chem 1212 final
When 5.22 g of CaCl2 dissolved in 50.00 mL of water in a coffee cup calorimeter, the temperature of the solution rose from 25.3°C to 28.9°C. Specific heat of the solution is equal to the specific heat of water = 4.18 J/gºC Density of the solution is equal to the density of water = 1.00 g/mL qsolution? qreaction? What is ΔHrxn in kJ/mol of CaCl2 ?
+ 831 J - 831 J - 17.7 kJ/mol
What is the oxidation number of C in C2O4−2 ?
+3
What is the oxidation number of S in HSO3− ?
+4
Match each item to its proper disposal method. - excess chemical - reaction mixture - used filter paper - cracker or chipped beaker
- appropriate waste container - appropriate waste container - trash can - broken glass box
Predict the initial rate (in kPa/sec) for Trial D using the data below. It was previously determined that the reaction is 1st order in D, 3rd order in E, and the average rate constant, k is equal to 0.280 kPa/(sec · M4). Enter your Initial Rate with 3 significant figures. Rate of reaction Ave. Init. Rate TRIAL [D] M [E] M (kPa/sec) A 0.300 0.400 5.40 x 10-3 B 0.300 0.200 6.83 x 10-4 C 0.600 0.400 1.05 x 10-2 D 0.200 0.600
.0121
What is the density of a solid that occupies a volume of 5.89 mL and weighs 5.14 g?
0.873g/mL
A 0.0455 g sample of sodium salicylate was dissolved and diluted to a final volume of 150 mL with deionized water. What is the concentration of the sodium salicylate solution?
1.895 x 10^-3
What is the pH of a 2.0 x 10-3 M HCl solution?
2.70
Using the sample data below, answer the questions below. E + D → B + A Rate of reaction Ave. Init. Rate TRIAL [D] M [E] M (kPa/sec) A 0.300 0.400 5.40 x 10-3 B 0.300 0.200 6.83 x 10-4 C 0.600 0.400 1.05 x 10-2 what is the reaction order of E what is the reaction order of D
3 1
What is the formula for hydrogen peroxide?
H2O2
Select the steps that will compose a rationale for the cation Mn+2 being absent in an unknown.
The lack of a purple-grape supernate over excess NaBiO3 in 3-G.
Which definition corresponds to aliquot?
a small portion of a chemical species
Select the step(s) that will compose a rationale for the cation Bi+3 being present in an unknown.
a white precipitate formed in step 2B, the white solid turned black upon adiditon of NaOH and SnCl2
A property of a solution that is dependent on the number of solute molecules in solution.
colligative property
What solution color will be observed at the end point in the buret?
dark blue
Select the appropriate word that matches the definition below. To carefully pour a liquid into another container.
decant
dentify the reaction type for the generic reaction given. ABC → AB + C
decomposition
For the error, indicate if the error will affect the mg of citric acid present per mL of juice, and if it does, will it raise or lower the value of the mg citiric acid/ mL of juice? Adding 20 mL of water to the Erlenmeyer flask before titration
no effect
In the reaction below, classify the chemical species as the type of electrolyte. Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + 2 H2O(ℓ) BaSO4
nonelectrolyte
What is the conductivity classification for an unknown F that dissolves completely in water and doesn't have any ions present in solution?
nonelectrolyte
Match the confirmation test with a description of the positive results Confirmation test for Mn+2 Confirmation test for Cr+3
purple solution pale yellow-tan solid
For the procedural error, indicate if the error will affect the actual yield of [Ni(C2H8N2)3]Cl2 product and if it does, will it raise or lower the actual yield: Did not rinse the product at all during filtration
raises the actual yield
Which definition corresponds to theoretical yield?
the amount of product that could be produced using a given amount of reactant
The partial pressure of solvent molecules in the gas phase at equilibrium.
vapor pressure
Cedrick & Astrid titrated a 20.00 mL aliquot of grapefruit juice with a 0.165 M NaOH solution to the end point. They calculated that there was 0.1457 g of citric acid present in the juice sample. What is the amount mg of citric acid present per mL of juice?
7.29mg/mL
A calibration plot of absorbance vs. concentration was obtained with standard solutions of sodium salicylate, which had a slope of the best-fit straight line as 1240 M-1. The absorbance of a dilute aspirin solution mixed with FeCl3 was 0.91. What is the concentration of the dilute aspirin solution?
