WebAssign is not supported for this browser version. Some features or content might not work. System requirements

WebAssign

Welcome, demo@demo

(sign out)

Friday, March 28, 2025 22:01 EDT

Home My Assignments Grades Communication Calendar My eBooks

OpenStax - Chemistry: Atoms First 2/e (Homework)

James Finch

Chemistry - College, section 1, Fall 2019

Instructor: Dr. Friendly

Current Score : 38 / 42

Due : Friday, February 1, 2030 00:00 EST

Last Saved : n/a Saving...  ()

Print Assignment
Question
Points
1 2 3 4 5 6 7 8 9
2/2 4/4 1/2 2/2 24/24 0/2 1/2 1/1 3/3
Total
38/42 (90.5%)

  • Instructions

    Cengage is proud to support the open source teaching community through our partnership with OpenStax. OpenStax's Chemistry: Atoms First is now enriched with WebAssign homework questions and student learning resources and is available as a low-cost option. The WebAssign content includes immediate student feedback, question links to appropriate sections of the eBook, as well as complete unabridged access to the textbook from a dynamic table of contents.

    Questions 1-5 are end-of-chapter questions from the OpenStax Chemistry: Atoms First textbook. These questions contain full algorithmic solutions for all question parts and showcase the variety of randomizations that WebAssign performs (shown in red) as well as various modes for student responses. These questions are denoted with "E" in the Question Browser.

    Questions 6-9 are from the exclusive WebAssign General Chemistry collection. This collection contains almost 1,400 questions that are correlated to OpenStax's Chemistry and feature feedback, step-by-step tutorials with Deep Help, and detailed algorithmic solutions. These questions are denoted with "WA" in the Question Browser. This demo assignment allows many submissions and allows you to try another version of the same question for practice wherever the problem has randomized values.

    This demo assignment allows many submissions and allows you to try another version of the same question for practice wherever the problem has randomized values.

    The answer key and solutions will display after the first submission for demonstration purposes. Instructors can configure these to display after the due date or after a specified number of submissions.

Assignment Submission

For this assignment, you submit answers by question parts. The number of submissions remaining for each question part only changes if you submit or change the answer.

Assignment Scoring

Your last submission is used for your score.

1. 2/2 points  |  Previous Answers OSAtomsChem2 1.6.E.091. My Notes
Question Part
Points
Submissions Used
1 2
1/1 1/1
1/100 1/100
Total
2/2
 
Calculate these volumes.
(a)
What is the volume (in cm3) of 23 g lead,
density = 11.30 g/cm3?
WebAssign will check your answer for the correct number of significant figures. Correct: Your answer is correct. seenKey

2.0

 cm3
(b)
What is the volume (in L) of 3.44 g gaseous fluorine,
density = 1.553 g/L?
WebAssign will check your answer for the correct number of significant figures. Correct: Your answer is correct. seenKey

2.22

 L
†


Solution or Explanation
Process: Rearrange the known relationship for density to solve for the volume.
density = mass per unit of volume
volume = 
mass
density
(a)
What is the volume (in cm3) of 23 g lead,
density = 11.30 g/cm3?
23 g ✕ 
1 cm3
11.30 g
 = 2.035 cm3 ≅ 2.0 cm3
(b)
What is the volume (in L) of 3.44 g gaseous fluorine,
density = 1.553 g/L?
3.44 g ✕ 
1 L
1.553 g
 = 2.2151 L ≅ 2.22 L

Supporting Materials

Additional Materials

Your work in question(s) will also be submitted or saved.
Viewing Saved Work Revert to Last Response
2. 4/4 points  |  Previous Answers OSAtomsChem2 1.1.E.005. My Notes
Question Part
Points
Submissions Used
1 2 3 4
1/1 1/1 1/1 1/1
2/100 2/100 2/100 1/100
Total
4/4
 
Identify each of the bold items as a part of either the macroscopic domain, the microscopic domain, or the symbolic domain of chemistry. For those in the symbolic domain, indicate whether they are symbols for a macroscopic or a microscopic feature. (Select all that apply.)
(a)
A certain molecule contains two H atoms and one O atom.
Correct: Your answer is correct.

