CHEM126 - CHAPTER 15 - BASIC HOMEWORK / INTRO ACIDS

CHAPTER 15 BASIC HOMEWORK:

INTRO. ACIDS

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Question 1

What conducts electricity in metals? (One word answer)

Select from: electrons, ions, neutrons, nucleus, positrons, and protons

Answer:

Explanation

BRO COME ON…negatively charged particle found in atoms

Question 2

What conducts electricity in solutions? (One word answer)

Answer:

Explanation

General word for both cations and anions…aka please don’t embarrass me you know this

Question 3

Which of the following statements about ionic compounds is FALSE?

Select one:

a. An ionic compound consists of postive and neqative ions held together by electrostatic attraction.
b. An ionic compound in the solid state conducts electricity. Correct

c. A molten ionic compound (liquid state) conducts electricity.
d. If an ionic compound dissolves in water, the resulting solution conducts electricity, that is, it is an electrolyte.

Explanation

Ill let this one slide if you didn’t know it, but come on can solid salt conduct electricity there answer is NO because the ions are not free to move around.

Question 4

Classify the following compounds as strong electrolyte, weak electrolyte, or non-electrolyte. Write strong, weak, or non, respectively in the space for the answer.

KCl(s)

Electrolytes defined

Qualitative electrolyte rules

Answer: Correct

Explanation

Does this completely dissociate?? YES IT DOES why because of the solubility rules that you should have memorized last semester

Question 5

CaCl₂(s)

Answer: Correct

Explanation

Question 6

PbCl₂(s)

Answer: Correct

Question 7

O₂(g)Answer: Correct

Question 8

HCl(g)Answer: Correct

Question 9

Acetic acid (CH₃COOH)

Answer: Correct

Question 10

What is the molarity of 0.77 mol of NaCl in enough water to make 5.0 L of solution?

Definition and examples of Molarity

Answer: Correct

Explanation

0.77 mol NaCl / 5 L = 0.154 [NaCl]

Question 11

What is the molarity of the Al³⁺ ions when 0.42 mol of aluminum nitrate, Al(NO₃)₃, is dissolved in enough water to make 4.0 L of solution?Answer: Correct

Explanation

Al(NO₃)₃ is a strong electrolyte. ( 1 Mol of Aluminum ions per mol)

0.42/ 4 * 1 = 0.105

Question 12

What is the molarity of the nitrate ions when 0.47 mol of barium nitrate, Ba(NO₃)₂, is dissolved in enough water to make 3.0 L of solution?Answer: Correct

Explanation

Ba(NO₃)₂ is a strong electrolyte.( 2 Mols of Nitrate ions per mol)

0.47/ 3 * 2 = 0.313

Question 13

Calculate the molarity of calcium hydroxide that has been prepared by dissolving 2.87 g of calcium hydroxide in water and diluting the solution to a final volume of 4.00 L.

Example molarity calculation

Answer: Correct

Explanation

2.87 g Ca(OH)2 / 74.069 g/mol = 0.0387 mol

0.0387 mol/ 4 L = 0.009696

Question 14

Calculate the molarity of the hydroxide ions in a solution that has been prepared by dissolving 27.5 g of barium hydroxide (Ba(OH)₂) in water and diluting the solution to a final volume of 5.00 L. (M.W’s: Ba 137.3 g/mol., O 16.0 g/mol, and H 1.0 g/mol)

Answer: Correct

Explanation

Remember there are 2 moles of hydroxide for each mole of barium hydroxide.

Question 15

What is the molarity of the H⁺ ions in 0.50 M HCl?

Examples of acids and bases

Select one:

a. 0 M
b. << 0.5 M (much less)
c. < 0.5 M
d. 0.5 M Correct

Explanation

STRONG ACID FULLY DISSOCIATES

Question 16

What is the molarity of the H⁺ ions in 0.50 M acetic acid, CH₃COOH?

Select one:

a. 0 M
b. << 0.5 M Correct

c. < 0.5 M
d. 0.5 M

Explanation

NOT STRONG ACID DOESNT FULLY DISSOCIATE

Question 17

What is the molarity of the H⁺ ions in 0.50 M hydrofluoric acid, HF?

Select one:

a. 0 M
b. << 0.5 M Correct

c. < 0.5 M
d. 0.5 M

Explanation

HF is a weak acid WHAT DOES THAT MEAN it will not fully dissociate aka very very little of it

Question 18

What is the molarity of the H⁺ ions in 0.40 M nitric acid, HNO₃?Select one:

a. 0 M
b. << 0.4 M
c. < 0.4 M
d. 0.4 M Correct

Explanation

STROMG ACIDS FULLY DISSOCIATE

Question 19

What is the molarity of the NO₃^– ions in 0.40 M nitric acid, HNO₃?

Select one:

a. 0 M
b. << 0.4 M
c. < 0.4 M
d. 0.4 M Correct

Explanation

0.40 *1 = 0.40

Explanation

NaOH is a strong base and will therefore fully disscoaite

Explanation

NH3 is a weak base, meaning that it will not fully dissociate and have very very little hydroxide ions

Question 22

What is the molarity of the OH^– ions in 0.040 M barium hydroxide, Ba(OH)₂?