7.34 x 10^-4 M
For the procedural error, indicate if the error will affect the actual yield of [Ni(C2H8N2)3]Cl2 product and if it does, will it raise or lower the actual yield: Left some product behind on the filter paper, not all on the watch glass
lowers the actual yield
For the procedural error, indicate if the error will affect the actual yield of copper(II) saccharinate product and if it does, will it raise or lower the actual yield: Spilling some of the copper(II) acetate while transferring the solid to the beaker
lowers the actual yield
For the procedural error, indicate if the error will affect the actual yield of copper(II) saccharinate product and if it does, will it raise or lower the actual yield: Washing the crystals with hot water
lowers the actual yield
Will under-titrating the end point in Part III affect the value of mg of Vitamin C?
lowers the value of mg Vitamin C
Will overtitrating the end point in Part II affect the value of Molarity of DCIP?
lowers the value of molarity of DCIP
What is the mole to mole ratio between Cu(C2H3O2)2·H2O and NaC7H4SO3N·H2O?
1 mol Cu(C2H3O2)2·H2O : 2 mol NaC7H4SO3N·H2O
What is the conductivity classification for an unknown H that only partially ionizes in water?
weak electrolyte
Match the confirmation test with a description of the positive results. Confirmation for Ag+ Confirmation for Pb+2
white precipitate yellow precipitate
In today's experiment, which chemical species is the acid-base indicator?
(C6H5OH)2C2O2C6H4 (phenolphthalein)
A coffee cup calorimeter contained 50.0 mL of a 1.33 M KOH solution at an initial temperature of 24.3 ºC. A student quickly add 35.0 mL of 1.42 M HNO3 to the calorimeter. The maximum temperature reached during the neutralization reaction was 29.1ºC. Determine the ΔHrxn for this neutralization reaction in kJ/mol of HNO3. assume specific heat of solution is the same as specific heat of water = 4.18 J/gºC assume density of both KOH and HNO3 are the same as water = 1.00 g/mL if negative value, be sure to type in a minus sign.
-34.3
What is the Molarity of the Ba(OH)2 solution if a 12.5 mL aliquot of the Ba(OH)2 solution required 17.50 mL of a 0.110 M H2SO4 solution to reach the equivalence point? Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + 2 H2O(l)
.154
In Experiment 6, Vitamin C (ascorbic acid) was titrated with dichloroindophenol (DCP) in a redox titration. But ascorbic acid, C6H8O6, can also be titrated in a redox titration with Br2(aq) solution as seen in the two half reactions below. Determine the overall reaction. C6H8O6 → C6H6O6 + 2 H+ + 2 e- Br2 + 2 e- → 2 Br- One vitamin C tablet was dissolved in a slightly acidic solution and titrated with 0.168 M Br2 using an ORP probe. The equivalence point of the titration curve was determined to be 17.8 mL. What is the mass (in grams) of Vitamin C, C6H8O6, in the tablet. (Enter your answer with 3 digits past the decimal) Molar Mass of C6H8O6 is 176.04 g/mol
.526
What is the average value of k (rate constant) for the data set below. Previously it was determined that the reaction was 1st order in E and 2nd order in D. Enter your value of k with 3 digits past the decimal. Rate of reaction Ave. Init. Rate TRIAL [E] M [D] M (kPa/sec) A 0.100 0.200 2.66 x 10-3 B 0.100 0.100 6.83 x 10-4 C 0.200 0.200 5.40 x 10-3
.674
What is the mole fraction (Χ) of CH3OH, methanol, in a solution of 8.50 mL of CH3OH and 4.53 g of C6H5COOH, benzoic acid ? Density of CH3OH is 0.792 g/mL Molar mass of CH3OH is 32.04 g/mol Molar mass of C6H5COOH is 122.12 g/mol
.850
Piers & Aida added 1.25 mL aliquot of H2O2 to a beaker containing 5.0 mL of 6 M H2SO4 and 90 mL of water. The hydrogen peroxide solution required 19.00 mL of 0.0225 M MnO4- to reach the equivalence point using the ORP probe. 5 H2O2(aq) + 2 MnO4-(aq) + 6 H+(aq) → 5 O2(g) + 2 Mn+2(aq) + 8 H2O(ℓ) What is the molarity of the original H2O2 solution?
.855
One tablet of generic aspirin was dissolved in 10 mL of 1.0 M NaOH and then diluted to 250 mL with deionized water. The sample was prepared by taking a 8.00 mL aliquot of this concentrated aspirin solution and diluting it to a final volume of 100.0 mL with FeCl3. A calibration plot determined that the diluted aspirin solution concentration was 5.907 x 10-4 M. What is the concentration (M) of the original aspirin solution?
0.00738
A reaction mixture was formed by adding 40 mL H2O, 8.00 mL of 0.44 M H2O2, and 7.0 mL of 0.70 M KI. What is the molarity of the H2 O2 in the reaction mixture? What is the molarity of the KI in the reaction mixture?
0.064 0.089
Vida & Mindy titrated a 10.00 mL aliquot of grapefruit juice to its endpoint and it used 14.87 mL of a 0.0981 M NaOH solution. Molar Mass of Citric acid (H3C6H5O7) = 192.12 g/mol H3C6H5O7(aq) + 3 NaOH(aq) → Na3C6H5O7(aq) + 3 H2O(l) how many grams o citric acid are present in their aliquot? what is the milligrams of citric acid per mL of juice?
