Chem 1212 Midterm
Which of the following items of clothing are appropriate to wear in CHEM 1212 Lab to protect your skin ? Select all that apply. 1. Scrub pants 2. Jeans 3. Lab Apron 4. Knee length shorts 5. Leggings 6. Tank top 7. Midriff top 8. T-shirt
T-shirt, Scrub pants, Lab apron, Jeans
If two liquids do not mix completely, they will form layers. Then the liquids are described as _____________. An example of ________________mixture is the combination of olive oil and vinegar in an oil vinaigrette for salad
immiscible
(Experiment 8): In this experiment, you will measure the volume of the oxygen. Before doing calculations, the volume must be converted to what unit of measure? Select one: Kelvin liter Celsius milliliter
liter
When two liquids mix completely with each other, they are ________________.
miscible
(Experiment 8): In this experiment, you will be using the gas constant, R. Which unit is NOT found in R? Select one: atmosphere liter Kelvin molarity
molarity
What is the Molarity of the Ba(OH)2 solution if a 7.50 mL aliquot of the Ba(OH)2 solution required 14.30 mL of a 0.108 M H2SO4 solution to reach the equivalence point? Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + 2 H2O(l) Type your answer in the box with 3 digits past the decimal.
0.206
(Experiment 6): In today's experiment of determining the amount of Vitamin C in fruit juice, which chemical species controls the pH of the solution? Select one: 1. (HPO3)n (metaphosphoric acid) 2. C6H8O6 (ascorbic acid or Vitamin C) 3. C12H7O2NCl2 (2,6-dichloroindophenol or DCIP)
1. (HPO3)n (metaphosphoric acid)
Match each item to its proper disposal method. Answers be used more than once. 1. Excess chemical --> 2. Reaction mixture --> 3. Used filter paper --> 4. Cracked or broken beaker -->
1. Appropriate waste container 2. Appropriate waste container 3. Trash can 4. Broken glass box
(Experiment 3): In this reaction, you observed several different Cu species which had different physical attributes. Select the appropriate chemical formula(s) that corresponds to a sky blue solution. Select one or more: 1. CuSO4 2. CuO 3. Cu 4. Cu(OH)2
1. CuSO4
(Experiment 5): In today's experiment, the fruit juice contains what chemical species? Select one: 1. H3C6H5O7 (citric acid) 2. H2O 3. (C6H5OH)2C2O2C6H4 (phenolphthalein) 4. NaOH
1. H3C6H5O7 (citric acid)
Sid Trick titrated a 15.0 mL aliquot of juice. It required 18.23 mL of 0.0998 M NaOH to reach the equivalence point. Analyze his results and answer the questions below. The reaction and the molar mass are given below. H3C6H5O7(aq) + 3 NaOH(aq) → Na3C6H5O7(aq) + 3 H2O(ℓ) Molar Mass of H3C6H5O7 = 192.12 g/mL 1. How many grams of citric acid were present in the aliquot? 2. How many mg of citric acid were present per mL of juice?
1. How many grams of citric acid were present in the aliquot? 0.116g 2. How many mg of citric acid were present per mL of juice? 7.77mg/mL
(Experiment 5): 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: Added an extra 5 mL of acetone in step 7 of Part II Select one: 1. No effect 2. Lowers the actual yield 3. Raises the actual yield
1. No effect
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 Select one: 1. No effect 2. Raises the value of mg citric acid/mL juice 3. Lowers the value of mg citric acid/mL juice
1. No effect
Will use of a higher Molarity value of ascorbic acid affect the calculated Molarity of DCIP? Select one: 1. Raises the value of Molarity of DCIP 2. Lowers the value of Molarity of DCIP 3. No effect
1. Raises the value of Molarity of DCIP
Nick and Kel reacted 2.80 g of NiCl2· 6 H2O with 7.00 mL of 4.00 M C2H8N2. They recovered 2.40 g of product, [Ni(C2H8N2)3] Cl2. At the end, the filtrate was a dark blue solution. The litmus test on the filtrate solution left the red litmus paper unchanged in color. 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. 1. The chemical, NiCl2· 6 H2O, is the__________. 2. The theoretical yield is ___________. 3. The actual or experimental yield is ___________. 4. The chemical, C2H8N2, is the ____________.
