1A End of Lab Questions Notes

Transcription

1 1A End of Lab Questions Notes 11/1/18 Lab 9, Part 1 Lava lamp 1 Ethanol is not soluble in vegetable oil because Ethanol is polar and vegetable oil is non-polar 2 Most lava lamps use water and oil A secret substance is added to the oil to its density When cold (or room temperature), the density of the is higher than the density of Fill in Blanks 1, 2, and 3 a Blank 1 = increase b Blank 2 = oil c Blank 3 = water 3 You mixed two soluble liquids together, eg, ethanol and water, to get a liquid mixture with a different density a Which two liquids did you mix together to get a liquid mixture with a different density? b Liquid 1 and % Liquid 1 in the mixture c Liquid 2 and % Liquid 2 in the mixture d density in g/ml of your Liquid 1-Liquid 2 mixture Give a number only; do not include text e My lava lamp 10/30/18 Lab,8 Part 2B 1 Report the food item you used in lab today 2 Report the color of the food item 3 Report the wavelength(s) of the peak(s) in the absorption spectrum of your food item 4 Report the wavelength of the peak in the absorption spectrum of the food coloring that matches your food item 5 Is the color from your food from food coloring? Give reasons based on Questions 3 and 4 If the absorption spectrum of the color you extracted from your food is the same (same peak wavelength(s)) as the absorption spectrum of the food color, then the color from your food is from food coloring If the absorption spectrum of the color you extracted from your food is different (different peak wavelength(s)) as the absorption spectrum of the food color, then the color from your food not is from food coloring 6 The absorption spectrum of red food coloring shows a peak at 525 nm You extract the red color from red candy The absorption spectrum of this red color shows a peak at 550 nm Draw a conclusion from these data The wavelength of the peak of the red food coloring (525 nm) is different from the wavelength of the peak from the red candy Conclusion: the red color from the red candy is not from red food coloring NOTE: a 25 nm difference in wavelength is a significant difference You would be see a different color nm is green, 550 nm is yellow 7 See your Table 4 data and results

2 a What is the most important piece of data you collected in today's experiment? Part 2B Two different food colors Amount of food color used Amount of water used Absorption spectrum of each food color and mixture of the two food colors Wavelength of each peak in nm Problem 2 Food item, eg, strawberries Solvent used to extract color, eg, water Absorption spectrum of color extracted from food Wavelength of each peak in nm b What result did you determine from the data you collected from the previous question? Part 2B ΔE from wavelength (ΔE = hc/ƛ ) New color from mixture of two food colors is either due to a chemical reaction or just mixing Problem 2 Color from food item is the same or different than the color from food color 10/25/18 Lab 8, Part 2A Absorption spectra 1 Sunglasses what is the background in the background spectrum before you measured the spectrum of your sunglasses? The background spectrum is air 2 If sunglasses provide 100% UV protection, what wavelength range should be absorbed by the sunglasses? Give numbers UV wavelengths between nm should be absorbed by the sunglasses 3 What is the % transmittance of UV light for sunglasses with 100% UV protection? If UV wavelengths between nm are absorbed, the % transmittance should be 0% If UV wavelengths between nm are NOT absorbed, the % transmittance should be 100% 4 Of all the sunglasses tested in lab today, which sunglasses provided the best UV protection? Give reasons for your choice a Sunglasses brand b cost in $ c Absorbance reading between nm d % transmittance reading between nm e Would you buy these sunglasses?

3 10/23/18 Lab 8 H emission and Lab 6 Rust results Hydrogen emission spectrum 1 a Which transition produced the blue (480 nm) emission line? Give a two digit number with the initial n first and final n second Do not use a comma between the numbers Example: 23 means ni = 2 and nf = 3 n i = 4 and n f = 2 b What is the energy in kj/mole of this emission line? Give a number only; do not include text ΔE = hc/ƛ = (663x10-34 J sec)(300x10 8 m/sec)/(480x10-9 m) = 414x10-19 J Use Avogadro s number to convert from J/photon to kj/mole: (414x10-19 J/photon)(602x10 23 photon/mole)(1 kj/1000 J) = 249 kj/mole c H produces an emission line at 1010 nm In what region of the electromagnetic spectrum is this wavelength? IR d What electron energy states in H produce the 1010 nm line? Give a two digit number with the initial n first and final n second Do not use a comma between the numbers Example: 23 means ni = 2 and nf = 3 n i = 7 and n f = 3 How to prevent an iron nail from rusting Measure the mass of the rusted nail Mass of rusted nail - original mass of nail = mass of that reacts Calculate mass of Fe that reacts from mass of that reacts % nail that rusted = mass of Fe that reacts/original mass of nail x a Report the % nail that rusted using a protective coating State the protective coating you used Protective coating = paint, white out, nail polish b Report the % nail that rusted using a sacrificial anode State the sacrificial anode you used sacrificial anode = Mg or Zn c Report the % nail that rusted by plating the nail with a less easily oxidized metal State the less easily oxidized metal you used Coat the nail with copper by placing nail in Cu(NO 3 solution You saw the nail turn black, then brown or red d Which method worked best in preventing the iron nail from rusting? The method with the lowest % nail e Give reasons for your answer to part d Include numbers The method that has the lowest % nail that rusted is the method that worked best to prevent the nail from rusting Nail control experiments 3 a Report the % nail that rusted in air b Report the % nail that rusted in water