(b)
Zinc wire has a density of about 7 g/cm3.
Correct: Your answer is correct.

(c)
The bottle contains 13 grams of Ni powder.
Correct: Your answer is correct.

(d)
A phosphorus molecule is composed of 4 phosphorus atoms.
Correct: Your answer is correct.

†


Solution or Explanation
(a)
A certain molecule contains two H atoms and one O atom.
It is too small to be sensed directly: microscopic.
It uses specialized language: symbolic.
(b)
Zinc wire has a density of about 7 g/cm3.
It is large enough to be sensed directly: macroscopic.
(c)
The bottle contains 13 grams of Ni powder.
It is large enough to be sensed directly: macroscopic.
It uses specialized language: symbolic.
(d)
A phosphorus molecule is composed of 4 phosphorus atoms.
It is too small to be sensed directly: microscopic.

Supporting Materials

Additional Materials

Your work in question(s) will also be submitted or saved.
Viewing Saved Work Revert to Last Response
3. 1/2 points  |  Previous Answers OSAtomsChem2 11.2.E.011. My Notes
Question Part
Points
Submissions Used
1 2
1/1 0/1
2/100 3/100
Total
1/2
 
Consider the solutions presented.
(a)
Which of the following sketches best represents the ions in a solution of Al(BrO3)3(aq)?
     Correct: Your answer is correct.
(b)
Write a balanced chemical equation showing the products of the dissolution of Al(BrO3)3. (Include states-of-matter under the given conditions in your answer. Use the lowest possible whole number coefficients.)
Incorrect: Your answer is incorrect. seenKey

Al(BrO_3)_3(s) --> Al^3+(aq) + 3 BrO_3^-(aq)
Your answer contains an improperly or incompletely formatted chemical formula.
†


Solution or Explanation
(a)
Which of the following sketches best represents the ions in a solution of Al(BrO3)3(aq)?
The given formula represents a strong electrolyte with 3 polyatomic anions for each 1 cation per formula unit. Strong electrolytes dissolve completely in water, so beaker z is the only depiction that fits the given formula.
(b)
Write a balanced chemical equation showing the products of the dissolution of Al(BrO3)3.
Al(BrO3)3(s) → Al 3+(aq) + 3 BrO3−(aq)

Supporting Materials

Additional Materials

Your work in question(s) will also be submitted or saved.
Viewing Saved Work Revert to Last Response
4. 2/2 points  |  Previous Answers OSAtomsChem2 10.1.E.018. My Notes
Question Part
Points
Submissions Used
1 2
1/1 1/1
8/100 1/100
Total
2/2
 
Under certain conditions, molecules of formic acid, HCOOH, form "dimers," pairs of formic acid molecules held together by strong intermolecular attractions.
Draw a dimer of formic acid, showing how two HCOOH molecules are held together. (Use the "Any" bond type to indicate intermolecular attractions.)

Help

Marvin JS
Edit drawing
State the type of IMF that is responsible.
    
†

Supporting Materials

Additional Materials

Your work in question(s) will also be submitted or saved.
Viewing Saved Work Revert to Last Response
5. 24/24 points  |  Previous Answers OSAtomsChem2 13.4.E.061. My Notes
Question Part
Points
Submissions Used
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
1/1 1/1 1/1 1/1 1/1 1/1 1/1 1/1 1/1 1/1 1/1 1/1 1/1 1/1 1/1 1/1 1/1 1/1 1/1 1/1 1/1 1/1 1/1 1/1
1/100 1/100 1/100 2/100 1/100 1/100 1/100 1/100 1/100 1/100 1/100 1/100 1/100 1/100 2/100 2/100 2/100 2/100 2/100 1/100 1/100 2/100 1/100 2/100
Total
24/24
 
