Quiz 5 105q42

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 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 D 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 E 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 F 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

Question 2 Designate the Bronsted-Lowry acid and the Bronsted-Lowry base on the left side of each equation, and also designate the conjugate acid and conjugate base on the right side.

Part A

ANSWER: is the B-L acid;

is the B-L base.

is the conj. acid;

is the

is the B-L base.

is the conj. acid;

is the

is the B-L base.

is the conj. acid;

is the

is the B-L base.

is the conj. acid;

is the

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

Correct

Part B

ANSWER: is the B-L acid;

is the B-L base.

is the conj. acid;

is

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

is the B-L base.

is the conj. acid;

is

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

is the B-L base.

is the conj. acid;

is

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

is the B-L base.

is the conj. acid;

is

Correct

Part C

ANSWER: is the B-L acid;

is the B-L base.

is the conj. acid;

is the

is the B-L acid;

is the B-L base.

is the conj. acid;

is the

is the B-L acid;

is the B-L base.

is the conj. acid;

is the

is the B-L acid;

is the B-L base.

is the conj. acid;

is the

conj. base.

conj. base.

conj. base.

conj. base.

Correct

Question 3 Complete the following table by calculating the missing entries. In each case indicate whether the solution is acidic or 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.

ANSWER: = 1.3!10"12

Correct

Part B Complete the first row. Express your answer using two decimal places. ANSWER: = 2.12

Correct

Part C Complete the first row. Express your answer using two decimal places. ANSWER: = 11.88

Correct

Part D Complete the first row. Indicate whether the solution is acidic or basic. ANSWER: acidic basic

Correct

Part E Complete the second row. Express your answer using two significant figures. ANSWER: = 2.9!10"5

Correct

Part F Complete the second row. Express your answer using two decimal places. ANSWER: = 4.54

Correct

Part G Complete the second row. Express your answer using two decimal places. ANSWER: = 9.46

Correct

Part H

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

Correct

Part I Complete the third row. Express your answer using two significant figures. ANSWER: = 5.6!10"9

Correct

Part J Complete the third row. Express your answer using two significant figures. ANSWER: = 1.8!10"6

Correct

Part K Complete the third row. Express your answer using two decimal places. ANSWER: = 5.75

Correct

Part L Complete the third row. Indicate whether the solution is acidic or basic. ANSWER: acidic basic

Correct

Part M Complete the fourth row. Express your answer using two significant figures. ANSWER: = 5.4!10"9

Correct

Part N Complete the fourth row. Express your answer using two significant figures. ANSWER: = 1.9!10"6

Correct

Part O Complete the fourth row. Express your answer using two decimal places. ANSWER: = 8.27

Correct

Part P Complete the fourth row. Indicate whether the solution is acidic or basic. ANSWER: acidic basic

Correct

Question 4 Calculate the

of each of the following strong acid solutions.

Part A 8.5!10"3

,

Express your answer using two decimal places. ANSWER: = 2.07

Correct

Part B 1.34 of

in 560

of solution,

Express your answer using three decimal places. ANSWER: = 1.421

Correct

Part C 6.90

of 0.250

diluted to 54.0

,

Express your answer using three decimal places. ANSWER: = 1.496

Correct

Part D A solution formed by mixing 15.0

of 0.130

Express your answer using three decimal places. ANSWER: = 0.777

Correct

Question 5 Part A

with 17.0

of 0.200

.

for 1.4!10"3

Calculate

.

Express your answer using two significant figures. ANSWER: = 2.8!10"3

All attempts used; correct answer displayed

Part B for 1.4!10"3

Calculate

.

Express your answer using two decimal places. ANSWER: = 11.45

Correct

Part C Calculate

for 2.460 of

in 300.0

of solution.

Express your answer using four significant figures. ANSWER: = 0.3424

Answer Requested

Part D Calculate

for 2.460 of

in 300.0

of solution.

Express your answer using four decimal places. ANSWER:

= 13.5345

Answer Requested

Part E Calculate

for 1.30

of 0.250

diluted to 1.50

.

Express your answer using three significant figures. ANSWER: = 2.17!10"4

Answer Requested

Part F Calculate

for 1.30

of 0.250

diluted to 1.50

.

Express your answer using three decimal places. ANSWER: = 10.336

Correct

Part G Calculate

for a solution formed by adding 4.00

. Express your answer using two significant figures. ANSWER: = 0.18

of 0.180

to 10.0

of 8.8!10"2

Correct

Part H Calculate

for a solution formed by adding 4.00

of 0.180

to 10.0

of 8.8!10"2

Express your answer using two decimal places. ANSWER: = 13.25

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 ANSWER:

expression for the acid dissociation from the previous part.