4 c Report the % nail that rusted in HCl d Report the % nail that rusted in bleach e Which experiment produced the most rusted nail? The method that has the highest % nail f Give reasons for your answer to part e Include numbers The method that has the highest % nail that rusted is the method that produced the most rusted nail 10/18/18 Lab 8, Part 1 Emission spectra 1 Describe how red light is produced in a Ne lamp Electrical energy is absorbed by Ne so an electron undergoes a transition from a lower energy state to higher energy (excited) state An electron in the higher energy state undergoes a transition to a lower energy state and releases energy in the form of red light 2 How many visible lines did you observe in the Ne emission spectrum? More than 5 3 Based on your answer to Question 2, how many energy states in Ne based on emission spectra? 1 line from 2 energy states 2 lines from 3 energy states 3 lines from 3 or more energy states 4 lines from 4 or more energy states 5 lines from at least 4 energy states depending on ΔH between electron energy states 4 a Identify Unknown A b Identify Unknown B c What element is in the fluorescent lights in the room? 5 a What color did the pickle glow? yellow b What salt is in the pickle? NaCl 10/16/18 Lab 7, Part 4 1 Hot pack data and results a List the salts that could be used to make a hot pack CaCl 2, LiCl, MgSO 4, and CaSO 4 can be used to make a hot pack These salts have a ΔH of reaction < 0 b Which salt is the cheapest (least expensive) to make per pack? Include cost c Which salt is the next cheapest to make per pack? Include cost d Which salt is the safest (least hazardous) to use? e Which salt is the next safest to use? f Report the two salts you used to experimentally test for performance Choose two salts based on lowest cost and safety (least hazardous)

5 g Which salt performed better? Include numbers to support your answer The ideal performance for a hot pack is the temperature should increase to 40 o C and maintain that temperature for 10 minutes h Based on cost, safety, and performance, which salt would you use for a hot pack? Give reasons for your choice The ideal salt should be cheap, safe, and work for 10 minutes at 40 o C 2 Cold pack data and results a List the salts that could be used to make a cold pack NaCl, NH 4 Cl, NaNO 3, NH 4 NO 3, KNO 3 (don t have) These salts have a ΔH of reaction > 0 b Which salt is the cheapest (least expensive) to make per pack? Include cost c Which salt is the next cheapest to make per pack? Include cost d Which salt is the safest (least hazardous) to use? e Which salt is the next safest to use? f Report the two salts you used to experimentally test for performance Choose two salts based on lowest cost and safety (least hazardous) g Which salt performed better? Include numbers to support your answer The ideal performance for a cold pack is the temperature should drop to 0 o C and maintain that temperature for 10 minutes h Based on cost, safety, and performance, which salt would you use for a hot pack? Give reasons for your choice The ideal salt should be cheap, safe, and work for 10 minutes at 0 o C 10/11/18 Lab 7, Part 3 Flex fuel 1 a Report the alcohol you used in your Run 1 Ethanol or isopropanol (rubbing alcohol) b Report the mass in g of alcohol Give a number only; do not include units 5 drops of alcohol is approximately 004 g c Report the volume in liters of your bottle Give a number only; do not include units Fill your bottle completely with water and pour the water into a graduated cylinder to determine the volume of the bottle d Calculate the experimental mole ratio of alcohol to Give a number only; do not include units Moles of alcohol = mass/molar mass Calculate Moles of air from PV=nRT (P = room pressure = 1 atm, V = bottle volume, R = 0082 l atm/mole K, T = room temperature in K) Air is 20% so moles of = moles of air x 020 Mole ratio of alcohol to = moles of alcohol/moles of 2a You burn ethanol in a bottle When you let the bottle cool, you see some liquid in the bottle What is the liquid? Give a one word answer water

