, Ammonium Chloride lab, were the sand, salt, and ammonium chloride separated using physical or chemical changes?
PHYSICAL!
What is the ideal gas law?
PV=nRT
Pbar= ? + ?
Pbar= PH2+PH2O
3 CuCl2 (aq) + 2 Al(s) ---> 3 Cu(s) + 2 AlCl3 (aq) is a redox _____ because it is gaining electrons and its oxidation state is decreasing
REDUCTION
why does the solution turn blue during the copper lab?
Solution should be BLUE/BLUE-GREEN, characteristic of Cu ^2+ ions in water.
Describe the 3 physical appearances of the 3 components, sand (silicon dioxide SIO2), sodium chloride (NaCl), and ammonium chloride (NH4Cl) after each was separated from the mixture.
The ammonium chloride was sublimated into the atmosphere and looked like white vapors. The resulting sand and sodium chloride appeared yellowish and tan. The dried sand on the filter paper appeared as beach sand- dry beige crystals. The salt appeared as tiny, shiny, white crystals.
You measured 3 sides of a box with a meter stick and found it to be 0.322 m Long, 0.220 m wide, 0.140 m high. What is the volume of box to correct sigfigs & units?
V= L x W x H =0.322m X 0.220m x 0.140m =0.0099176 m^3--> 3 sigfigs, so... =0.00992 m^3
You measured 3 sides of a box with a meter stick and found it to be 0.32 m Long, 0.22 m wide, 0.13 m high. What is the volume of box to correct sigfigs & units?
V= L x W x H =0.32m X 0.22m x 0.13m =0.009152 m^3--> 2 sigfigs, so... =0.0092 m^3
You measured 3 sides of a box with a meter stick and found it to be 0.3305 m Long, 0.2305 m wide, 0.1405 m high. What is the volume of box to correct sigfigs & units?
V= L x W x H =0.3305m X 0.2305m x 0.1405m =0.0107033251 m^3--> 4 sigfigs, so... =0.01070 m^3
You measured 3 sides of a box with a meter stick and found it to be 0.3 m Long, 0.2 m wide, 0.1 m high. What is the volume of box to correct sigfigs & units?
V= L x W x H =0.3m X 0.2m x 0.1m =0.0006 m^3
Discuss why you got something beside 100 % of total original components in the Separation of a Mixture: Sand, Salt, Ammonium Chloride lab. Where could you improve your tecnhique in the future?
We were unable to fully sublimate the ammonium chloride from the mix as we discovered when we boiled the saltwater on the hotplate and realized the vapors coming out were more dense than steam. Additionally, as soon as salt crystals appeared when boiling, we should have removed the flask rather than allowing it to continue heating because the salt crystals may have trapped water inside
describe the effects of each solution on the textures, masses, and volumes of the potato disks. in each case, what happened to the cells in the potato disks. in each case what happened to the cell in the potatoes and which direction did the water flow? a)20% w/v NaCl b)0.9% w/v NaCl c)DI water
a)20% w/v NaCl: the texture went from porous and firm to gooey,slimy, and flexible. mass decreased. water flowed out from the cells into the solution-hypertonic b)0.9% w/v NaCl: texture went from porous and firm to more flexible but still sturdy. mass descreased. volume stayed the same. very little occurred-isotonic c)DI water: the texture went from porous and firm to even more firm and swollen. mass increased alot. volume increased. water went into cells (hypotonic)-cells swollen
What is happening to the copper II ions in the copper lab? What about the metallic aluminum?
copper II ions (Cu+2) become metallic copper (Cu^0). the metallic aluminum (Al^0) becomes dissolved aluminum ion (Al +3)
how do you convert from degrees celsius to kelvin and from kelvin to degrees celsius?
degrees Celsius=K-273 K= degrees celsius + 273
How do you calculate density?
density= mass/volume
if too much substance is taken out of its container, what do you do with the excess?
do NOT return it to original container b/c contaminants stock bottle for later students. excess should be discarded in appropriate waste location
redox reactions involve ___ exchanges
electron
what is used to collect the H2 during the ideal gas law lab?
eudiometer
to separate the NaCl from the water and salt mix what physical means did you use? what did it look like?
evaporation; salt crystals appeared on flask walls
what experimental errors could occur in the copper lab that would cause you to get something besides 100% recovery?
excess moisture, not enough acetate to dry out copper metal, not enough drying time in the oven, not having enough time to cool down, incomplete reaction (persistent green color)
to separate the sand, silicon dioxide, SIO2 from the sand and salt mix, what physical means did you use?
filtration
The copper II ions ___ electrons and are thus reduced. Cu ^2+ (aq) + 2e- --> Cu ^0 (s)
gain
if your reduced, you have ___ e-
gained
How would you convert mass of CuCl2 to moles of CuCl2 using the molar mass of 1 mole of CuCl2?
grams CuCl2 X (1 mole of CuCl2)/ (grams CuCl2)
you know you had an incomplete reaction in the copper lab if there is a persistent ___ color
green
Kelly puts a hot substance on a weighboat and then puts it on the balance for the mass to be read .how would you expect the heat of the substance to effect the mass reading?
heat causes ARTIFICIALLY LOW MASSES!!
hypertonic have ___solute concentrations, so they are shriveled
high
Percent calculations: what is the % mass of NaCl relative to the total mass of the sample if the total mass of the sample is 2.894 g and the mass of the NaCl was 1.545 g?