1. The chemical, NiCl2· 6 H2O, is the chemical present in excess. 2. The theoretical yield is 2.89g 3. The actual or experimental yield is 2.40 4. The chemical, C2H8N2, is the limiting reagent.
In a similar experiment, Cooper, Zach & Nate started with 2.85 g of Cu(C2H3O2)2·H2O and 6.77 g of NaC7H4SO3N·H2O and obtained 6.17 g of Cu(C7H4SO3N)2(H2O)4·2H2O. 1. The theoretical yield of the product is _________. 2. The percent yield of the product is ____________. 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
1. The theoretical yield of the product is 7.65 2. The percent yield of the product is 80.7% To find the theoretical yield, Calculate moles of Cu(acetate)2 monohydrate Use that number and the mole:mole ratio, to find moles of product Calculate mass of product (theoretical yield) using previous number & Molar mass of product To find % yield, divide the actual yield by the theoretical yield, and multiply by 100%
Here is useful information for the questions below. Select your answers from the pull-down menus. C12H7O2NCl2 is abbreviated as DCIP Molar Mass of C6H8O6(s) is 176.14 g/mol C6H8O6(aq) + C12H7O2NCl2(aq) → C6H6O6(aq) + C12H9O2NCl2(aq) Ace, Corby & Astrid dissolved 0.0531 g of C6H8O6 in a 50.0 mL volumetric flask and filled it with deionized water to the mark. 1. What is the Molarity of this standard solution of C6H8O6 ? A 5.00 mL aliquot of the standard C6H8O6 above required 14.38 mL of DCIP to reach the endpoint. 2. What is the Molarity of the DCIP solution? A 15.00 mL aliquot of pear juice required 15.47 mL of the same DCIP solution (from above) to reach the end point. 3. How many mg of C6H8O6 are present in the aliquot?
1. What is the Molarity of this standard solution of C6H8O6 ? 6.03e-3 2. What is the Molarity of the DCIP solution? 2.10e-3 3. How many mg of C6H8O6 are present in the aliquot? 5.71mg Molarity of C6H8O6 = (mass C6H8O6 / Molar Mass C6H8O6) / total volume in L Molarity of DCIP = {M C6H8O6 (from above) x L C6H8O6 (aliquot) x (1 mol DCIP/1 mol C6H8O6) } / L of DCIP titrated mg of C6H8O6 in juice = M DCIP (from above) x L of DCIP titrated x (1 mol C6H8O6/1 mol DCIP) x Molar Mass C6H8O6 x (1000 mg/1 g)
Consider an experiment where 7.50 mL of an unknown H2O2(aq) solution reacted with the yeast at 22.3°C to produce 82.34 mL of gas. The barometric pressure was 764.8 torr. The vapor pressure of H2O is 19.8 torr at that temperature. 1. What is the partial pressure of O2 (in atm) in the collected gas? 2. How many moles of O2 were produced by the reaction? 3. How many moles of H2O2 reacted to produce this amount of O2 ? 4. What is the Molarity of the H2O2 solution?
1. What is the partial pressure of O2 (in atm) in the collected gas? 0.9803 atm 2. How many moles of O2 were produced by the reaction? 0.003329 mol 3. How many moles of H2O2 reacted to produce this amount of O2 ? 0.006658 4. What is the Molarity of the H2O2 solution? 0.888
MgSO4(s) disappears when added to water(ℓ) and stirred. What describes the relationship between MgSO4 and water? Select one: 1. soluble 2. insoluble 3. miscible 4. immiscible
1. soluble
Cooper and Zach did this experiment dissolving 3.10 g of Cu(C2H3O2)2·H2O and adding 6.93 g NaC7H4SO3N·H2O. They recovered 6.28 g of product. In their calculations, they found that 8.32 g of product should be produced. Their calculation of (6.28 g/8.32 g) x 100% is equal to 75.5%. 1. What is the theoretical yield ? 2. What is the percent yield ? 3. What is the actual yield ?