6 b 05 ml of ethanol is burned Calculate the theoretical yield of water in g Give number only with no units balanced chemical equation: C 2 OH (l) + 3 (g) 2 C (g) + 3 H 2 O (g) The mole ratio of C 2 OH (l) to H 2 O (g) is 1:3 05 ml C 2 OH x (079 g C 2 OH/ml C 2 OH) (1 mole C 2 OH/46 g C 2 OH)(3 moles H 2 O /1 mole C 2 OH)(18 g /mole H 2 O ) = 046 g H 2 O = theoretical yield of water c The % yield of water is 75% Where did some of the water go? Escaped from bottle when you combusted the alcohol 10/9/18 Lab 7, Part 2 1 Natural gas is methane (CH 4 ) What is the optimum mole ratio of methane to oxygen to produce a hot flame in a Bunsen burner? moles of methane = / mole of oxygen From the balanced chemical equation: CH 4 (g) + 2 (g) C (g) + 2 H 2 O (g) The mole ratio of CH 4 (g) to 2 (g) is 1:2 So moles of methane = 05/mole of oxygen 2 What color should the flame be when methane burns in the mole ratio in Question 1? Flame should be blue = this should be the hottest flame temperature 3 a CH 4 burns in air to produce C (g) and H 2 O (l) Calculate the heat of reaction in kj/mole Report number only with no units Balanced chemical equation: CH 4 (g) + 2 (g) C (g) + 2 H 2 O (l) Look up ΔH f of each reactant and product Note ΔH f of H 2 O (l) is different that H 2 O (g) Then, apply Hess law to calculate ΔH of reaction ΔH of reaction = -890 kj/mole 3 b If you burn 01 g of CH 4, how much heat is released in kj? Report number only with no units ΔH of CH 4 (g) combustion reaction = (-890 kj/mole)(1 mole CH 4 /16 g CH 4 )(01 g CH 4 ) = -556 kj (for H 2 O (l) product) (-802 kj/mole)(1 mole CH 4 /16 g CH 4 )(01 g CH 4 ) = -501 kj (for H 2 O (g) product) 10/4/18 Lab 7, Part 1 1 a Unknown Metal Letter b Your experimental specific heat of this metal in J/g o C c True specific heat of this metal in J/g o C Specific heat of Au = 013 J/g o C Specific heat of Ag = 024 J/g o C Specific heat of Al = 090 J/g o C Specific heat of Cu = 039 J/g o C Specific heat of brass = 035 J/g o C Specific heat of Zn = 039 J/g o C Specific heat of Fe (stainless steel) = 045 J/g o C

7 Specific heat of Mg = 102 J/g o C d % error in specific heat % error = (experimental specific heat - true specific heat)/(true specific heat) x 100 e Which is the identity of this metal? 2 a Unknown Metal Letter b Your experimental specific heat of this metal in J/g o C c True specific heat of this metal in J/g o C d % error in specific heat e Which is the identity of this metal? g of Fe at 100 o C is added to 50 ml of water at 25 o C Calculate the final temperature in o C - Heat lost by hot Fe = heat gained by cold water - (mass of Fe)(specific heat of Fe)(T f - T ife ) = (mass of H 2 O)(specific heat of H 2 O)(T f - T ih2o ) - (531 g) (045 J/g o C) )(T f o C) = 50 g)(418 J/g o C) )(T f - 25 o C) Solve for T f = 327 o C 10/2/18 Lab 6, Part ml of hexane is added to Br 2 (aq) 1 ml of _ NaI water is added and shaken The resulting mixture separates into 2 layers The top layer is purple 2 The observations from Question 1 tell you Br 2 is a stronger oxidizing agent than _ I 2 Fill in the blanks Write a net ionic equation that represents this reaction Br NaI I NaBr Br Na I - I Na Br - Net ionic equation: Br I - I Br - 3 Rank the halogens (Cl 2, I 2, and Br 2 ) in order of oxidizing strength Cl 2 > Br 2 > I 2 4 You can buy chlorine bleach at the store Why do you think fluorine (F 2 ) is not used in bleach you can buy at the store? Cl 2 is the strongest oxidizing agent that we test in this experiment F 2 is a stronger oxidizing agent than Cl 2 and is too strong of an oxidizing agent for general cleaning use 9/27/18 Lab 6, Part 1 How to prevent an iron nail from rusting 1 Why won t letting an oxide coating form on an iron nail prevent it from rusting? Rust (Fe 2 O 3 ) forms throughout the entire piece of iron, not just on the surface

