ChemLab 1212 Midterm

C

What is the density of a liquid that occupies a volume of 5.14 mL and weighs 5.89 g?

A. 0.75 g/mL
B. 0.873 g/mL
C. 1.15 g/mL
D. 1.74 g/mL

C

When ethanol(ℓ) is added to water, it results in one solution. What describes the relationship between ethanol and water?

A. Soluble
B. Insoluble
C. Miscible
D. Immiscible

C
A and B

Liquid C is immiscible with Liquids A & B. Liquid B is miscible with Liquid A. The liquids were poured into the beaker in order of increasing density. Select the appropriate label for each layer.

Liquid C: 28.1 g, 20.0 mL
Liquid A: 21.8 g, 20.0 mL
Liquid B: 9.2 g, 10.0 mL

Which chemical species is in the bottom layer?
Which chemical species is the top layer?
A. Liquid A
B. Liquid B
C. Liquid C

B

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.

A. 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.

B.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.

C. 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.

D. 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.

E. 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.

B

An experimental method to estimate the density of a crystal is to compare it to a variety of solution of known densities. Solution M (density = 0.65 g/mL), Solution N (density = 0.80 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 S is insoluble in each. When a few crystals of S are added to the test tube, it sinks through all the solutions. What is the best approximate density of S?

A. Density of S is less than 0.65 g/mL.
B. Density of S is greater than 1.0 g/mL. Correct
C. Density of S is greater than 0.80 g/mL but less than 1.0 g/mL.
D. Density of S is greater than 0.65 g/mL but less than 0.80 g/mL.

Single Displacement

Identify the reaction type for the generic reaction given.
AC + B → A + BC

Combination

Identify the reaction type for the generic reaction given.
A + B → AB

Decomposition

Identify the reaction type for the generic reaction given.
ABC → AB + C

Oxidation-Reduction

Identify the reaction type for the generic reaction given.
A + B → A+n + B-m

Double Displacement

Identify the reaction type for the generic reaction given.
AB + XY → AY + BX

2
Combination
2
1

From the description of the reaction below, balance the equation and also select the classification of the reaction.

When silver Mg(s) is ignited in the presence of O2(g), it forms a white, powdery solid, MgO(s).

___ Mg(s) + ___ O2(g) → ___ MgO(s)

Coefficient in front of Mg(s)?
Classification of reaction?
Coefficient in front of MgO(s)?
Coefficient in front of O2(g)?

B

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.

A. Cu(OH)2
B. CuSO4
C. Cu
D. CuO

B

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.

A. Cu
B. Cu(OH)2
C. CuO
D. CuSO4

A

In this reaction, you observed several different Cu species which had different physical attributes.

Select the appropriate chemical formula(s) that corresponds to a brown solid.

A. Cu
B. Cu(OH)2
C. CuO
D. CuSO4

C

What is the mole to mole ratio between Cu(C2H3O2)2·H2O and NaC7H4SO3N·H2O?

A. 2 mol Cu(C2H3O2)2·H2O : 1 mol NaC7H4SO3N·H2O
B. 1 mol Cu(C2H3O2)2·H2O : 1 mol NaC7H4SO3N·H2O
C. 1 mol Cu(C2H3O2)2·H2O : 2 mol NaC7H4SO3N·H2O
D. 2 mol Cu(C2H3O2)2·H2O : 3 mol NaC7H4SO3N·H2O

6.88
9.28
74.1

Cooper and Zach did this experiment dissolving 3.46 g of Cu(C2H3O2)2·H2O and adding 7.74 g NaC7H4SO3N·H2O.

They recovered 6.88 g of product.
In their calculations, they found that 9.28 g of product should be produced.
Their calculation of (6.88 g/9.28 g) x 100% is equal to 74.1%.

What is the actual yield?
What is the theoretical yield?
What is the percent yield?

A

Cooper, Zach and Nate did this experiment dissolving 3.50 g of Cu(C2H3O2)2·H2O and adding 7.90 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

A. 9.39 g
B. 9.48 g
C. 11.4 g
D. 9.63 g

C

Zach and Nate calculated the theoretical yield as 6.30 g of Cu(C7H4SO3N)2(H2O)4·2 H2O. They recovered 4.49 g of Cu(C7H4SO3N)2(H2O)4·2 H2O.
What is the percent yield?

A. 98.2 %
B. 40.4%
C. 71.2%
D. 28.8%
E. 73.6 %

6.04 g
85.8 g

In a similar experiment, Cooper, Zach & Nate started with 2.25 g of Cu(C2H3O2)2·H2O and 5.13 g of NaC7H4SO3N·H2O and obtained 5.18 g of Cu(C7H4SO3N)2(H2O)4·2H2O.

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

The theoretical yield of the product is ________.
The percent yield of the product is ________.