mass %= mass of pure component/ total mass of sample X 100% = 1.545 / 2.894 X 100% =53.38631652 % 4 sigfigs so... =53.39%
Percent calculations: what is the % mass of ammonium chloride relative to the total mass of the sample if the total mass of the sample is 2.894 g and the mass of the ammonium chloride was 0.079 g?
mass %= mass of pure component/ total mass of sample X 100% =0.079/2.894 X 100% =2.72978564% 2 sigfigs so.... = 2.7%
Percent calculations: what is the % mass of sand (silicon dioxide) relative to the total mass of the sample if the total mass of the sample is 2.894 g and the mass of the sand was 1.695 g?
mass %= mass of pure component/ total mass of sample X 100% =1.695/2.894 X 100% =58.569... % 4 sigfigs so... =58.57 %
How do you calculate mass %?
mass %= mass of pure component/total mass of sample X 100%
If the mass of copper II chloride is 3.021 g CuCl2 and the molar mass of CuCl2 is 134.45 g/mol CuCl2, then how many moles of CuCl2 were dissolved in solution?
mass of CuCl2/ MM of CuCl2= moles CuCl2 3.021 g/ 134.45 g/mol =0.0224693194 mol CuCl2 4 sigfigs= 0.02247 moles CuCl2
how do you calculate mass when you have density and volume given?
mass=density X volume
If you have 5.00 g of CuCl2, how many moles of CuCl2 are present?
moles CuCl2= 5.00 g CuCl2/ 134.5 g/moles CuCl2 <-- MM of CuCl2 =0.03719 moles CuCl2... 3 sigfigs, so 0.0372 moles CuCl2
the molarity of HCl used is 0.6895 M and the volume of HCl used is 25.00 mL. so how many moles of HCl is added?
moles=M x L 0.6895 x 25.00 = 0.0172375 M HCl needs to be 4 sigfigs, so 0.01724 moles HCl added
For every mole of CuCl2 you start with, there should be the ____ number of moles of the copper cation... CuCl2 (aq) --> Cu ^2+ (aq) + 2 Cl- (aq) For each mole of CuCl2 there is on mole of Cu ^ 2+, 1:1 ratio due to conservation of mass law
same!
number of moles of NaOH in the acid base titration lab will be ____the number of moles of HCl
same. 1:1 ratio!!
sand's chemical name & formula are:
silicon dioxide SIO2
SAFETY: where is the fire extinguisher?
one by each door under red signs
where is the eyewash fountain?
one by shower, one by sink
the copper lab was an ____ - ____ reduction reaction using aluminum wire and copper II chloride solution
oxidation-redox
to increase an oxidation state, the species has to lose electrons (aka be ____) while the other species has to gain electrons (be ___) and its oxidation state decreases
oxidized; reduced
calculate the percent error for average R if it is 0.083 L-atm/mol-K
percent error = |(accepted-experimental)/ accepted| x 100% = |(0.0821-0.083)/0.0821| x 100% =1.096224117% =2 sigfigs, so 1.1%
what evaluates effectiveness in the copper lab: hint... it is the ratio of what you recovered compared to what was predicted...?
percent yield % yield= |experimental yield/theoretical yield| X 100 %
what acts as the semipermeable membrane in the osmosis lab?
potato cell walls
____added may depress the freezing point & elevate the boiling point... f.e. when rock salt is added to icy roads to prevent icing over.
salt
ammonium chloride (NH4Cl) is a type of ___
salt
what effect does salt have on temperature?
salts added may depress the freezing point & elevate the boiling point... f.e. when rock salt is added to icy roads to prevent icing over.
The moles of metallic copper ions should be the _____ as the moles of the original copper II ions due to the law of the conservation of mass.
same
isotonic have ___ concentration and do not change
same
what was the purpose of the ideal gas law lab?
to determine the gas constant R of hydrogen gas
why do we use titrations?
to determine the unknown concentration of an acid
What was the purpose of the : Separation of a Mixture: Sand, Salt, Ammonium Chloride lab?
to separate 3 compounds in a mix by using their PHYSICAL property differences. silicon dioxide (SIO2) or sand, sodium chloride (NaCl) or salt, and ammonium chloride (NH4Cl) another salt, was separated into pure substances using SUBLIMATION (where a pure compound turns into a gas from a solid) and evaporation (where the change is from a liquid to a gas)
what is osmosis?
transition of solvent molecules from an area of low solute concentration to an area of high solute concentration through a semi permeable membrane
how do you find the molar mass of CuCl2?
use periodic table atomic masses to calculate. 1(Cu) + 2(Cl)= MM in g/mol of CuCl2 63.5 + 2(35.5) =134.5 g/mole of CuCl2
how do you convert volume m^3 into Liters?
volume (m^3)= (1,000,000cm^3)/(1m^3) x (1 L)/(1000 cm ^3) = Volume (L)
how do you calculate the volume of a rectangle and what is the units?
volume of rectangle= LxWxH and units are m^3 or cm^3
The volume of water in a graduated cylinder is 49.5 mL. An unknown metal added to this increases the volume to 51.1 mL. What is the displaced volume?
volume of sample= final water level- initial water level 51.1 mL - 49.5 mL= 1.6 mL
how do you calculate volume when mass and density are given?
volume= mass/density
what is sublimation?
when a pure compound goes from a solid directly to a gas, physical change