0.09342g 9.34mg/mL
Ferris & Mona used the ORP sensor to titrate a ferrous ammonium sulfate solution, (NH4)2Fe(SO4)2 with KMnO4 titrant. They titrated a 8.50 mL aliquot of the Fe+2 solution with 0.0207 M MnO4- solution and determined that the equivalence point was at 12.3 mL. What is the molarity of the Fe+2 solution? 5 Fe+2(aq) + MnO4-(aq) + 8 H+(aq) → 5 Fe+3(aq) + Mn+2(aq) + 4 H2O
0.150M
Consider an experiment where 8.67 mL of an unknown H2O2(aq) solution reacted with the yeast at 20.4°C to produce 96.70 mL of gas. The barometric pressure was 775.3 torr. The vapor pressure of H2O is 17.5 torr at that temperature. What is the partial pressure of O2 (in atm) in the collected gas? How many moles of O2 were produced by the reaction? How many moles of H2O2 reacted to produce this amount of O2 ? What is the Molarity of the H2O2 solution?
0.9971 atm O2 0.004003 mol O2 0.008005 mol H2O2 .923 M H2O2
What is the pH of a 1.8 x 10-2 M NaOH solution?
12.26
What is the vapor pressure (in kPa) of ethanol, CH3CH2OH, over a solution which is composed of 22.50 mL of ethanol and 5.23 g of benzoic acid, C6H5COOH, at 35ºC ? Enter your number with two digits past the decimal. Pºethanol at 35ºC = 13.693 kPa Density of ethanol = 0.789 g/mL; Molar mass of ethanol = 46.07 g/mol Molar mass of benzoic acid = 122.12 g/mol
12.32
What is the vapor pressure (in kPa) of CH3OH, methanol, over a solution which is composed of 7.50 mL of methanol and 3.23 g of C6H5COOH, benzoic acid, at 25ºC ? Pº methanol at 25ºC = 16.915 kPa Density of methanol is 0.792 g/mL Molar mass of benzoic acid is 122.12 g/mol
14.80 kPa
Ozzie wanted to do another experiment with a stronger H2O2 solution to check the accuracy of the experiment by calculating the theoretical volume of O2(g) it would produce. Then he could compare his experimental volume of O2(g) to the theoretical volume of O2(g). He used 5.20 mL of 2.21 M H2O2 and the partial pressure of O2 was 0.9341 atm and the temperature was 298.35 K. What volume of O2(g) could he theoretically produce (in mL)?
150
Cedrick & Astrid titrated a 25.00 mL aliquot of grapefruit juice with a 0.117 M NaOH solution to the end point. The initial buret reading was 1.82 mL and the final buret reading was 21.33 mL. H3C6H5O7(aq) + 3 NaOH(aq) → Na3C6H5O7(aq) + 3 H2O(l) What is the volume of NaOH titrated? What is the mass of citric acid in the juice sample?
19.51mL of NaOH 0.146g of H3C6H5O7
A 7.50 mL aliquot of a 0.33 M HCl solution is diluted to a final volume of 50.00 mL. What is the molarity of this first dilution solution? Then a second dilution was made by taking 4.00 mL of the first dilution and diluting it to 25.00 mL. What is the molarity of this second dilution?
1st Dilution = 0.0495 M; 2nd Dilution = 7.92 x 10-3 M
Consider the half-reactions below and determine the overall reaction. Cu(s) → Cu+2(aq) + 2 e - Ag+(aq) + e - → Ag(s) How many electrons are transferred in the oxidation half-reaction? How many electrons are transferred in the reduction half-reaction? How many electrons are transferred in the overall reaction?
2 1 2
In a similar Exp. 9 experiment, a calibration plot of absorbance vs. concentration was obtained with the slope of the best-fit straight line as 1970 M-1. The diluted aspirin solution had an absorbance of 0.456. What is the concentration (M) of the aspirin in the dilute aspirin solution?
2.31 e-4
Ace, Corby & Astrid dissolved 0.0248 g of C6H8O6 in a 50.0 mL volumetric flask and filled it with deionized water to the mark. What is the Molarity of this standard solution of C6H8O6 ? Incorrect A 12.0 mL aliquot of the standard C6H8O6 above required 21.36 mL of DCP to reach the endpoint. Molarity of the DCP solution? A 10.00 mL aliquot of pear juice required 18.37 mL of the same DCP solution (from above) to reach the end point. How many mg of C6H8O6 are present in the aliquot?
2.82 x 10-3 M 1.58 x 10-3 M 5.12 mg
An 2.50 mL aliquot of 6.84 x 10-3 M sodium salicylate was diluted to a final volume of 500 mL with FeCl3 solution. What is the concentration of the dilute sodium salicylate solution?