C

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:

Weighing the crystals while the crystals are still wet

A. No effect
B. Lowers the actual yield
C. Raises the actual yield

B

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 sodium saccharinate while transferring the solid to the beaker

A. No effect
B. Lowers the actual yield
C. Raises the actual yield

C

Which statement best explains what happens to the percent yield if the crystals (product) were washed with hot water?

A. 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.

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 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.

D. 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.

A

Which definition corresponds to excess reagent?

A. The reactant that is present as extra material when the reaction is complete.

B. A chemical species that contains a metal ion that is coordinated to ligands.

C. A small portion of a chemical species.

D. The amount of product that could be produced using a given amount of reactant.

E. The reactant that is completely consumed during the reaction.

C

Which definition corresponds to coordination compound?

A. The reactant that is present as extra material when the reaction is complete.

B. The reactant that is completely consumed during the reaction.

C. A chemical species that contains a metal ion that is coordinated to ligands.

D. A small portion of a chemical species.

E. The amount of product that could be produced using a given amount of reactant.

B

Which definition corresponds to limiting reagent?

A. A small portion of a chemical species.

B. The reactant that is completely consumed during the reaction.

C. The reactant that is present as extra material when the reaction is complete.

D. The amount of product that could be produced using a given amount of reactant.

E. A chemical species that contains a metal ion that is coordinated to ligands.

2.75 g
Limiting reagent
Chemical present in excess
3.51 g

Nick and Kel reacted 3.10 g of NiCl2· 6 H2O with 8.50 mL of 4.00 M C2H8N2. They recovered 2.75 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

The actual or experimental yield is ____.

The chemical, C2H8N2, is the _____.

The chemical, NiCl2· 6 H2O, is the _____.

The theoretical yield is ______.

E

What color is expected for the product, [Ni(C2H8N2)3]Cl2, if NiCl2·6 H2O is the limiting reagent?

A. Blue-green
B. White
C. Dark Blue
D. Lime green
E. Pink-violet
F. Dark Purple

C

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:
Rinsing the crystals with water

A. No effect
B. Raises the actual yield
C. Lowers the actual yield

Z

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

A. No effect
B. Raises the actual yield
C. Lowers the actual yield

3.49 g
70.7%

Ethyl, Ann & Ami reacted 3.33 g of NiCl2·6 H2O with 8.45 mL of 4.00 M C2H8N2. They recovered 2.47 g of product, (Ni(C2H8N2)3)Cl2.

The theoretical yield of the product is ______.

The percent yield of the product is _____.

C

Which definition corresponds to an acid-base indicator?

A. The chemical species being added in a titration.
B. A chemical species that has a pH value < 7.0.
C. A chemical species that changes colors at different pH values.
D. The chemical species of interest.

A
D

Which chemical(s) will be in the Erlenmeyer flask (before titration begins)?

Select one or more:
A. (C6H5OH)2C2O2C6H4 (phenolphthalein)
B. NaOH
C. H2O
D. Fruit juice

15.51 mL
0.170 g

Cedrick & Astrid titrated a 10.00 mL aliquot of grapefruit juice with a 0.171 M NaOH solution to the end point.
The initial buret reading was 1.31 mL and the final buret reading was 16.82 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?

A

Cedrick & Astrid titrated a 15.00 mL aliquot of grapefruit juice with a 0.134 M NaOH solution to the end point. The initial buret reading was 1.04 mL and the final buret reading was 24.83 mL. They calculated that there was 0.2042 g of citric acid present in the juice sample. What is the amount mg of citric acid present per mL of juice?

A. 13.6 mg/mL
B. 40.8 mg/mL
C. 8.22 mg/mL
D. 3.06 mg/mL
E. 5.41 mg/mL

B
C

Molar Mass of Citric acid (H3C6H5O7) = 192.12 g/mol
H3C6H5O7(aq) + 3 NaOH(aq) → Na3C6H5O7(aq) + 3 H2O(l)

Vida & Mindy titrated a 15.0 mL aliquot of grapefruit juice to its endpoint and it used 18.23 mL of a 0.0998 M NaOH solution.

How many grams of citric acid are present in their aliquot?
What is the milligrams of citric acid per mL of juice?

A. 0.0959 g
B. 0.1165 g
C. 7.77 mg/mL
D. 0.3495 g
E. 19.17 mg/mL
F. 6.39 mg/mL

B

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 adding the phenolphthalein to the flask and stopping when the buret is empty

A. No effect
B. Raises the value of mg citric acid/mL juice
C. Lowers the value of mg citric acid/mL juice

C

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?

Using the Molarity of NaOH used in the practice problem (0.1065 M) instead of the Molarity of NaOH recorded on the bottle (0.121 M) in the calculations

A. No effect
B. Raises the value of mg citric acid/mL juice
C. Lowers the value of mg citric acid/mL juice

C

What color is the 2,6-dichloroindophenol solution initially?

A. Colorless
B. Pink
C. Dark blue

G
A
E

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. 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 DCP to reach the endpoint. What is the Molarity of the DCP solution?