8 2 a Why is Zn considered a sacrificial anode and not Cu? Zn is more active than Fe and is preferentially oxidized over Fe Cu is less active than Fe and is not preferentially oxidized b What other metal, besides Zn, that could be used as a sacrificial anode? See the Activity Series Any metal that is more active than Fe can be used as a sacrificial anode, eg, Zn, Pb, Al, Mg 3 Which method do you think will work best to prevent an iron nail from rusting? Choose a method You will find out in a month if you chose the right method 4 56 g of Fe rusts How many g of rust forms? 4 Fe Fe 2 O 3 56 g Fe (1 mole Fe/56 g Fe) (2 moles Fe 2 O 3 /4 moles Fe) ( 160 g Fe 2 O 3 /mole Fe 2 O 3 ) = 80 g Fe 2 O 3 9/25/18 Lab 5, Part 3 Acid content in soda 1 Soda brand you used 2 Why do you need to let your soda go flat before doing your titration? The C gas bubbles changes (increases) the volume of soda C reacts with water to form carbonic acid (H 2 ) We want to know the citric acid content, not the citric acid and carbonic acid content in soda 3 a What volume in ml of soda did you use in your titration? Give a number only; do not include text b What was the concentration in M of KOH you used to neutralize the acid in soda? Give a number only; do not include text c What was the volume in ml of KOH you used to neutralize the acid in soda? Give a number only; do not include text d What is the mole ratio of acid to KOH in this neutralization reaction? Balanced chemical equation: 1 C 6 O KOH 3 H 2 O + KC 6 O 7 So 1 C 6 O 7 : 3 KOH or 033 e What was the concentration in M of citric acid in soda? Give a number only; do not include text Concentration of citric acid in Molarity = ( moles KOH/liter) x (volume of KOH in liters) x (1 mole C 6 O 7 /3 moles KOH) x (1/volume of soda in liters) 4 Summarize your results in one sentence Include numbers Example: We determined the average concentration of citric acid in (soda brand name) is M based on two titrations of the soda with M KOH solution 9/20/18 Lab 5, Part 2 1 a Report the experimental concentration in Molarity of your KOH solution Report the average concentration of your two titrations b Report the experimental concentration in Molarity of acetic acid in your vinegar Report the average concentration of your two titrations

9 c Convert the Molarity from 1b to % acetic acid by volume Molarity units are moles/liter of solution Example: 095 M acetic acid (095 moles acetic acid/liter)(1 liter/1000 ml)(60 g acetic acid/mole acetic acid)(1 ml acetic acid/1049 g acetic acid) x 100 = 54% acetic acid d Calculate the % error in vinegar concentration Use 5% or 087 M as the true concentration % error = (true concentration - experimental concentration)/true concentration x 100 Example: % error = ( )/087 x 100 = 92% error 2 Acid content in vinegar 965 ml of 105 M NaOH is required to neutralize 1000 ml of vinegar a Calculate the moles of NaOH Balanced chemical equation: NaOH + HC 2 NaC 2 + H 2 O Moles of NaOH = Molarity x volume in liters = 105 M x l = moles NaOH b Calculate the moles of vinegar that reacts with NaOH Moles of vinegar = moles of NaOH = moles c Calculate the Molar concentration of acetic acid in vinegar Molarity of acetic acid = moles of acetic acid/volume = moles/ l = 101 M 9/18/18 Lab 5, Part 1 1 Name the two substances in baking powder that are acids or the source of acid Ca(H 2 PO 4 (3 moles of this compound produces 7 moles H + ) NaAl(SO 4 (1 mole of this compound produces 3 moles H + ) 2 a Based on your data, what is the mass ratio of baking powder to flour to make the fluffiest pancakes? State the mass of baking powder, mass of flour, and height of pancake to support your answer b As you make pancakes, you see big bubbles form and pop When you see this happen, will your pancake be fluffier or flatter? When the C gas bubbles pop, your pancake will be flatter The bubbles are not trapped in the pancake to make it rise to a fluffy pancake c As you make pancakes, you see big bubbles form and pop Does this observation tell you baking soda is the limiting reactant or excess reactant? Give reasons Compare the amounts of baking soda to flour to make pancakes If bubbles form and pop (and escape), there is too much baking soda (and not enough flour to trap the bubbles) so the baking soda is the excess reactant teaspoon of baking powder has a mass of 12 g Calculate the mass in g of H + produced from the sodium aluminum sulfate (Remember baking soda has 21% sodium aluminum sulfate) NaAl(SO H 2 O Al(OH) 3 + Na SO H teaspoons of baking powder = 12 g 12 g x 21% NaAl(SO 4 = 0252 g NaAl(SO 4 ) g NaAl(SO 4 x (1 mole NaAl(SO 4 /242 g NaAl(SO 4 ) x (3 moles H + /1 mole H + ) x (1 g H + /mole H + ) = g H +