1. theoretical yield= 8.32 2. percent yield= 75.5 3. actual yield= 6.28
A 84.0 mg sample of Red 40 dye was dissolved and diluted to a final volume of 0.750 L with deionized water. What is the concentration of the Red 40 dye solution in ppm? parts per milliion (ppm) refers to 1 mg of solute in 1.0 L of solution; (mg/L) Select one: 112 ppm 44.8 ppm 0.0089 ppm 2.80 ppm
112 ppm
A calibration plot of absorbance vs. concentration (ppm) was obtained with standard known Red 40 dye solutions. The slope of the best-fit straight line of the plot is 0.057 ppm- 1 The absorbance of the dilute unknown sports drink was 0.88 What is the concentration of this dilute unknown sports drink ? Select one: 15.4 ppm 5.02 ppm 64.8 ppm 19.9 ppm
15.4 ppm
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 3.18 M H2O2 and the partial pressure of O2 was 0.9959 atm and the temperature was 291.25 K. What volume of O2(g) could he theoretically produce (in mL)? Enter your answer to 3 significant figures.
198 This question is just working the calculations in reverse from the lab. There are three parts to the calculations. Using Molarity and mL of H2O2 find moles of H2 O2 By stoichiometry find moles of O2 (g) By Ideal Gas Law find Volume of O2 Part 1. Find moles of H2O2 Molarity H2O2 x mL H2O2 x 1L/1000 mL = mol of H2O2 Part 2. Find moles of O2(g) moles H2O2 (from above) x 1 mol O2/2 mol H2O2 = mol O2 (from the balanced reaction) Now that you have moles of O2 gas you can use the Ideal Gas Law. The H2O2 data is aqueous, so you can't use gas law calculations for solutions! Part 3. Find Volume of O2(g) Use R = 0.08206 L atm/K mol and the PV=nRT ; Rearrange PV=nRT to solve for V since you have R, PO2 ,T, mol of gas (which is n) V = (nRT/P) Finally convert to mL of O2 The correct answer is: 198
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: Leaving some crystals behind in the beaker Select one: 1. No effect 2. Lowers the actual yield 3. Raises the actual yield
2. Lowers the actual yield
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? Not dividing the mg of citric acid by the volume of juice Select one: 1. No effect 2. Raises the value of mg citric acid/mL juice 3. Lowers the value of mg citric acid/mL juice
2. Raises the value of mg citric acid/mL juice
Which definition corresponds to excess reagent? Select one: 1. A small portion of a chemical species. 2. The reactant that is present as extra material when the reaction is complete. 3. The amount of product that could be produced using a given amount of reactant. 4. A chemical species that contains a metal ion that is coordinated to ligands. 5. The reactant that is completely consumed during the reaction.
2. The reactant that is present as extra material when the reaction is complete.
Ozzie wanted to do another experiment using 8.75% (by mass) H2O2. What is the Molarity of this H2O2 solution ? __________ H2O2
2.57 In the last step of the calculations we did in the lab, we converted Molarity of H2O2 into % by mass by the equation below. For this problem, we need to work it in the reverse. % (by mass) = Molarity H2O2 x Molar Mass × (1 / (Density) × (1 L/1000 mL) × 100% *we assumed the density of water and the hydrogen peroxide solution were both 1.0 g/mL since the solution is mostly water). However, this time start with the % and convert it to Molarity by rearranging the equation above. Molarity = % (by mass) / 100 x Density × (1/Molar mass) x (1000 mL/1L) Now substitution the definition of % (by mass) into the equation above. % (by mass) = (mass of H2O2/ mass of solution) Molarity = [(g of H2O2/g of soln) / 100)] x (1.0 g soln/mL soln) x ( 1 mol H2O2/ 34.01 g H2O2) × (1000 mL/1L) So the g of H2O2 cancels, and the mass of solution cancels, so the units left are mol of H2O2 per mL soln which is the definition of Molarity.