Please use the values in the resources listed below instead of the textbook values.
Complete the changes in concentrations (or pressure, if requested) for each of the following reactions.
(a)
Reaction 2 H2(g) + O2(g) equilibrium reaction arrow 2 H2O(g)
relative
change
−2x
Correct: Your answer is correct. -2x
−x
Correct: Your answer is correct. -x 		+2x
change in
concentration
(M) 		WebAssign will check your answer for the correct number of significant figures. Correct: Your answer is correct. seenKey

-1.50

 		WebAssign will check your answer for the correct number of significant figures. Correct: Your answer is correct. seenKey

-0.750

 		1.50
(b)
Reaction CS2(g) + 4 H2(g) equilibrium reaction arrow CH4(g) + 2 H2S(g)
relative
change 		+x
+4x
Correct: Your answer is correct. +4x
−x
Correct: Your answer is correct. -x
−2x
Correct: Your answer is correct. -2x
change in
concentration
(M) 		0.015 WebAssign will check your answer for the correct number of significant figures. Correct: Your answer is correct. seenKey

0.060

 		WebAssign will check your answer for the correct number of significant figures. Correct: Your answer is correct. seenKey

-0.015

 		WebAssign will check your answer for the correct number of significant figures. Correct: Your answer is correct. seenKey

-0.030
(c)
Reaction H2(g) + Cl2(g) equilibrium reaction arrow 2 HCl(g)
relative change +x
+x
Correct: Your answer is correct. +x
−2x
Correct: Your answer is correct. -2x
change in
pressure
(atm) 		1.40 WebAssign will check your answer for the correct number of significant figures. Correct: Your answer is correct. seenKey

1.40

 		WebAssign will check your answer for the correct number of significant figures. Correct: Your answer is correct. seenKey

-2.80
(d)
Reaction 2 NH3(g) + 2 O2(g) equilibrium reaction arrow N2O(g) + 3 H2O(g)
relative change
−23​x
Correct: Your answer is correct. -2x / 3
−23​x
Correct: Your answer is correct. -2x / 3
+13​x
Correct: Your answer is correct. +x / 3 		+x
change in
pressure
(torr) 		WebAssign will check your answer for the correct number of significant figures. Correct: Your answer is correct. seenKey

-40.8

 		WebAssign will check your answer for the correct number of significant figures. Correct: Your answer is correct. seenKey

-40.8

 		WebAssign will check your answer for the correct number of significant figures. Correct: Your answer is correct. seenKey

20.4

 		61.2
(e)
Reaction NH4HS(s) equilibrium reaction arrow NH3(g) + H2S(g)
relative change +x
+x
Correct: Your answer is correct. +x
change in
concentration
(M) 		9.4 ✕ 10−6 WebAssign will check your answer for the correct number of significant figures. Correct: Your answer is correct. seenKey

9.4e-06
(f)
Reaction Fe(s) + 5 CO(g) equilibrium reaction arrow Fe(CO)4(g)
relative change
−5x
Correct: Your answer is correct. -5x 		+x
change in
pressure
(atm) 		WebAssign will check your answer for the correct number of significant figures. Correct: Your answer is correct. seenKey

