quiz 5

Quiz 5

Due: 11:50pm on Monday, October 29, 2012

Note: You will receive no credit for late submissions. To learn more, read your instructor's Grading Policy

Question 1

Part A

Complete and balance the following molecular equation.

Express your answer as a balanced chemical equation. Identify all of the phases in your answer.

ANSWER:

Correct

Part B

Write the net ionic equation for it.

Express your answer as a balanced net ionic equation. Identify all of the phases in your answer.

ANSWER:

Correct

Part C



ANSWER:

Correct

Part D



ANSWER:

Correct

Part E



ANSWER:

Correct

Part F



ANSWER:

Correct

Question 2

Designate the Bronsted-Lowry acid and the Bronsted-Lowry base on the left side of each equation, and alsodesignate the conjugate acid and conjugate base on the right side.

Part A

ANSWER:

Correct

Part B

ANSWER:

is the B-L acid; is the B-L base. is the conj. acid; is the

conj. base.


conj. base.


conj. base.


conj. base.

is the B-L acid; is the B-L base. is the conj. acid; is

the conj. base.


the conj. base.


the conj. base.


the conj. base.

Correct

Part C

ANSWER:

Correct

Question 3

Complete the following table by calculating the missing entries. In each case indicate whether the solution is acidicor basic.

Acidic or basic?

7.5!10"3

3.5!10"10

8.25

5.73

Part A

Complete the first row.

Express your answer using two significant figures.


conj. base.


conj. base.


conj. base.


conj. base.

ANSWER:

Correct

Part B


Express your answer using two decimal places.

ANSWER:

Correct

Part C



ANSWER:

Correct

Part D

Complete the first row. Indicate whether the solution is acidic or basic.

ANSWER:

= 1.3!10"12

= 2.12

= 11.88

acidic

basic

Correct

Part E

Complete the second row.


ANSWER:

Correct

Part F



ANSWER:

Correct

Part G



ANSWER:

Correct

Part H

= 2.9!10"5

= 4.54

= 9.46

Complete the second row. Indicate whether the solution is acidic or basic.

ANSWER:

Correct

Part I

Complete the third row.


ANSWER:

Correct

Part J



ANSWER:

Correct

Part K



ANSWER:

acidic

basic

= 5.6!10"9

= 1.8!10"6

= 5.75

Correct

Part L

Complete the third row. Indicate whether the solution is acidic or basic.

ANSWER:

Correct

Part M

Complete the fourth row.


ANSWER:

Correct

Part N



ANSWER:

Correct

acidic

basic

= 5.4!10"9

= 1.9!10"6

Part O



ANSWER:

Correct

Part P

Complete the fourth row. Indicate whether the solution is acidic or basic.

ANSWER:

Correct

Question 4

Calculate the of each of the following strong acid solutions.

Part A

8.5!10"3 ,


ANSWER:

Correct

= 8.27

acidic

basic

= 2.07

Part B

1.34 of in 560 of solution,

Express your answer using three decimal places.

ANSWER:

Correct

Part C

6.90 of 0.250 diluted to 54.0 ,


ANSWER:

Correct

Part D

A solution formed by mixing 15.0 of 0.130 with 17.0 of 0.200 .


ANSWER:

Correct

Question 5

Part A

= 1.421

= 1.496

= 0.777

Calculate for 1.4!10"3 .


ANSWER:

All attempts used; correct answer displayed

Part B

Calculate for 1.4!10"3 .


ANSWER:

Correct

Part C

Calculate for 2.460 of in 300.0 of solution.

Express your answer using four significant figures.

ANSWER:

Answer Requested

Part D

Calculate for 2.460 of in 300.0 of solution.

Express your answer using four decimal places.

ANSWER:

= 2.8!10"3

= 11.45

= 0.3424

Answer Requested

Part E

Calculate for 1.30 of 0.250 diluted to 1.50 .

Express your answer using three significant figures.

ANSWER:

Answer Requested

Part F

Calculate for 1.30 of 0.250 diluted to 1.50 .


ANSWER:

Correct

Part G

Calculate for a solution formed by adding 4.00 of 0.180 to 10.0 of 8.8!10"2

.


ANSWER:

= 13.5345

= 2.17!10"4

= 10.336

= 0.18

Correct

Part H

Calculate for a solution formed by adding 4.00 of 0.180 to 10.0 of 8.8!10"2 .