3.42 x 10^-5 M
Ozzie wanted to do another experiment using 12.0% (by mass) H2O2. what is the molarity of this H2O2 solution?
3.53 M H2O2
Raoult's Law works for other units of pressure, such as atm, mmHg, and torr. The only requirement is that both vapor pressures have the same units. Predict the vapor pressure (in torr) of carbon tetrachloride, CCl4, over a solution which is composed of 325.0 g of CCl4 and 203.4 g of I2 at 65ºC. Submit your answer with 1 digit past the decimal. PºCCl4 at 65ºC = 531 torr Molar mass of CCl4 is 153.81 g/mol Molar mass of I2 is 253.8 g/mol
384.98
What is the pH of a buffer in which the concentration of benzoic acid, C6H5COOH, is 0.075 M and the concentration of sodium benzoate, NaC6H5COO, is 0.050 M ? Ka of C6H5COOH is 6.30 x 10-5
4.02
Ethyl, Ann & Ami reacted 3.50 g of NiCl2·6 H2O with 12.00 mL of 4.00 M C2H8N2. They recovered 2.31 g of product, (Ni(C2H8N2)3)Cl2. the theoretical yield of the product is... the percent yield of the product is...
4.56g 50.6%
What is the pH of a solution that has 0.060 M CH3COOH and 0.040M NaCH3COO present? Ka for acetic acid = 1.80 x 10-5
4.57
One tablet of generic aspirin was dissolved in 10 mL of 1.0 M NaOH and then diluted to a final volume of 250 mL with deionized water. A 7.50 mL aliquot of this concentrated aspirin solution was diluted to a final volume of 125 mL with FeCl3. From previous calculations by your partner, the dilute solution was found to be 5.71 x 10-4 M and the original, concentrated solution was determined to be 9.51 x 10-3 M. How many mg of aspirin are present in one tablet of the aspirin?
428
Zach and Nate calculated the theoretical yield as 7.11 g of Cu(C7H4SO3N)2(H2O)4·2 H2O. They recovered 4.35 g of Cu(C7H4SO3N)2(H2O)4·2 H2O. What is the percent yield?
61.2%
Pierce, Manny & Ada worked together on the redox titration of H2O2 with MnO4- (Part II). Pierce & Manny used the equivalence point volume of MnO4- as determined from titration graph. However, Ada used the volume of MnO4- when the solution was dark pink, which was a larger volume than Pierce & Manny's volume. Will Ada's calculations of the molarity of H2O2 be different than Pierce & Manny's calculation? How and why?
Ada's M of H2O2 will be higher than the other two students. Since the volume of MnO4- is in the numerator for the calculation of M of H2O2, the higher volume of MnO4- results in higher M of H2O2.
You have two test tubes. One test tube contains Ag+(aq) solution and the other test tube contains Bi+3(aq). Predit what will happen when HCl(aq) is added to both test tubes. If a reaction occurs, what is the new chemical fomula?
Ag+ (aq) will form a white precipitate, AgCl(s). Bi+3 (aq) will remain unchanged.
Separation can be achieved when a reaction occurs in a mixture. The resulting mixture will have one chemical species in a solution and the other chemical species as a solid. The mixture is centrifuged and the supernate is decanted into a separate test tube. Now the two chemical species (solid and solution) are separated from each other. What reagent could you add to a mixture of [Zn(OH)4]-2(aq) and CrO4-2(aq) to separate the two species?
BaCl2
Match the correct inference to the description of the reactions from the Group 1 & 2 Qualitative Analysis Experiment. In step 2-B, after adding the 15 M NH3' the solution tested as basic and the light blue solution had turned dark blue. No solid formed. In step 2-D, after adding the CH3COOH, the solution tested as acidic and the dark blue solution turned light sky blue. Then after adding K4Fe(CN)6 in step 2-E, a reddish-brown precipitate formed. In step 1-A after adding the 6 M HCl to an unknown, no precipitate formed and a light blue solution remained unchanged
Bi+3 is confirmed as absent. Cu+2 is confirmed as present Ab+ and Pb+2 are confirmed as absent
In today's experiment, which chemical species is the analyte?
C6H8O6 (ascorbic acid or vitamin C)
You have two test tubes. One test tube contains Cr+3(aq) solution and the other test tube contains Ni+2(aq). Predict what will happen when NaOH(aq) is added to both test tubes. If a reaction occurs, what is the new chemical formula?
Cr+3(aq) will form a green solution, [Cr(OH)4]- (aq). Ni+2(aq) will form a green precipitate,Ni(OH)2 (s).
In this reaction, you observed several different Cu species which had different physical attributes. Select the appropriate chemical formula(s) that corresponds to a red-brown solid.