-0.080

 		0.016
†


Solution or Explanation
The relative change and change in concentration (or pressure) will have opposite signs on either side of the reaction. If the concentration/pressure of a reactant is increasing (positive relative change), any other reactants will also have a positive relative change, and the products will have a negative relative change. The opposite is true when the concentration/pressure of a product is increasing.
For each reaction, use the given relative change and the reaction coefficients to determine the other relative changes. Set the given change in concentration/pressure equal to the relative change to calculate the value of x. Substitute the value of x into the other relative changes to determine all changes in concentration/pressure.
(a)
Reaction 2 H2(g) + O2(g) equilibrium reaction arrow 2 H2O(g)
relative
change
−2x
−x
 		+2x
change in
concentration
(M) 		−1.50 −0.750 1.50
(b)
Reaction CS2(g) + 4 H2(g) equilibrium reaction arrow CH4(g) + 2 H2S(g)
relative
change 		+x
+4x
−x
−2x
change in
concentration
(M) 		0.015 0.060 −0.015 −0.030
(c)
Reaction H2(g) + Cl2(g) equilibrium reaction arrow 2 HCl(g)
relative change +x
+x
−2x
change in
pressure
(atm) 		1.40 1.40 −2.80
(d)
Reaction 2 NH3(g) + 2 O2(g) equilibrium reaction arrow N2O(g) + 3 H2O(g)
relative change
−2x
3
−2x
3
+x
3
 		+x
change in
pressure
(torr) 		−40.8 −40.8 20.4 61.2
(e)
Reaction NH4HS(s) equilibrium reaction arrow NH3(g) + H2S(g)
relative change +x
+x
change in
concentration
(M) 		9.4 ✕ 10−6 9.4 ✕ 10−6
(f)
Reaction Fe(s) + 5 CO(g) equilibrium reaction arrow Fe(CO)4(g)
relative change
−5x
 		+x
change in
pressure
(atm) 		−0.080 0.016

Supporting Materials

Additional Materials

Your work in question(s) will also be submitted or saved.
Viewing Saved Work Revert to Last Response
6. 0/2 points  |  Previous Answers OSAtomsChem2 6.1.WA.009. My Notes
Question Part
Points
Submissions Used
1 2
0/1 –/1
1/100 0/100
Total
0/2
 
(a) How many moles of CO2 contain 2.66 ✕ 1024 molecules?
WebAssign will check your answer for the correct number of significant figures. Incorrect: Your answer is incorrect. seenKey

4.42

 mol CO2

(b) What number of moles is equivalent to 6.71 ✕ 1021 atoms of Hg?
WebAssign will check your answer for the correct number of significant figures. mol Hg
Did you remember the number of particles contained in one mole of a substance? Did you recall how to set up and use a conversion factor?

Supporting Materials

Additional Materials

Your work in question(s) will also be submitted or saved.
Viewing Saved Work Revert to Last Response
7. 1/2 points  |  Previous Answers OSAtomsChem2 6.2.WA.013. My Notes
Question Part
Points
Submissions Used
1 2
1/1 0/1
1/100 1/100
Total
1/2
 
Write the molecular and empirical formulas for the compound with the following structural formula.

molecular formula:

chemPad

Help

C6H12
C6H12

empirical formula:

chemPad

Help

C6H12
CH2



Solution or Explanation

  • Step 1 of 4

    Write the given structural formula of the compound.

  • Step 2 of 4

    Count the number of atoms of each element shown in the structural formula.
    There are 6 C atoms and 12 H atoms.

  • Step 3 of 4

    Write the molecular formula by writing the symbols for each element with a subscript indicating the number of atoms of that element determined in Step 2. Assume subscripts of "1" are understood; do not write "1" subscripts in the molecular formula.
    The six atoms of C are indicated by a subscript "6". The twelve atoms of H are indicated by a subscript "12".

    The molecular formula of the compound is the following.
    C6H12

  • Step 4 of 4

    Determine the empirical formula of the compound from its molecular formula. Assume subscripts of "1" are understood; do not write "1" subscripts in the empirical formula.
    The ratio between C and H atoms is 6:12. The smallest equivalent whole-number ratio is 1:2. Therefore, the empirical formula of the compound is the following.
    CH2
Did you recall that the subscripts in molecular and empirical formulas indicate the ratios of the elements in a compound? Although empirical formulas can be determined directly from molecular formulas, the reverse is not true; molecular formulas cannot be determined from empirical formulas without additional information.