ANSWER:

Correct

Question 6

Write the chemical equation and the expression for the acid dissociation of each of the following acids in

aqueous solution. First show the reaction with as a product and then with the hydronium ion.

Part A

. Show the reaction with as a product.

Express your answer as a chemical equation. Identify all of the phases in your answer.

ANSWER:

Answer Requested

Part B

Write the expression for the acid dissociation from the previous part.

ANSWER:

= 13.25

Correct

Part C

. Show the reaction with the hydronium ion as a product.


ANSWER:

Answer Requested

Part D


ANSWER:

Correct

Part E

. Show the reaction with as a product.


ANSWER:

Correct

Part F


ANSWER:

Correct

Part G

. Show the reaction with the hydronium ion as a product.


ANSWER:

Correct

Part H


ANSWER:

Correct

Question 7

Calculate the of each of the following solutions ( and values are given in Appendix D in the textbook).

Part A

9.8!10"2 propionic acid .


ANSWER:

Correct

= 2.95

Part B

0.100 hydrogen chromate ion .


ANSWER:

Correct

Part C

0.119 pyridine .


ANSWER:

Correct

Question 8

Write the chemical equation and the expression for the reaction of each of the following bases with water.

Part A

Write the chemical equation for the reaction of propylamine, with water.

ANSWER:

Correct

= 3.76

= 9.15

Part B

Write the expression for the reaction of propylamine, with water.

ANSWER:

Correct

Part C

Write the chemical equation for the reaction of monohydrogen phosphate ion, with water.

ANSWER:

Answer Requested

Part D

Write the expression for the reaction of phosphate ion, with water.

ANSWER:

Correct

Part E

Write the chemical equation for the reaction of benzoate ion, with water.

ANSWER:

Correct

Part F

Write the expression for the reaction of benzoate ion, with water.

ANSWER:

Correct

Question 9

Part A

Calculate the molar concentration of ions in a 0.540 solution of hypobromite ion

.


ANSWER:

Correct

Part B

What is the of this solution?


ANSWER:

Correct

Question 10

The strength of an acid, , is often determined by the strength and polarity of the bond. In general, a

weaker and more polar bond leads to a stronger acid.

For binary acids of elements in the same group of the periodic table, the bond strength decreases down the

group, so acidity increases.For binary acids of elements in the same row of the periodic table, the polarity of the bond increases from left

= 1.5!10"3

= 11.17

to right (as the electronegativity of increases), so acid strength increases.

For oxoacids, acid strength increases with the oxidation number of the central atom. If the oxidation number is thesame, acid strength increases with the electronegativity of the central atom.

Part A

Rank the following compounds in order of decreasing acid strength using periodic trends.

Rank the acids from strongest to weakest. To rank items as equivalent, overlap them.

Hint 1. How to approach the problem

Locate the elements in the periodic table. Notice that and are in the same group, and are

in the same period, and and are in the same group. How does acid strength change within a

period and in a group?

Hint 2. Describe how the acidity changes in a group of the periodic table

Complete the following statement about the trend observed for binary acids of elements in the samegroup of the periodic table.

ANSWER:

CorrectThe strength of the bond decreases with increasing size of element down a group. The

weaker the bond, the easier it is to break it. Therefore the acidity increases.

Hint 3. Describe how the acidity changes in a period of the periodic table

Complete the following statement about the trend observed for binary acids of elements in the same rowof the periodic table.

ANSWER:

Acid strength

decreases

increases

stays the same as you move down a group.

Acid strength

decreases

increases

stays the same from left to right across a period.

CorrectIn a periodic row, the polarity of the bond increases with the increase in electronegativity of

element (from left to right). The more polar the bond, the easier it is to remove the proton.

Therefore, the acidity increases with the bond polarity.

ANSWER:

All attempts used; correct answer displayed

Part B

Without consulting the table of acid-dissociation constants, match the following acids to the given values.

Drag the appropriate items to their respective bins.


An acid-dissociation constant is a measure of the acid strength. The greater the value, the stronger

the acid. Therefore, we need to rank the acids according to their strength.