.

Correct

Part C . Show the reaction with the hydronium ion as a product. Express your answer as a chemical equation. Identify all of the phases in your answer. ANSWER:

Answer Requested

Part D Write the ANSWER:

expression for the acid dissociation from the previous part.

Correct

Part E . Show the reaction with

as a product.

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

Correct

Part F Write the

expression for the acid dissociation from the previous part.

ANSWER:

Correct

Part G . Show the reaction with the hydronium ion as a product. Express your answer as a chemical equation. Identify all of the phases in your answer. ANSWER:

Correct

Part H Write the

expression for the acid dissociation from the previous part.

ANSWER:

Correct

Question 7 Calculate the

of each of the following solutions (

Part A 9.8!10"2

propionic acid

.

Express your answer using two decimal places. ANSWER: = 2.95

Correct

and

values are given in Appendix D in the textbook).

Part B 0.100

hydrogen chromate ion

.

Express your answer using two decimal places. ANSWER: = 3.76

Correct

Part C 0.119

pyridine

.

Express your answer using two decimal places. ANSWER: = 9.15

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, ANSWER:

Correct

with water.

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, ANSWER:

Answer Requested

Part D Write the ANSWER:

expression for the reaction of phosphate ion,

with water.

with water.

Correct

Part E Write the chemical equation for the reaction of benzoate ion,

with water.

ANSWER:

Correct

Part F Write the ANSWER:

expression for the reaction of benzoate ion,

with water.

Correct

Question 9 Part A Calculate the molar concentration of

ions in a 0.540

solution of hypobromite ion

. Express your answer using two significant figures. ANSWER: = 1.5!10"3

Correct

Part B What is the

of this solution?

Express your answer using two decimal places. ANSWER: = 11.17

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

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 the same, 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 in the same period, and

and

and

are in the same group,

and

are

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 same group of the periodic table. ANSWER: decreases Acid strength

increases

as you move down a group.

stays the same

Correct The 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 row of the periodic table. ANSWER: decreases Acid strength

increases stays the same

from left to right across a period.

Correct In a periodic row, the polarity of the element

bond increases with the increase in electronegativity of

(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 Drag the appropriate items to their respective bins.

values.

Hint 1. How to approach the problem 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 oxidation number 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: +2 +1 0 -1 -2

Hint 3. Calculate the oxidation number of sulfur in What is the oxidation number of sulfur in

?

ANSWER: -2 -1 0 +1 +2 +3 +4 +5 +6 +7

Hint 4. Calculate the oxidation number of sulfur in What is the oxidation number of sulfur in ANSWER:

?

-2 -1 0 +1 +2 +3 +4 +5 +6 +7

ANSWER:

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

Question 11 Part A Calculate the

of a buffer that is 0.115

in

and 0.195

in

.

Express your answer using two decimal places. ANSWER: = 10.48

Correct

Part B Calculate the

of a solution formed by mixing 65

of 0.33

with 75

of 0.27

Express your answer using two decimal places. ANSWER: = 10.23

Correct

Question 12 Part A How many milliliters of 0.120 solution? ANSWER: = 88.2

Correct

are needed to completely neutralize 49.0

of 0.108

.

Part B How many milliliters of 0.129

are needed to neutralize 0.160 of

?

ANSWER: = 15.5

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: = 9.51!10"2

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: = 0.338

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 requires 25.65 solution.

of 0.1500

solution to titrate both acidic protons in 50.00

of the tartaric acid

. It

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: 3.848!10"2

Correct

Question 14 A sample of 0.2140

of an unknown monoprotic acid was dissolved in 25.0

. The acid required 27.4

Part A What is the molar mass of the acid? ANSWER: = 82.2

Correct

Question 15

of water and titrated with

of base to reach the equivalence point.

By the Brønsted-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 equivalent such that all Lewis bases are Brønsted-Lowry bases and vice versa. However, it is possible to have a Lewis acid that is not a Brønsted-Lowry acid. This is because Lewis acids include molecules 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 Brønsted-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:

Hint 1. How to approach the problem The chromium(III) cation has empty 4s and 3d subshells. The water molecule, , has two lone electron pairs. To identify the Lewis acid, determine which molecule or ion accepts an electron pair.

ANSWER:

Correct Each of six

anions donates a pair of electrons to

Part B Classify each of the following as a Lewis acid or a Lewis base. Drag the appropriate items to their respective bins.

, which has six vacant valence orbitals.

Hint 1. How to approach the problem 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 oxides of nonmetals, such as

and

. Additional examples of Lewis acids are

. 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?

Hint 1. How to approach the problem 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.