Cu
In this reaction, you observed several different Cu species which had different physical attributes. Select the appropriate chemical formula(s) that corresponds to a turquoise (blue-green) solid.
Cu(OH)2
An experimental method to estimate the density of a crystal is to compare it to a variety of solution of known densities. Solution K (density = 1.5 g/mL), Solution L (density = 1.2 g/mL) and Solution W (density = 1.0 g/mL) are poured into a test tube. The liquids are immiscible with each other and solid M is insoluble in each. When a few crystals of M are added to the test tube, it sinks through solutions W & L, but floats on top of solution K. What is the best approximate density of solid M?
Density of M is greater than 1.2 g/mL but less than 1.5 g/mL.
You have two test tubes. One test tube contains Fe+3(aq) solution and the other test tube contains Cr+3(aq). Predict what will happen when NaOH(aq) is added to both test tubes. If a reaction occurs, what is the new chemical formula?
Fe+3(aq) will form a brown precipitate, Fe(OH)3(s). Cr+3(aq) will form a green solution, [Cr(OH)4 ]-(aq).
Which chemical(s) used in this experiment is/are toxic?
H2SO4, NaOH
Separation can be achieved when a reaction occurs in a mixture. The resulting mixture will have one chemical species in a solution and the other chemical species as a solid. The mixture is centrifuged and the supernate is decanted into a separate test tube. Now the solid and solution are separated from each other. What reagent could you add to a mixture of Ag+ and Cu+2 to separate the two species?
HCl
Which statements explain the shape of the titration curve observed in lab? I. Initially, the conductivity is zero since the reaction has not begun. II. During the reaction, the conductivity decreases due to the decrease of Ba+2 and OH- ions present. III. After the endpoint, the conductivity stays at the same level since no more reaction occurs. IV. At the equivalent point, the conductivity is nearly zero since all the Ba+2 and OH- ions have reacted to produce nonelectrolyte products.
II and IV are TRUE
From the description of the reaction below, balance the equation and also select the classification of the reaction. When green soluiton of Ni(NO3)2 (aq) reacts with a colorless solution of KOH (aq), it forms a lime-green precipitate and a colorless solution of KNO3 (aq) over the solid. ___KOH (aq) + __Ni(NO3)2 (aq) → __KNO3 (aq) + _Ni(OH)2 (s) coefficient in front of KNO3 (aq) coefficient in front of Ni(NO3)2 (aq) coefficient in front of Ni(OH)2(s) coefficient in front of KOH (aq) classification of reaction
KNO3: 2 Ni(NO3)2: 1 Ni(OH)2: 1 KOH: 2 reaction: double displacement
Liquid A is immiscible with Liquids B & C. Liquid B is immiscible with Liquid C. The liquids were poured into the beaker in order of increasing density. beaker with 3 colored layers Select the appropriate label for each layer. Compound Mass (g) Volume (mL) Liquid C 28.1 20.0 Liquid A 21.8 20.0 Liquid B 9.2 10.0 Which chemical species is at the bottom? Which chemical species is in the top layer? Which chemical species is in the middle layer?
Liquid C- bottom layer Liquid B- top layer Liquid A- middle layer
Separation can be achieved when a reaction occurs in a mixture. The resulting mixture will have one chemical species in a solution and the other chemical species as a solid. The mixture is centrifuged and the supernate is decanted into a separate test tube. Now the two chemical species (solid and solution) are separated from each other. What reagent could you add to a mixture of Fe+3(aq) and Zn+2(aq) to separate the two species?
NaOH
Which chemical(s) will be in the buret?
NaOH
In the generic reaction below, experimental data indicate the reaction is second order in A, first order in C and rate constant is 5.4 x 10 -3 M -2sec -1. Which is the correct rate constant expression? A(aq) + 2 C(aq) → AC2(aq)
Rate = (5.4 x 10 -3 M -2sec -1) [A] 2 [C]
What is the correct definition of specific heat?
The amount of heat required to change the temperature of one gram of substance by 1°C.
Consider the benzoic acid dissociation reaction below which is at equilibrium. C6H5COOH (aq) + H2O(ℓ) ⇋ C6H5COO-aq) + H3O+(aq) If some strong base is added (the hydroxide ion which removes H3O+) is added to the system (stress), how will the system change in order to re-establish equilibrium? Select all that might apply.
The concentration of C6H5Coo will increase the concentration of C6H5COOH will decrease
If an error caused the final temperature to be larger, how does this affect the calculation of the heat of solution (qsolution)?
The larger Tfinal would produce a larger ΔT, which would result in a larger q.