(Experiment 3): 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. Select one or more: 1. CuSO4 2. CuO 3. Cu 4. Cu(OH)2
3. Cu
(Experiment 6): What solution color will be observed at the end point in the buret ? Select one: 1. Colorless 2. Pink 3. Dark blue
3. Dark blue
Will under-titrating the end point in Part III affect the value of mg of Vitamin C? Select one: 1. No effect 2. Raises the value of mg of Vitamin C 3. Lowers the value of mg of Vitamin C
3. Lowers the value of mg of Vitamin C
(Experiment 5): Which chemical(s) will be in the buret? Select one or more: 1. H2O 2. Fruit juice 3. NaOH 4. (C6H5OH)2C2O2C6H4 (phenolphthalein)
3. NaOH
Identify the reaction type for the generic reaction given. A + B → A+n + B-m Select one: 1. Decomposition 2. Single Displacement 3. Oxidation-Reduction 4. Double Displacement 5. Combination
3. Oxidation-Reduction
(Experiment 5): 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: Used a dirty spatula and got some NiCl2·6 H2O in with the product during weighing Select one: 1. Lowers the actual yield 2. No effect 3. Raises the actual yield
3. Raises 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: Not pulling air through the crystals (to dry crystals) Select one: 1. No effect 2. Lowers the actual yield 3. Raises the actual yield
3. Raises the actual yield
An 7.50 mL aliquot of a 125 ppm stock Red 40 dye solution was diluted to a final volume of 25.0 mL with deionized water. What is the concentration of the dilute Red 40 dye solution (in ppm)? Select one: 37.5 ppm 41.7 ppm 1.50 ppm 23.4 ppm
37.5 ppm
What should you so if you spill NaOH on the lab bench? Select one: 1. Leave the spill on the bench and let it evaporate. 2. Add H2SO4 to the spill to neutralize it and notify the TA. 3. Wash the lab bench for 15 minutes with solution from the eye wash station and notify the TA. 4. Clean the spill using a chemical absorbent pad from the chemical spill kit.
4. Clean the spill using a chemical absorbent pad from the chemical spill kit.
Which definition corresponds to theoretical yield? Select one: 1. The reactant that is completely consumed during the reaction. 2. A small portion of a chemical species. 3. A chemical species that contains a metal ion that is coordinated to ligands. 4. The amount of product that could be produced using a given amount of reactant. 5. The reactant that is present as extra material when the reaction is complete.
4. The amount of product that could be produced using a given amount of reactant.
What will result when water (density = 1.0 g/mL), liquid M (density = 0.65 g/mL, immiscible with H2O), and liquid N (density = 0.80 g/mL, immiscible with M and H2O) are poured into test tube. Select one: 1. Three layers will form in the test tube. Water is the top layer, liquid N is middle layer, and liquid M is the bottom layer. 2. Two layers will form in the test tube. Water is the top layer, a mixture of liquid N and liquid M is the bottom layer. 3. Three layers will form in the test tube. Water is the bottom layer, liquid M is middle layer, and liquid N is the top layer. 4. Three layers will form in the test tube. Water is the bottom layer, liquid N is middle layer, and liquid M is the top layer. 5. Two layers will form in the test tube. Water is the bottom layer, a mixture of liquid N and liquid M is the top layer.
4. Three layers will form in the test tube. Water is the bottom layer, liquid N is middle layer, and liquid M is the top layer.
When is it okay to remove your chemical splash proof goggles? 1. When the goggles fog up 2. When washing glassware 3. When not working with acids or bases 4. When everyone in the lab has put away all chemicals and glassware.
4. When everyone in the lab has put away all chemicals and glassware.
Which definition corresponds to aliquot? Select one: 1. A chemical species that contains a metal ion that is coordinated to ligands. 2. The amount of product that could be produced using a given amount of reactant. 3. The reactant that is completely consumed during the reaction. 4. The reactant that is present as extra material when the reaction is complete. 5. A small portion of a chemical species.
5. A small portion of a chemical species.
Identify the reaction type for the generic reaction given. A + B → AB Select one: 1. Oxidation-Reduction 2. Decomposition 3. Double Displacement 4. Single Displacement 5. Combination
5. Combination
(Experiment 5): What color is expected for the product, [Ni(C2H8N2)3]Cl2, if C2H8N2 is the limiting reagent? Select one: 1. Dark Purple 2. Dark Blue 3. Blue-green 4. Lime green 5. Pink-violet
5. Pink-violet
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 Select one: A. 9.79 g B. 9.90 g C. 11.9 g D. 10.04 g
A. 9.79 g
(Experiment 4): Which statement best explains what happens to the percent yield if the crystals (product) were washed with hot water? Select one: A. The actual yield will decrease since part of the product will dissolve and not be recovered as a solid. Since actual yield is in the numerator, the percent yield will also decrease. B. The actual yield will increase since the original amount of product will now absorb water. Since the actual yield is in the numerator, the percent yield will also increase. C. The actual yield will increase since the original amount of product will now absorb water. And since the actual yield is in the denominator, the percent yield will decrease. D. The actual yield will decline since part of the product will dissolve and not be recovered as a solid. But since the actual yield is in the denominator, the percent yield will increase.