10 9/11/18 Lab 4 1 You add 100 g of Na 2 to water You add 1 drop of phenolphthalein and the solution turns pink This observation tells you Na 2 is a base 2 You add vinegar (09 M acetic acid) to the Na 2 CO 3 solution from Question 1 Calculate the volume in ml of vinegar that reacts with Na 2 Balanced chemical equation: Na HC 2 NaC 2 + H 2 O + C (g) 100 g Na 2 /(1 mole Na 2 /106 g Na 2 )(2 moles HC 2 /1 mole Na 2 ) = 0018 moles HC 2 O 2 Molarity of HC 2 = moles of HC 2 /Volume so Volume = moles of HC 2 /Molarity = 0018 moles HC 2 / 09 moles/lter = 0020 liters 0020 liters (1000 ml/1 liter) = 20 ml of 09 M acetic acid 3 You want the solution to stay pink Should you use more or less of the volume of vinegar you calculated in Question 2? Na HC 2 NaC 2 + H 2 O + C (g) Solution is pink because it is a base so you want Na 2 (base) to be the excess reactant and vinegar to be the limiting reactant So use less vinegar (less than 20 ml) to keep the solution pink 4 Which reactant is the limiting reactant in Question 3? 5 a For your Lab 4 demonstration, white solid A is Choose a base that soluble in water, eg, KOH, NaH, Na 2 Mg(OH) 2 and Ca are bases but both are insoluble in water NaCl, Mg(NO 3, and Ca(NO 3 are neutral b For your Lab 4 demonstration, colorless liquid B is Liquid B is an acid that reacts with a base that produces C gas Liquid B is either HCl and HC 2-2- The base that reacts with this acid that produces C gas must contain H ion or ion, eg, NaH, Na 2 c For your Lab 4 demonstration, colorless liquid C is Liquid C reacts with the pink solution after Liquid B reacts with Solution A to form a white solid - 2- The pink solution is a base and contains excess base, either H ion or ion - 2- For Liquid C, identify a cation that combines with H ion or ion to form an insoluble solid - see Lab 4 Materials List and the solubility table - H compounds are soluble in water So, NaH cannot be used for Solid A 2- compounds are insoluble in water (with several exceptions) So, KOH and NaCl and NaH will not work because K + and Na + 2- will not combine with to form a precipitate (solid) Ethanol (C 2 OH) will not work because it is a molecular compound and does not have ions that can combine with CO 2-3 Vinegar (HC 2 ) will not work because it is a weak acid and only has a few ions in solution (H and C 2 ions will not combine with to form a precipitate (solid))