Iggy, Lee & Brianne planned a new experiment based on two reactions involving Cu complexes they had previously observed in Exp. 11 & 12. [Cu(H2O)4]+2 (or simply as Cu+2) is a sky blue solution and [Cu(NH3)4]+2 is a dark royal blue solution. [Cu(H2O)4]+2(aq) + 4 NH3(aq) ⇋ [Cu(NH3)4]+2(aq) + 4 H2O(ℓ) Make a hypothesis on what will occur in the equilibrium system (initially a medium blue solution) if the reaction is exothermic and it is placed in cold water bath. Then explain what will occur in terms of Le Châtelier's principle.
The solution will become a darker blue solution. The system must shift towards products to generate heat (a product) that was lost.
What will result when liquid W (density = 0.75 g/mL), liquid S (density = 0.65 g/mL, immiscible with liquid W), and liquid T (density = 0.85 g/mL, miscible with liquid W and immiscible with liquid S) are poured into test tube?
Two layers will form in the test tube. The top layer is liquid S and the bottom layer is a mixture of liquid W & T.
Predict the equilibrium shifts that will occur in the endothermic equilibrium reaction below in order to re-establish equilibrium. CH4(g) + H2O(g) ⇋ CO(g) + 3 H2(g) Increasing the partial pressure of carbon monoxide gas Decreasing the overall total pressure of the equilibrium system
Will shift the equilibrium towards the reactants will shift the equilibrium towards the products
Select the step(s) that will compose a rationale for the cation Zn+2 being present in an unknown.
a grey white solid formed in step 3J
Match the confirmation test with a description of the positive results. Confirmation test for Cu+2 Confirmation test for Bi+3
a maroon precipitate a black solid
Select the step(s) that will compose a rationale for the cation Cu+2 being absent in an unknown.
a reddish brown precipitate did not form after adding K4Fe(CN)6
Select the correct definition or example of the following terms: Bronsted Lowry acid Acidic buffer Buffering Capacity
any substance that donates a proton a mixture of a weak acid and the salt of its conjugate base the amount of acid or base that can be added before the pH changes 1 pH unit
NH3 (aq) and NH4OH (aq) are different ways of writing the chemical formula of the which chemical ?
aqueous ammonia
Select all the statements that are true concerning pH and buffers.
as an acidic solution is diluted the pH increases the greater the concentrations of the buffer components, the greater is buffering capacity
Consider the equilibrium reaction below. At high concentrations of HA the solution will be blue; but at low concentrations of HA the solution will be red. Initially the equilibrium mixture below is purple (combination of red & blue). What color is expected after adding some colorless A-(aq) to the equilibrium solution? A-(aq) + H2O(ℓ) ⇋ HA(aq) + OH-(aq)
blue
Consider the exothermic equilibrium system below. The [CuCl4]-2(aq) ion is light green while the [CuBr4]2(aq) ion is dark brown. Originally the equilibrium below was a dark green. [CuCl4]-2(aq) + 4 Br-(aq) ⇋ [CuBr4]-2(aq) + 4 Cl-(aq) Predict the color of the solution after the system has re-established equilibrium. Placing the system in an ice-bath for 10 minutes. Adding a few drops of Ag+(aq) solution (Ag+ reacts with Cl- ions).
brown solution brown solution
Identify the reaction type for the generic reaction given. A + B → AB
combination
For the following error, select the answer that correctly describes how it will affect the value of the final temperature of the water/solution in the calorimeter: Dropping the hot aluminum rod and it remains on the cold lab bench for 30 seconds before it is successfully added to the calorimeter.
decreases the value of final temperature
Select all that apply to an endothermic reaction.
heat is a reactant removing heat ( cold water bath) will cause the equilibrium to shift toward reactants
You have one test tube which contains a white solid that is either AgCl (s) or PbCl2 (s). Select a reagent that will allow you to differentiate between the two chemical species. If the solid is AgCl, what will happen when the reagent is added? If the solid is PbCl2, what will happen when the reagent is added?
hot water If it is AgCl, the white solid will remain the same after adding the hot water. If it is PbCl2, the solid will dissolve and form a colorless solution after adding the hot water.
Callie, Gay, & Steve were discussing the results of this experiment in terms of general trends. Which statement below is TRUE ?
if the volume of the solvent was constant, as more solute was added, the Psolvent decreased
In this experiment, you will be using and measuring various chemical species by a variety of units. Which units of measure is used for the temperature of water?
kelvin
In this experiment, you will measure the temperature of the water, which is also the temperature of the gas that is captured in the graduated cylinder. Before doing calculations, the temperature must be converted to what unit of measure?
kelvin
Nick and Kel reacted 3.25 g of NiCl2· 6 H2O with 12.00 mL of 4.00 M C2H8N2. They recovered 3.43 g of product, [Ni(C2H8N2)3] Cl2. At the end, the filtrate was a light pink solution. The litmus test on the filtrate solution turned the red litmus paper blue in color where the solution touched the paper. NiCl2· 6 H2O + 3 C2H8N2 → [Ni(C2H8N2)3]Cl2(s) + 6 H2O Molar Mass of NiCl2· 6 H2O is 237.69 g/mol Molarity of C2H8N2 is 4.00 M Molar Mass of product, [Ni(C2H8N2)3]Cl2(s) is 309.90 g/mol Based on the experiment described, select the correct answers for the questions below. the chemical NiCl2 · 6H2O is the... the chemical, C2H8N2 is the... The actual or experimental yield is... the theoretical yield is...