Assume the barium hydroxide is fully dissociated into ions in the dilute solution.

Select one:

a. 0 M
b. << 0.04 M
c. < 0.04 M
d. 0.04 M
e. 0.08 M Correct

Explanation

0.040*2 = 0.08

Question 23

Match correct answers.

H⁺ is more accurately represented by adding a water molecule, that is, as H₃O⁺.

[H₃O⁺] = [OH^–]

Answer 1


[H₃O⁺] > [OH^–]	Answer 2


[H₃O⁺] < [OH^–]	Answer 3

Question 24

Check those statements which are true.

Concentration of acids and bases

Select one or more:

a. If [H₃O⁺] = 10^-4 M, then the solution is acidic. Correct

b. If [OH^–] = = 10^-9 M, then the solution is acidic. Correct

c. If [H₃O⁺] = 10^-7 M, then the solution is acidic.

d. If [H₃O⁺] = 10^-8 M, then the solution is acidic.

e. If [OH^–] = 10^-8 M, then the solution is acidic. Correct

Explanation

Use the equation -log[H+]=pH

as well as -log[H+] -log[OH-] = 14

Question 25

Calculate the hydroxide ion concentration, [OH^–], in 0.014 M HBr.

Acid/base calculation

Answer: Correct

Explanation

-log[0.014]+-log[OH-]=14

OH-= 7.14e-13

Question 26

Calculate the hydroxide ion concentration, [OH^–], in 1.95 M HNO₃.

Answer: Correct

Explanation

-log[1.95]+-log[OH-]=14

OH-= 5.128e-15

Question 27

Calculate the hydrogen ion concentration, [H⁺], in 0.00486 M NaOH.

Answer: Correct

Explanation

pH+pOH=14

-log[OH-]=pOH

-log[0.00486 M]=pOH

-log[H+] -log[0.00486 M]=14

H+=2.0576e-12

Question 28

Calculate the hydrogen ion concentration, [H⁺], in 0.00688 M Ba(OH)₂. Careful!

Answer: Correct

Explanation

pH+pOH=14

-log[OH-]=pOH

-log[2*0.00688]=pOH

-log[H+] -log[2*0.00688]=14

H+=7.267e-13

Question 29

The autodissociation of water to H⁺ and OH^– is endothermic. At a higher temperature more of the water molecules have sufficient energy to dissociate. So, K_w is greater.

At 25^oC, K_w = 1.0 x 10^-14. (standard K_w)
At 65^oC, K_w = 1.0 x 10^-13.

Calculate the hydrogen ion concentration, [H⁺], in 0.0636 M LiOH at 65^oC.

Answer: Correct

Explanation

Kw= 1e-13 = [0.0636][H+]

[H+]=1.57e-12

Question 30

What is the pH of a solution where the [H⁺] =8.28 x 10^-12 M?

REPORT pH TO 2 DECIMAL PLACES.

pH calculation

Answer: Correct

Explanation

pH=-log[8.28e-12]

pH=11.08

Question 31

Which of the following statements are true?

pH and acidity

Select one or more:

a. If the pH = 7, then the solution is neutral. Correct

b. If the pH = 5, then the solution is acidic. Correct

c. If the pH = 8, then the solution is acidic.
d. If the pH = 2, then the solution is basic.
e. If the pH = 1, then the solution is acidic. Correct

f. If the pH =12, then the solution is acidic.
g. If the pH = 9, then the solution is basic. Correct

Question 32

What is the pH of a solution where the [H⁺] =7.41 x 10^-12 M?

REPORT pH TO 2 DECIMAL PLACES.

Answer: Correct

Explanation

pH=-log[7.41e-12]

pH=11.13

Question 33

What is the pH of a solution where the [OH^–] =5.73 x 10^-1 M?

REPORT pH TO 2 DECIMAL PLACES.

Finding pH from [OH^–]

Answer: Correct

Explanation

pH+pOH=14

pH-log[5.73e-1]=14

pH=13.76

Question 34

What is the [H⁺] if the pH of a solution is 9.88?

Example for pH to [H⁺]

Answer: Correct

Explanation

9.88=-log[H+]

10^-9.88=10^log[H+]

1.318e-10=[H+]

Question 35

What is the [H⁺] if the pH of a solution is 2.44?

Answer: Correct

CHAPTER 15 BASIC HOMEWORK:

INTRO. ACIDS

Resources:

Question 1

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Question 2

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Question 3

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Question 4

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Question 5

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Question 6

Question 7

Question 8

Question 9

Question 10

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Question 11

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Question 12

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Question 13

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Question 14

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Question 15

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Question 16

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Question 17

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Question 18

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Question 19

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Question 20

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Question 21

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Question 22

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Question 23

Question 24

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Question 25

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Question 26

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Question 27

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Question 28

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Question 29

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Question 30

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Question 31

Question 32

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Question 33

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Question 34

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Question 35