11 HCl will not work Although it is a strong acid, the H + and Cl - 2- ions will not combine with to form a precipitate (solid)) Ca has the Ca ion that could combine with to form a precipitate (solid) but Ca is not soluble in water and cannot be used as Liquid C Ca(NO 3 has the Ca ion that could combine with to form a Ca precipitate (solid) Ca(NO 3 is soluble in water and can be used as Liquid C Mg(NO 3 has the Mg ion that could combine with to form a Mg precipitate (solid) Mg(NO 3 is soluble in water and can be used as Liquid C 9/6/18 Lab 3, Part 2 1 a Which antacid did you make? b Actual yield in g of your antacid Give a number only; do not include text The actual yield of your antacid is the mass of dry antacid that you made in this experiment c % yield of your antacid Give a number only; do not include text % yield = (actual yield in g/theoretical yield in g) x 100 d If the % yield of antacid is not 100%, identify a specific step in your experiment that led to this error If the % yield is less than 100%, antacid is usually lost during the filtration step or not all of the reactants reacted If the % yield is greater than 100%, the antacid is probably not dry (still wet, not all of the water was removed) 2 NaOH (aq) reacts with AlCl 3 (aq) to form a solid: NaOH + AlCl 3 ---> a Write a balanced chemical equation for this reaction 3 NaOH + AlCl 3 ---> 3 NaCl + Al(OH) 3 b What is the chemical formula of the solid that is formed in this reaction? Solid is Al(OH) 3 See solubility table Al(OH) 3 is insoluble in water NaCl is soluble in water c Write a net ionic equation for this reaction 3 NaOH + AlCl 3 ---> 3 NaCl + Al(OH) 3 (s) See solubility table The soluble compounds dissociate into ions See table of common ions to check formula and charge Ionic equation: 3 Na OH - + Al Cl - ---> 3 Na + + Cl - + Al(OH) 3 (s) Net ionic equation: 3 OH - + Al > Al(OH) 3 (s) Spectator ions are Na + and Cl - 3 a 540 g of NaOH reacts enough AlCl 3 so all of the NaOH reacts Calculate the theoretical yield of Al(OH) 3 Convert mass of NaOH to moles of NaOH Use molar mass of NaOH for your conversion factor Convert moles of NaOH to moles of Al(OH) 3 Use coefficients in balanced chemical equation for your conversion factor

12 Convert moles of Al(OH) 3 to mass of Al(OH) 3 Use molar mass of Al(OH) 3 for your conversion factor 540 g NaOH (1 mole NaOH/40 g NaOH)(1 mole Al(OH) 3 /3 mole NaOH)(78 g Al(OH) 3 /mole Al(OH) 3 ) = 351 g Al(OH) 3 b You react 540 g of NaOH with 1000 g of AlCl 3 You collect 325 g of solid Al(OH) 3 Calculate the % yield of Al(OH) 3 % yield = (actual yield Al(OH) 3 in g/theoretical yield Al(OH) 3 in g) x 100 % yield = (325 g/351 g) x 100 = 926% 4 Baking soda (NaH ) is used as an antacid Explain why you cannot synthesize baking soda using a double replacement reaction like you did with Ca and Mg(OH Baking soda is soluble in water so you won t be able to do a double replacement precipitation reaction Double replacement precipitation reaction: AB + CD AD + CB + NaH + A = Na + -, D = H See solubility table: all Na + compounds are soluble in water - All H (bicarbonate) compounds are soluble in water So when the soluble Na + - compound (AB) reacts with the soluble H (bicarbonate) compound (CD), each product will be soluble in water (NaH (AD) and CB 9/4/18 Lab 3, Part 1 Na 2 + Ca(NO 3 ---> NaNO 3 + CaCO 3 1 Write a balanced chemical equation for this reaction Na 2 + Ca(NO 3 ---> 2 NaNO 3 + CaCO 3 e Write a net ionic equation for this reaction Use solubility table to determine solubility of each compound The soluble compounds dissociate (break up) into ions The insoluble compounds do not dissociate into ions Na 2 = soluble so it dissociates into 2 Na + and 2- Ca(NO 3 = soluble so it dissociates into Ca 2+ and NO 3 - NaNO 3 = soluble so it dissociates into Na + and NO 3 - Ca = insoluble so keep it as a compound Ionic equation: 2 Na Ca NO 3 ---> 2 Na NO 3 + Ca (s) Note Na + - and NO 3 are on each side of the equation so they cancel out These are spectator ions that do not participate in the reaction 2- Net ionic equation: + Ca > Ca (s) 2 Calculate the masses of Na 2 and Ca(NO 3 to make 1 g of Ca a molar mass of Ca in g/mole