A. The actual yield will decrease since part of the product will dissolve and not be recovered as a solid. Since actual yield is in the numerator, the percent yield will also decrease.
(Experiment 3): What is the mole to mole ratio between Cu(C2H3O2)2·H2O and NaC7H4SO3N·H2O? Select one: A. 2 mol Cu(C2H3O2)2·H2O : 1 mol NaC7H4SO3N·H2O B. 1 mol Cu(C2H3O2)2·H2O : 2 mol NaC7H4SO3N·H2O C. 2 mol Cu(C2H3O2)2·H2O : 3 mol NaC7H4SO3N·H2O D. 1 mol Cu(C2H3O2)2·H2O : 1 mol NaC7H4SO3N·H2
B. 1 mol Cu(C2H3O2)2·H2O : 2 mol NaC7H4SO3N·H2O
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 Select one: Nonelectrolyte Strong electrolyte Weak electrolyte
Strong electrolyte
Cedrick & Astrid titrated a 10.00 mL aliquot of grapefruit juice with a 0.171 M NaOH solution to the end point. They calculated that there was 0.1698 g of citric acid present in the juice sample. What is the amount mg of citric acid present per mL of juice? Select one: A. 10.1 mg/mL B. 7.06 mg/mL C. 1.70 mg/mL D. 17.0 mg/mL
D. 17.0 mg/mL
Zach and Nate calculated the theoretical yield as 6.57 g of Cu(C7H4SO3N)2(H2O)4·2 H2O. They recovered 4.53 g of Cu(C7H4SO3N)2(H2O)4·2 H2O. What is the percent yield? Select one: A. 98.0 % B. 31.1% C. 75.6 % D. 68.9% E. 45.1%
D. 68.9%
What is the density of a liquid that occupies a volume of 3.29 mL and weighs 2.98 g? Select one: 1. 0.31 g/mL 2. 0.91 g/mL 3. 1.10 g/mL 4. 1.30 g/mL
D=m/v --> 2. 0.91
In the reaction below, classify the chemical species as the type of electrolyte. Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + 2 H2O(ℓ) H2SO4 Select one: Strong electrolyte Nonelectrolyte Weak electrolyte
Strong electrolyte
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 Askor & Bich found that it required 14.81 mL of 1.07 x 10-3 M DCIP solution to reach the endpoint when titrating a 6.00 mL aliquot of pear juice. 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) ?
How many mg of ascorbic acid, C6H8O6, are present in the juice aliquot ? 2.79 How many mL of this juice would Bich have to drink in order to meet the Daily Recommended Intake (DRI) ? 194
A common error in titration is over-titrating. Which of the following statement(s) is/are TRUE for the citric acid titration? 1. Over-titrating means too much analyte was added to the reaction. 2. Since the volume of titrant is too large, multiplying by a large number in the calculation of citric acid makes the mass of citric acid too high. 3. Over-titrating in this reaction produces a dark pink (or peach) solution. Select one: I and II are TRUE. I and III are TRUE. II and III are TRUE. Only I is TRUE.
II and III are TRUE.
Piers & Aida performed this experiment together. However, when Piers did his calculations he forgot to subtract the vapor pressure of O2(g) while Aida did do this part of the calculations. Which of the following statement(s) are TRUE concerning Piers' calculations? I. Piers' calculations will still yield the same molarity of H2O2 as Aida. II. Piers' calculations will give a higher value of moles of H2O2(g) than Aida. III. Piers' calculations will give a higher partial pressure of O2(g) than Aida Select one: Only I is true. I & II are true. II and III are true. I and III are true.
II and III are true.
(Experiment 8): 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? Select one: liter atmosphere Kelvin grams
Kelvin
Which of the following statements are TRUE if the titration of fruit juice (Part III) was over-titrated? Too much DCIP was added in the titration, causing the Molarity of the ascorbic acid to be lowered. The amount of Vitamin C will be higher since the larger volume of DCIP is in the numerator in the Vitamin C calculation. The amount of Vitamin C would be lower since overtitrating makes the Molarity of DCIP lower and the Molarity of DCIP is in the numerator of the Vitamin C calculation. Select one: Only I and III are TRUE. Only I and II are TRUE. Only II and III are TRUE. Only II is TRUE.