limiting reagent chemical present in exess 3.43g 4.24g
Match the correct definition or example to each item. rate constant expression rate determining step
mathematical expression showing the relatiosnhip between the measured rate and the concentration of the reactants step in the reaction mechanism that has the slowest rate
A common error in titration is over-titrating. Which of the following statement(s) is/are TRUE? I. Over-titrating means too much titrant was added to the reaction. II. Since the volume of titrant is too large, dividing by a larger number in the calculation of citric acid making the mass of citric acid be too low. III. Over-titrating means too much aliquot was added to the reaction.
only I is true
What is the name of KSCN ?
potassium thiocyanate
Select the appropriate word that matches the definition below. A solid compound that forms as a result of mixing reagents together in a solution.
precipitate
For the error, indicate if the error will affect the mg of citric acid present per mL of juice, and if it does, will it raise or lower the value of the mg citiric acid/ mL of juice? Over-titrating the end point (adding too much titrant)
raises the value of mg citric acid/mL juice
MgSO4(s) disappears when added to water(ℓ) and stirred. What describes the relationship between MgSO4 and water?
soluble
In the redox reaction below, identify and match each reactant to their function. 3 CH3CH2OH (aq) + 2 Cr2O7−2 (aq) + 16 H+(aq) → 3 CH3CO2H (aq) + 2 Cr+3(aq) + 11 H2O(aq) CH3CH2OH (aq) Cr2O7−2 (aq)
species being oxidized species being reduced
Select the redox term(s) that apply to Mn in MnO4 - in the half reaction below. MnO4 - (aq) + 4 H+(aq) + 3 e - → MnO2 (s) + 2 H2O
species being reduced oxidizing agent
In the reaction below, classify the chemical species as the type of electrolyte. Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + 2 H2O(ℓ) Ba(OH)2
strong electrolyte
Predict the conductivity of NaNO3, a soluble, ionic compound.
strong electrolyte
In a certain reaction, a solid chemical dissolved in water. The temperature of the water sample dropped from 27.3 °C to 22.4 °C. From this description of the experiment, select the correct words to fill the blanks. The water is defined as the _______ The system _____ heat qsystem has a __________ value the reaction is an _____________ reaction
surroundings gained positive endothermic
Which definition corresponds to an analyte?
the chemical species of interest
Which definition corresponds to excess reagent?
the reactant that is present as extra material when the reaction is complete
In a similar experiment, Cooper, Zach & Nate started with 4.18 g of Cu(C2H3O2)2·H2O and 9.78 g of NaC7H4SO3N·H2O and obtained 10.84 g of Cu(C7H4SO3N)2(H2O)4·2H2O. theoretical yield? percent yield?
theoretical: 11.21g percent yield: 96.7%
In this experiment, you will be using and measuring various chemical species by a variety of units. Which units of measure is used for the vapor pressure of water?
torr
What should you do if some NaOH comes into contact with your skin?
wash skin for 15 minutes and notify TA
What should you do if some of the H2O2-H2SO4 solution comes into contact with your skin?
wash the skin for 15 minutes w/ water and notify TA
Predict the conductivity of NH2(CH3), a weak base.
weak electrolyte
What is the conductivity classification for an unknown A that dissolves completely in water and partially dissociates into ions?
weak electrolyte
Predict the equilibrium shifts that will occur in the endothermic equilibrium reaction below in order to re-establish equilibrium. CH4(g) + H2O(g) ⇋ CO(g) + 3 H2(g) Increasing the overall volume (decreasing the overall pressure) of the equilibrium system. Increasing the overall temperature of the equilibrium system.
will shift the equilibrium towards the products will shift the equilibrium towards the products
Askor & Bich found that it required 23.14 mL of 1.32 x 10-3 M DCIP solution to reach the endpoint when titrating a 7.50 mL aliquot of pear juice. C6H8O6(aq) + C12H7O2NCl2(aq) → C6H6O6(aq) + C12H9O2NCl2(aq) C12H7O2NCl2 is abbreviated as DCIP Molar Mass of C6H8O6(s) is 176.14 g/mol Daily Recommended Intake (DRI) for adults: 90 mg of Vitamin C How many mg of ascorbic acid, C6H8O6, are present in the juice aliquot ? How many mL of this juice would Bich have to drink in order to meet the Daily Recommended Intake (DRI) ?