13 molar mass of Ca = 40 g/mole molar mass of C = 12 g/mole molar mass of O = 16 g/mole So the molar mass of Ca = (16) = 100 g/mole b moles of Na 2 CO 3 Given mass of Ca = 10 g, calculate moles of CaCO 3 10 g Ca / 100 g/mole = 001 moles CaCO moles Ca x (1 mole of Na 2 /1 mole of Ca ) = 001 moles Na 2 CO 3 c mass of Na 2 in g 001 moles Na 2 x (106 g Na 2 /1 mole Na 2 ) = 106 g Na 2 CO 3 d moles of Ca(NO 3 ) 2 Given mass of Ca = 10 g, calculate moles of CaCO 3 10 g Ca / 100 g/mole = 001 moles CaCO moles Ca x (1 mole of Ca(NO 3 /1 mole of Ca ) = 001 moles Ca(NO 3 ) 2 e mass of Ca(NO 3 in g 001 moles Ca(NO 3 x (164 g Ca(NO 3 /1 mole Ca(NO 3 ) = 164 g Ca(NO 3 ) 2 8/30/18 Lab 2, Part 3 1 Report the % ethanol before you started your distillation See your Table 4 Ethanol Distillation Data 2 a Report the density of ethanol in g/ml from your 1st distillation b Report the % ethanol from your 1st distillation c Were you able to separate ethanol from water in the first distillation? Give reasons Compare the % ethanol before you started the distillation to the % ethanol from your first distillation If the % ethanol increased, then you were able to separate ethanol from water 3 a Report the density of ethanol in g/ml from your 2nd distillation b Report the % ethanol from your 2nd distillation c Were you able to separate ethanol from water in the second distillation? Give reasons Compare the % ethanol from your first distillation to the % ethanol from your second distillation If the % ethanol increased, then you were able to separate ethanol from water 4 If you did a 3rd distillation, would you expect the % ethanol to increase, decrease, or stay the same? Give reasons based on your answer to Questions 2b and 3b Compare the % ethanol before you started the distillation to the % ethanol from your first distillation to the % ethanol from your second distillation If the % ethanol increased from before distillation to the 1st distillation to the 2nd distillation, then you would expect the % ethanol to increase for a 3rd distillation These successive simple distillations are like doing a fractional distillation

14 If the % ethanol from before distilling to the first to the second distillation did not show a pattern, then you cannot draw a conclusion about the % ethanol for a 3rd distillation 8/28/18 Lab 2, Part 2 1 a Soda brand that you used in Lab 2 Example: Coca-Cola 1 b What is the % sugar according to the soda label from Lab 2? Give a number only; do not include text Example: 12 oz (355 ml) can of Coca-Cola contains 39 g of sugar % sugar = (mass of sugar/volume of soda) x 100 = (39 g sugar/355 ml soda) x 100 = 11% sugar 1 c What is the experimental % sugar from Lab 2? Give a number only; do not include text Measure known volume of soda into an empty beaker Heat soda to evaporate and separate the sugar from the rest of the soda Mass of sugar = mass of soda after heating - mass of beaker % sugar = (mass of sugar/volume of soda) x d What is the experimental % sugar from Lab 1? Give a number only; do not include text Calculate % sugar from mass of sugar per ml of soda from Lab 1 mass of sugar per ml of soda from Lab 1 = density of regular soda - density of diet soda This number tells you the mass of sugar in 1 ml of soda % sugar = (mass of sugar/volume of soda) x 100 Example: 105 g/ml density of regular soda g/ml density of diet soda = 010 g/ml This difference in density means there is 010 g of sugar in 1 ml of regular soda % sugar = (01 g sugar/1 ml of soda) x 100 = 10% sugar 1 e Calculate the % error in the % sugar in soda from Lab 1 % error = (true % sugar - experimental % sugar from Lab 1)/(true % sugar) x f Calculate the % error in the % sugar in soda from Lab 2 % error = (true % sugar - experimental % sugar from Lab 2)/(true % sugar) x g Which experiment, Lab 1 or Lab 2, was the better method to determine the mass of sugar in soda? Give reasons Compare the % error in % sugar for Lab 1 and Lab 2 The experiment that gave the smaller % error is closer (more accurate) to the true % error and is probably the better method 2 You measure the mass of an empty 250 ml beaker to be 1142 g You pour 100 ml of soda into this beaker; the mass of the beaker and soda is 2042 g You heat the soda and beaker in a 100 o C oven for 30 minutes The mass of the beaker and residue is 1234 g