A 15.00 mL aliquot of pear juice required 15.47 mL of the same DCP solution (from above) to reach the end point.
How many mg of C6H8O6 are present in the aliquot?

A. 2.10 x 10-3 M
B. 1.06 x 10-2 M
C. 1.03mg
D. 15.9 mg
E. 5.71 mg
F. 1.87 x 10-1 M
G. 6.03 x 10-3 M
H. 6.95 x 10-4 M

A

Will use of a lower Molarity value of ascorbic acid affect the calculated Molarity of DCIP?

A. Lowers the value of Molarity of DCIP
B. No effect
C. Raises the value of Molarity of DCIP

C

Will use of a higher Molarity value of DCIP affect the calculated mg of Vitamin C?

A. Lowers the value of mg of Vitamin C
B. No effect
C. Raises the value of mg of Vitamin C

B

Which of the following statements are TRUE if the titration of fruit juice (Part III) was over-titrated?

I. Too much DCIP was added in the titration, causing the Molarity of the ascorbic acid to be lowered.
II. The amount of Vitamin C will be higher since the larger volume of DCIP is in the numerator in the Vitamin C calculation.
III. 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:
A. Only I and III are TRUE.
B. Only II is TRUE.
C. Only I and II are TRUE.
D. Only II and III are TRUE.

2.62
430

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 12.81 mL of 1.16 x 10-3 M DCIP solution to reach the endpoint when titrating a 12.50 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)?

C

What is the conductivity classification for an unknown G that ionizes completely in water?

Select one:
A. Weak electrolyte
B. Non-electrolyte
C. Strong electrolyte

B

What is the conductivity classification for an unknown C that dissolves completely in water and but doesn't dissociate into ions?

Select one:
A. Strong electrolyte
B. Non-electrolyte
C. Weak electrolyte

B

What is the conductivity classification for an unknown A that dissolves completely in water and partially dissociates into ions?

Select one:
A. Strong electrolyte
B. Weak electrolyte
C. Non-electrolyte

A

Predict the conductivity of CH3CH2OH, a molecular compound.

Select one:
A. Non-electrolyte
B. Weak electrolyte
C. Strong electrolyte

A

Predict the conductivity of NH2(CH3), a weak base.

Select one:
A. Weak electrolyte
B. Strong electrolyte
C. Non-electrolyte

C

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

Select one:
A. Weak electrolyte
B. Non-electrolyte
C. Strong electrolyte

C

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:
A. Non-electrolyte
B. Weak electrolyte
C. Strong electrolyte

B

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.

Select one or more:
A. III and IV are TRUE.
B. II & IV are TRUE.
C. I & III are TRUE.
D. I & II are TRUE.

0.221M

What is the Molarity of the Ba(OH)2 solution if a 6.00 mL aliquot of the Ba(OH)2 solution required 13.90 mL of a 0.0955 M H2SO4 solution to reach the equivalence point?

Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + 2 H2O(l)

A

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 volume of O2(g)?

Select one:
A. milliliters
B. torr
C. Kelvin
D. grams

D

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:
A. grams
B. atmosphere
C. liter
D. Kelvin

A

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?

Select one:
A. torr
B. grams
C. milliliters
D. Kelvin

o.9458 atm O2
0.002894 mol O2
0.005788 mol H2O2
0.926 M H2O2

Consider an experiment where 6.25 mL of an unknown H2O2(aq) solution reacted with the yeast at 25.2°C to produce 75.16 mL of gas. The barometric pressure was 740.3 torr. The vapor pressure of H2O is 23.8 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?

C

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:
A. Only I is true.
B. I & II are true.
C. II and III are true.
D. I and III are true.

3.53 M

Ozzie wanted to do another experiment using 12.0% (by mass) H2O2.

What is the Molarity of this H2O2 solution?

198

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.

A

A 0.0578 g sample of sodium salicylate was dissolved and diluted to a final volume of 250 mL with deionized water. What is the concentration of the sodium salicylate solution?

Select one:
A. 1.444 x 10-3 M
B. 2.312 x 10-4 M
C. 2.701 x 10-3 M
D. 1.108 x 10-2 M

A

An 7.50 mL aliquot of 2.75 x 10-3 M sodium salicylate was diluted to a final volume of 125 mL with FeCl3 solution. What is the concentration of the dilute sodium salicylate solution?

Select one:
A. 1.65 x 10-4 M
B. 4.58 x 10-5 M
C. 2.58 x 10-5 M
D. 3.41 x 10-4 M

A

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 1750 M-1. The absorbance of a dilute aspirin solution mixed with FeCl3 was 0.88.

What is the concentration of the dilute aspirin solution?

Select one:
A. 5.03 x 10-4 M
B. 1.54 x 10-2 M
C. 1.99 x 10-3 M
D. 6.49 x 10-4 M