Only II is TRUE.
Ethyl, Ann & Ami reacted 2.00 g of NiCl2·6 H2O with 7.00 mL of 4.00 M C2H8N2. They recovered 1.68 g of product, (Ni(C2H8N2)3)Cl2. The theoretical yield of the product is ___________. The percent yield of the product is ____________.
The theoretical yield of the product is 2.61 g The percent yield of the product is 64.4% To find the theoretical yield: If NiCl2· 6H2O is Limiting Reagent: 1. Calculate moles of NiCl2· 6 H2O using mass of NiCl2· 6 H2O and dividing by its molar mass 2. Use that number and the mole:mole ratio to find moles of product 3. Calculate mass of product (theoretical yield) using previous number & Molar mass of the product. If ethylenediamine (C2H8N2) solution is Limiting Reagent: 1. Calculate moles of C2H8N2 using Molarity x Liters of C2H8N2: 2. Use that number and the mole:mole ratio to find moles of product 3.Calculate mass of product (theoretical yield) using previous number & Molar mass of the product. Then compare the mass of product by each reagent, whichever is the SMALLER VALUE, is the theoretical yield To find % yield: Divide the actual or experimental yield by the theoretical yield (smaller number), and multiply by 100%
(Experiment 7): What is the conductivity classification for an unknown E that dissolves completely in water and only has a few of ions present in solution? Select one: Strong electrolyte Weak electrolyte Nonelectrolyte
Weak electrolyte
(Experiment 7): What is the conductivity classification for an unknown A that dissolves completely in water and partially dissociates into ions? Select one: Weak electrolyte Nonelectrolyte Strong electrolyte
Weak electrolyte
(Experiment 7): What is the conductivity classification for an unknown H that only partially ionizes in water? Select one: Weak electrolyte Strong electrolyte Nonelectrolyte
Weak electrolyte
Predict the conductivity of H3BO3, a weak acid. Select one: Strong electrolyte Nonelectrolyte Weak electrolyte
Weak electrolyte
Predict the conductivity of NH2CH2CH2NH2, a weak base. Select one: Nonelectrolyte Strong electrolyte Weak electrolyte
Weak electrolyte
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? __________ of NaOH What is the mass of citric acid in the juice sample? _________ of H3C6H5O7
What is the volume of NaOH titrated? ____19.51______ of NaOH What is the mass of citric acid in the juice sample? _____0.146____ of H3C6H5O7 To calculate the Volume of NaOH titrated into the flask is: Final Buret volume - Initial Buret Volume = volume titrated To find mass of Citric acid in the juice, you need to: 1. Calculate the moles of NaOH M NaOH x Vol. NaOH titrated = moles NaOH reacted 2. Calculate the moles of Citric Acid (H3C6H5O7) mole NaOH reacted x [1 mol H3C6H5O7 / 3 mol NaOH] = mol of H3C6H5O7 3. Calculate the mass of H3C6H5O7 mol of H3C6H5O7 x Molar Mass of H3C6H5O7 = mass of H3C6H5O7
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 increase of Ba+2 and OH- ions. III. At the equivalent point, the conductivity is nearly zero since all the Ba+2 and OH- ions have reacted to produce nonelectrolyte products. IV. After the endpoint, the conductivity increases due to the excess titrant. Select one or more: a. III and IV are TRUE. b. I & III are TRUE. c. II & III are TRUE. d. I & II are TRUE.
a. III and IV are TRUE.
What should you do if some NaOH comes into contact with your skin? Select one: a. Dry the skin with a chemical absorbent pad from the chemical spill kit. b. Wash your eyes for 15 minutes with water from the eyewash and notify the TA. c. Wash the skin for 15 minutes with water and notify the TA. d. Put a bandage (from the first aid kit) on the skin and notify the TA.
c. Wash the skin for 15 minutes with water and notify the TA.
1Which definition corresponds to a titrant? Select one: a. A chemical species that has a pH value < 7.0. b. A chemical species that changes colors at different pH values. c. The chemical species of interest. d. The chemical species being added in a titration.
d. The chemical species being added in a titration.
The ability of a solid or gas to dissolve in a liquid is its _______________.
solubility
The substance being dissolved is the ________________.
solute
The solution that does the dissolving is the _______________.
solvent