The strength of acid increases as the polarity of the bond increases. All three acids have the

same central atom, sulfur. The polarity of the proton bond increases with the increase in the oxidationnumber of the central atom. We can compare the oxidation numbers of in these compounds and rank

the acids.

Hint 2. Calculate the oxidation number of sulfur in

What is the oxidation number of sulfur in ?

ANSWER:



ANSWER:



ANSWER:

+2

+1

0

-1

-2

-2

-1

0

+1

+2

+3

+4

+5

+6

+7

ANSWER:

CorrectNotice that oxidation number and acid strength both increase with the number of oxygen atoms.

-2

-1

0

+1

+2

+3

+4

+5

+6

+7

Question 11

Part A

Calculate the of a buffer that is 0.115 in and 0.195 in .


ANSWER:

Correct

Part B

Calculate the of a solution formed by mixing 65 of 0.33 with 75 of 0.27 .


ANSWER:

Correct

Question 12

Part A

How many milliliters of 0.120 are needed to completely neutralize 49.0 of 0.108

solution?

ANSWER:

Correct

= 10.48

= 10.23

= 88.2

Part B

How many milliliters of 0.129 are needed to neutralize 0.160 of ?

ANSWER:

Correct

Part C

If 55.2 of solution is needed to precipitate all the sulfate ion in a 746 sample of , what is

the molarity of the solution?

ANSWER:

Correct

Part D

If 42.6 of 0.214 solution is needed to neutralize a solution of , how many grams of

must be in the solution?

ANSWER:

Correct

Question 13

Tartaric acid, , has two acidic hydrogens. The acid is often present in wines and precipitates from

solution as the wine ages. A solution containing an unknown concentration of the acid is titrated with . It

requires 25.65 of 0.1500 solution to titrate both acidic protons in 50.00 of the tartaric acid

solution.

= 15.5

= 9.51!10"2

= 0.338

Part A

Write a balanced net ionic equation for the neutralization reaction.

ANSWER:

Answer Requested

Part B

Calculate the molarity of the tartaric acid solution.

Express your answer using four significant figures.

ANSWER:

Correct

Question 14

A sample of 0.2140 of an unknown monoprotic acid was dissolved in 25.0 of water and titrated with

. The acid required 27.4 of base to reach the equivalence point.

Part A

What is the molar mass of the acid?

ANSWER:

Correct

Question 15

3.848!10"2

= 82.2

By the Brnsted-Lowry definition, acids are proton donors and bases are proton acceptors. By the Lewis definition,acids are electron-pair acceptors, and bases are electron-pair donors. For bases, the two definitions are equivalentsuch that all Lewis bases are Brnsted-Lowry bases and vice versa.However, it is possible to have a Lewis acid that is not a Brnsted-Lowry acid. This is because Lewis acids includemolecules and cations that have a vacant valence orbital, regardless of whether they have a proton to donate.Common examples of Lewis acids (that are not Brnsted-Lowry acids) are metal ions, such as and . The

following is an example of a Lewis acid-base reaction:

donates the electron pair to . Therefore, is a Lewis base, and is a Lewis acid.

Part A

Identify the Lewis acid in the following reaction:


The chromium(III) cation has empty 4s and 3d subshells. The water molecule, , has two loneelectron pairs. To identify the Lewis acid, determine which molecule or ion accepts an electron pair.

ANSWER:

CorrectEach of six anions donates a pair of electrons to , which has six vacant valence orbitals.

Part B

Classify each of the following as a Lewis acid or a Lewis base.

Drag the appropriate items to their respective bins.


Lewis acids have vacant valence orbitals and can accept an unshared electron pair from a Lewis base.Common examples of Lewis acids are cations of metals, such as and . Examples of neutral

Lewis acids are halides of group 3A elements, such as . Additional examples of Lewis acids are

oxides of nonmetals, such as and . An anion cannot be a Lewis acid because it already has a

negative charge and won't accept more electrons.

ANSWER:

Correct

Part C

In the following pair, which species would you expect to be the stronger Lewis acid?


A Lewis acid accepts a lone pair of electrons from a Lewis base. Because opposite charges attract, the

greater the positive charge on the cation, the greater its ability to attract negatively charged electrons.

ANSWER:

Correct

Score Summary:

Your score on this assignment is 84.8%.You received 12.72 out of a possible total of 15 points.

quiz 5

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