Supporting Materials

Additional Materials

Your work in question(s) will also be submitted or saved.
Viewing Saved Work Revert to Last Response
8. 1/1 points  |  Previous Answers OSAtomsChem2 6.2.WA.014. My Notes
Question Part
Points
Submissions Used
1
1/1
1/100
Total
1/1
 
A compound has an empirical formula of C2H3O and a molar mass of 172 g/mol. What is the molecular formula?

chemPad

Help

C8H12O4
C8H12O4



Solution or Explanation

  • Step 1 of 5

    Recall the definition of molar mass.
    molar mass = mass of one mole of a substance (in grams)
    The molar mass of a compound is found by summing the molar masses of its constituent atoms.
    molar mass of a compound in g/mol = formula mass of that compound in amu

  • Step 2 of 5

    Recall the definition of an empirical formula.
    An empirical formula expresses the simplest whole-number ratio of distinct atoms in a compound.

  • Step 3 of 5

    Calculate the molar mass of the given empirical formula C2H3O. (Enter unrounded values.)
    formula mass of C2H3O = (# C atoms)(atomic mass of C)
     + (# H atoms)(atomic mass of H)
     + (# O atoms)(atomic mass of O)
     = (2)(12.01 amu) + (3)(1.008 amu) + (1)(16.00amu)
     = 43.044 amu
    Therefore, the empirical molar mass of C2H3O is 43.044 g/mol.

  • Step 4 of 5

    Calculate the ratio between the given molar mass and the empirical molar mass calculated in Step 3.
    The ratio between the given molar mass of 172 g/mol and the calculated empirical molar mass of 43.044 g/mol is the following.
    172 g/mol
    43.044 g/mol
    		 = 3.996 (Enter an unrounded value. Use at least one more digit than given.)
    ≈4 (Rounded to the nearest whole number.)

  • Step 5 of 5

    Multiply the subscripts in the empirical formula by the calculated ratio from Step 4 to determine the molecular formula.
    C: 4 × 2 = 8
    H: 4 × 3 = 12
    O: 4 × 1 = 4
    Therefore, the actual molecular formula is:
    C8H12O4

Supporting Materials

Additional Materials

Your work in question(s) will also be submitted or saved.
Viewing Saved Work Revert to Last Response
9. 3/3 points  |  Previous Answers OSAtomsChem2 6.2.WA.019. My Notes
Question Part
Points
Submissions Used
1 2 3
1/1 1/1 1/1
1/100 2/100 3/100
Total
3/3
 
A 0.5850 g sample of an unknown acid was titrated with NaOH and found to contain 3.506 ✕ 10−3 mol acid. Another sample of the substance was subjected to elemental analysis, where it was determined that the composition of the unknown material is 57.18% C, 4.78% H, and 38.04% O.
(a) What is the molar mass of the unknown acid?
WebAssign will check your answer for the correct number of significant figures. Correct: Your answer is correct. seenKey

166.9

 g/mol

(b) What is the empirical formula of the unknown acid?

chemPad

Help

C2H2O
C2H2O

(c) What is the molecular formula of the unknown acid?

chemPad

Help

C8H8O4
C8H8O4


Solution or Explanation

  • Step 1 of 10

    (a) What is the molar mass of the unknown acid?

    Calculate the molar mass of the acid. Recall that the molar mass of a compound is
    grams X
    moles X
    ;
     therefore, the molar mass of the unknown acid is:
    molar mass = 
    (0.5850 g)
    (3.506 ✕ 10−3 mol)
     = 166.9 g/mol.
    The answer is shown with four significant figures to match the precision of the measured values.

  • Step 2 of 10

    (b) What is the empirical formula of the unknown acid?