15 a What is the mass of sugar in g? Give a number only; do not include text Mass of sugar = mass of beaker and residue - mass of beaker = 1234 g g = 92 g sugar b What is the % sugar in the soda? % sugar = (mass of sugar/volume of soda) x 100 = (92 g sugar/100 ml soda) x 100 = 92% sugar 8/23/18 Lab 2, Part 1 Problem 1: You find a fluid leak under your car The fluid is a colorless liquid Liquid A vinegar Liquid B NaCl (aq) Liquid C water Liquid D NaOH (aq) Problem 2: You are watching your favorite TV police drama The detective sees a white powdery substance, tastes it, Don't taste, Test! Solid 1 NaHCO 3 Solid 2 CaCO 3 Solid 3 NaCl Solid 4 sugar 8/21/18 Lab 1, Part 2 1 a What brand of soda did you use? b The experimental density of regular soda is g/ml Example: density of regular soda = 105 g/ml c The experimental density of diet soda is g/ml Example: density of diet soda = 095 g/ml d The volume of soda in your soda can or bottle is ml Examples: volume of soda can = 355 ml (12 oz) volume of soda bottle = 591 ml (20 oz) 2 Sugar is the ingredient that causes the difference in density a Calculate the difference in density between regular and diet soda in g/ml Difference in density = density of regular soda - density of diet soda Example: 105 g/ml g/ml = 010 g/ml This difference in density means there is 010 g of sugar in 1 ml of regular soda

16 b Calculate the mass of sugar in g in one can or bottle of soda based on the difference in density Mass of sugar = (density of regular soda - density of diet soda) x volume of soda Examples: In one 355 ml can of soda, the mass of sugar = 010 g/ml x 355 ml = 355 g In one 591 ml bottle of soda, the mass of sugar = 010 g/ml x 591 ml = 591 g c Report the mass of sugar in g in one can or bottle of soda from the label 12 oz (355 ml) can of Coca-Cola contains 39 g of sugar 20 oz (591 ml) bottle of Coca-Cola contains 65 g of sugar d Calculate the % error in the mass of sugar % error = (experimental value - true value)/true value x 100 Examples: 12 oz can of soda % error = (355 g - 39 g)/39 g x 100 = 9% error 20 oz bottle of soda % error = (591 g - 65 g)/65 g x 100 = 9% error 8/16/18 Lab 1, Part 1 1 a Based on class data, which volume measuring device is the most accurate? b Report the % error of each device to support your answer The most accurate volume measuring device shows the lowest % error % error = (experimental value - true value)/true value x 100 For 8-11 lab, 10 ml graduated cylinder data showed a 07% error and is the most accurate 50 ml beaker data showed a 11% error and is the 2nd most accurate 50 ml graduated cylinder data showed a 12% error and is the least accurate For 11-2 lab, 10 ml graduated cylinder data showed a 05% error and is the most accurate 50 ml beaker data showed a 1% error and is the 2nd most accurate 50 ml graduated cylinder data showed a 10% error and is the least accurate If you gave numbers only, you did not earn credit Match the device to the % error Eg, For the 50ml beaker, the %error is 1125%, for the 50ml GC, %error is 12%, and for the 10ml GC, %error is -07% c Based on class data, which volume measuring device is the most precise? d Report the % difference of each device to support your answer The most precise volume measuring device shows the lowest % difference % difference= (high value - low value)/average x 100 For 8-11 lab, 10 ml graduated cylinder data showed a 22% difference and is the most precise 50 ml graduated cylinder data showed a 71% error and is the 2nd most precise 50 ml beaker data showed a 20% error and is the least precise For 11-2 lab, 50 ml beaker and 50 ml graduated cylinder data showed a 0% difference and are the most precise 10 ml graduated cylinder data showed a 2% difference and is the least precise

17 If you gave numbers only, you did not earn credit Match the device to the % difference Eg, The % difference for the 50ml beaker is 20%, for the 50ml GC, % difference is 71%, and for the 10ml GC, % difference is 218% 2 a You calibrate a thermometer using boiling water as your calibration substance You record the temperature of boiling water as 971 degrees C When you use this thermometer to measure temperature, how many degrees should you add or subtract to your temperature reading? = 29 o C b You measure the temperature of water as 255 degrees C using the thermometer from Question 2a What is the actual temperature of the water in degrees C? From Question 2a, the thermometer reads 29 o C low So you want to add 29 o C to the measured temperature reading to give the actual temperature: = 284 o C 8/14/18, Lab 1, Day 1 1 a What does each line in ml on a 10 ml graduated cylinder represent? 01 ml b What is the uncertainty in volume when you use a 10 ml graduated cylinder? +/- 001 ml c You add enough water to the 5 ml mark on your 10 ml graduated cylinder You want to report the volume as ml 500 ml 2 Each line on a 100 ml graduated cylinder represents 1 ml What is the uncertainty in volume when you use a 100 ml graduated cylinder to measure volume? +/- 01 ml