5.38mg 126mL
Cooper, Zach and Nate did this experiment dissolving 3.65 g of Cu(C2H3O2)2·H2O and adding 8.25 g NaC7H4SO3N·H2O (assume present in excess). What is the theoretical yield of the product, Cu(C7H4SO3N)2(H2O)4·2 H2O(s)? Molar Mass of Copper(II) acetate monohydrate = 199.65 g/mol Molar Mass of Sodium saccharinate monohydrate = 223.18 g/mol Molar Mass of product = 535.59 g/mol
9.79g
Separation can be achieved when a reaction occurs in a mixture. The resulting mixture will have one chemical species in a solution and the other chemical species as a solid. The mixture is centrifuged and the supernate is decanted into a separate test tube. Now the solid and solution are separated from each other. What reagent could you add to a mixture of Pb+2 and Bi+3 to separate the two species?
HCl
You have one test tube which contains a solution that is either Ni+2 (aq) or Fe+3 (aq). Select a reagent that will allow you to differentiate between the two chemical species. If the solution is Ni+2 (aq), what will happen when the reagent is added? If the solution is Fe+3 (aq) what will happen when the reagent is added?
NaOH If it is Ni+2(aq), a green precipitate will form after adding the NaOH. If it is Fe+3 (aq), a gold-brown precipitate will form after adding the NaOH.
You have one test tube which contains a solution that is either Zn+2(aq) or Fe+3(aq). Select a reagent that will allow you to differentiate between the two chemical species. If the solution is Zn+2(aq), what will happen when the reagent is added? If the solution is Fe+3(aq), what will happen when the reagent is added?
NaOH If it is Zn+2(aq), the solution will stay colorless after adding the NaOH. If it is Fe+3(aq), the gold-brown precipitate will form after adding the NaOH.
Match the correct inference to the descriptions of the reactions from the Group 3 Qualitative Analysis Experiment, A light sky blue solution formed after adding 6 M NH3 in step 3-E A yellow-tan precipitate formed in step 3-H when BaCl2 was added. When the yellow K4Fe(CN)6 solution was added in step 3-J, no precipitate formed. After the NaOH is added in step 3-H, the decantate solution is green.
Ni+2 is indicated as present Cr+3 is confirmed as present Zn+2 is confirmed as absent Cr+3 is indicated
Which statement best explains what happens to the percent yield if the crystals (product) were washed with hot water?
actual yield decreases since part of theproduct will dissolve and not be recovered as a solid since actual yield is in the numerator, the percent yield will also decrease
Sal, Liz and Nate did the Determination of Aspirin experiment together since Liz's partner, Astrid was absent. Astrid took the data from the group and graphed the calibration data of the absorbances of the dilute sodium salicylate solutions versus the molarity of these solutions. Astrid's plot had a slope of 1750 M-1 while Sal, Liz & Nate's plots had a slope of 1680 M-1. Which statement(s) is/are TRUE about any effects the different slopes will have on the calculations of the concentration of the aspirin solutions?
astrid's concentration of the dilute aspirin solution will have smaller value than Sal's the molarity value of Astrid's concentrated aspirin solution will be smaller than Nate's
Match the confirmation test with a description of the positive results. Confirmation test for Fe+3 Confirmation test for Ni+2
blood red solution red-pink precipitate
The process of molecules escaping the liquid phase to go into the gas phase.
evaporation
Which of the following statements are TRUE if the titration of fruit juice (Part III) was under-titrated? I. The amount of Vitamin C will be lower since the smaller volume of DCIP is in the numerator in the Vitamin C calculation. II. Too little DCIP was added in the titration, causing the Molarity of the ascorbic acid to be lowered. III. The amount of Vitamin C would be higher since under-titrating makes the Molarity of DCIP higher and the Molarity of DCIP is in the numerator of the Vitamin C calculation.
only I is true
Piers & Aida performed this experiment. Aida read the initial volume of hydrogen peroxide as 7.5 mL, but Piers read the volume as 8.5 mL. Which of the following statement(s) are TRUE about Piers' calculations? I. Piers' calculations will give a higher value of moles of O2(g) than Aida. II. Piers' calculations will give a higher partial pressure of O2(g) than Aida. III. Piers' calculations will give a lower molarity of H2O2 than Aida.
only III is true
Cooper and Zach did this experiment dissolving 3.55 g of Cu(C2H3O2)2·H2O and adding 7.94 g NaC7H4SO3N·H2O. They recovered 8.25 g of product. In their calculations, they found that 9.52 g of product should be produced. Their calculation of (8.25 g/9.52 g) x 100% is equal to 86.6 %. what is the percent yield? theorhetical yield? actual yield?
percent yield; 86.6 theoretical: 9.52 actual: 8.25
What color is expected for the product, [Ni(C2H8N2)3]Cl2, if C2H8N2 is the limiting reagent?
pink-violet