    Assume that 100 g of the substance is available. Determine the mass, in grams, of each element in that quantity of substance. (Enter an unrounded value.)
    C: 57.18% of 100 g = 57.18 g C
    H: 4.78% of 100 g = 4.78 g H
    O: 38.04% of 100 g = 38.04 g O

  • Step 3 of 10

    Use the periodic table to determine the average molar mass of each element present in the substance. Recall that average atomic mass (in amu) is reported on the periodic table and is equivalent to molar mass (in g/mol).
    average molar mass of C: 12.01 g/mol
    average molar mass of H: 1.008 g/mol
    average molar mass of O: 16.00 g/mol

  • Step 4 of 10

    Calculate the number of moles of each element present in the substance. (Enter an unrounded value. Use at least one more digit than given.)
    C: 57.18 g C × 
    1 mol C
    12.01 g C
     = 4.761 mol C
    H: 4.78 g H × 
    1 mol H
    1.008 g H
     = 4.742 mol H
    O: 38.04 g O × 
    1 mol O
    16.00 g O
     = 2.3775 mol O

  • Step 5 of 10

    Divide the number of moles present in each element by the smallest number of moles represented by any of the elements. If the results are very close to positive integers, round them to the nearest integer. The smallest number of moles from Step 4 comes from oxygen (O), 2.3775 mol.
    C: 
    4.7610 mol
     
     
    2.3775 mol
     
     
    		 = 2.003 (rounded to 4 significant figures)
     = 2 (rounded to the nearest integer)
    H: 
    4.742 mol
     
     
    2.3775 mol
     
     
    		 = 1.99 (rounded to 3 significant figures)
     = 2 (rounded to the nearest integer)
    O: 
    2.3775 mol
     
     
    2.3775 mol
     
     
    		 = 1.000 (rounded to 4 significant figures)
     = 1 (rounded to the nearest integer)

  • Step 6 of 10

    Using the relative number of atoms in the formula determined in Step 5, write the empirical formula of the substance. The C, H, and O atoms in the substance exist in the ratio 2:2:1, respectively. The empirical formula is therefore the following.
    C2H2O

  • Step 7 of 10

    (c) What is the molecular formula of the unknown acid?

    Using the periodic table and empirical formula of the compound, calculate the molar mass of the empirical formula.
    Empirical formula mass of C2H2O = (2)(atomic mass of C) + (2)(atomic mass of H)
    + (1)(atomic mass of O)
     = (2)(12.01 amu) + (2)(1.008 amu) + (1)(16.00 amu)
     = 42.036 amu
    Formula mass in amu equals molar mass in g/mol, so the molar mass of the empirical formula is 42.036 g/mol.

  • Step 8 of 10

    Divide the empirical molecular mass of the substance by the empirical molecular mass of the fragment, and then round the quotient to the nearest integer.
    166.9 g/mol
    42.036 g/mol
    		 = 3.970 (rounded to 4 significant figures)
     = 4 (rounded to the nearest integer)

  • Step 9 of 10

    Multiply each subscript in the given original empirical formula, C2H2O, by the number calculated in Step 8 to obtain the molecular formula. C8H8O4

  • Step 10 of 10

    Summarize the answer. (a) The molar mass of the unknown acid is 166.9 g/mol.

    (b) The empirical formula of the unknown acid is the following.
    C2H2O

    (c) The molecular formula of the unknown acid is the following.
    C8H8O4

Supporting Materials

Additional Materials

Your work in question(s) will also be submitted or saved.
Viewing Saved Work Revert to Last Response
Home My Assignments
Enter a number with the correct number of significant figures.
Enter a number with the correct number of significant figures.
Answer is case sensitive.
Enter a number with the correct number of significant figures.
Enter a number with the correct number of significant figures.
Enter a number with the correct number of significant figures.
Enter a number with the correct number of significant figures.
Enter a number with the correct number of significant figures.
Enter a number with the correct number of significant figures.
Enter a number with the correct number of significant figures.
Enter a number with the correct number of significant figures.
Enter a number with the correct number of significant figures.
Enter a number with the correct number of significant figures.
Enter a number with the correct number of significant figures.
Enter a number with the correct number of significant figures.
Enter a number with the correct number of significant figures.
Enter a number with the correct number of significant figures.
Enter a number with the correct number of significant figures.