CHEM125 – CHAPTER 04 – BASIC HOMEWORK II

CHAPTER 4 BASIC HOMEWORK II

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Question 1

Correctly match the element with the property. (Score = right – wrong)

Help: Element groups and properties

Metal that reacts with cold water to produce OH- and H2(g)Choose…HeNaCrSAu chem126-4b - Fluff Butt ReviewsVery inert metalChoose…HeNaCrSAu chem126-4b - Fluff Butt ReviewsMetal that does not react with water, but reacts with acid to produce H2 gasChoose…HeNaCrSAu chem126-4b - Fluff Butt ReviewsNon-metal that is not a noble gasChoose…HeNaCrSAu chem126-4b - Fluff Butt ReviewsNoble gas–inert, stable electron configurationChoose…HeNaCrSAu chem126-4b - Fluff Butt Reviews

Explanation

Nonmetals don’t conduct electricity; most like to form negative ions. All metals conduct electricity. (The valence electrons which can move throughout the metal conduct the electricity.) In reactions, metals like to lose electrons and form positive ions. The alkali metals are the most reactive group of metals. They are so reactive that they react with cold water to produce the hydroxide ion and hydrogen gas. The alkaline earth metals are the next most reactive group. Most of them also react with cold water to produce the hydroxide ion and hydrogen gas. For example, 2Li(s) + 2H2O(l) –> 2Li+(aq) + 2OH-(aq) +H2(g) Many metals are reactive enough to react with acid to produce hydrogen, such as Al, Cr, and Fe. For example, 2Fe(s) + 6H+(aq) –> 2Fe3+(aq) + 3H2(g) A few metals are so inert that they won’t react with acid or even oxygen, such as Ag, Au, and Pt.

Question 2

Which compound is the most ionic?

Help: Ionic compounds and electronegativity

Select one: chem126-4b - Fluff Butt Reviews

Explanation

Metals and nonmetals combine to make ionic compounds. The metal exists as a positive ion and the nonmetal as a negative ion.

The ionic compounds are held together by strong electrostatic forces between the negative and positive ions and exist in the solid state. Because of these strong attractive forces, ionic compounds in the solid state do not conduct electricity.

In the liquid or molten state, the ions are free to move. The movement of ions causes them to conduct electricity.

Many ionic compounds dissolve in water and the process of dissolution separates the ions, making them free to move and conduct electricity.

Compounds aren’t 100% ionic. The greater the difference in electronegativity the more ionic the compound. Electronegativity is a measure of how much an element wants an additional electron or electrons. The more to the right and the more to the top in the periodic table the greater the electronegativity. F is the most electronegative. The more to the left and down in the periodic table the smaller the electronegativity. Cs has the smallest electronegativity of the non-radioactive elements. PT Ionic

Question 3

Which of the following compounds are ionic? (All must be correct to get credit.)

Help: Polyatomic ions and ionic compounds

Select one or more: chem126-4b - Fluff Butt Reviews chem126-4b - Fluff Butt Reviews chem126-4b - Fluff Butt Reviews

Explanation

Ionic compounds also consist of a positive metal ion and a polyatomic negative ion. For example, the phosphate ion (PO43-) is a polyatomic ion and FePO4 is an ionic compound.

Question 4

Which of the following ionic compounds are soluble (dissolve) in water?

Help: Solubility rules

Select one or more: chem126-4b - Fluff Butt Reviews chem126-4b - Fluff Butt Reviews chem126-4b - Fluff Butt Reviews

Explanation

Question 5

Which of the following compounds are soluble? Select one or more: chem126-4b - Fluff Butt Reviews chem126-4b - Fluff Butt Reviews chem126-4b - Fluff Butt Reviews

Question 6

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) Help: Strength of electrolytes

Explanation

Fully dissolves in water

Question 7

CaCl2(s) (strong, weak, or non electrolyte)

Explanation

Fully dissolves in water

Question 8

PbCl2(s) (strong, weak, or non electrolyte)

Explanation

PbCl2(s) is an insoluble compound–it does not dissolve.

Question 9

O2(g) (strong, weak, or non electrolyte) Oxygen hint

Explanation

Does not dissolve in water

Question 10

HCl(g) (strong, weak, or non electrolyte) HCl hint

Explanation

Fully dissolves in water

Question 11

Acetic acid (CH3COOH) (strong, weak, or non electrolyte)

Explanation

Partially dissolves in water

Question 12

What conducts electricity in metals? (One word answer)

Question 13

What conducts electricity in solutions? (One word answer)

Question 14

Which of the following statements about ionic compounds are true?Select one or more: chem126-4b - Fluff Butt Reviews chem126-4b - Fluff Butt Reviews chem126-4b - Fluff Butt Reviews

Question 15

What is the molarity of 0.46 mol of NaCl in enough water to make 4.0 L of solution? Help: Molarity example chem126-4b - Fluff Butt Reviews

Explanation

molarity=mol/L= 0.46 mol NaCl/4.0L = 0.115 M

Question 16

What is the molarity of the Al3+ ions when 0.25 mol of aluminum nitrate, Al(NO3)3, is dissolved in enough water to make 3.0 L of solution?chem126-4b - Fluff Butt Reviews

Explanation

0.25 mol/ 3 L = 0.0833 M 1 mol of Al3+ in Al(NO3)3 —> 0.0833 Al3+ M

Question 17

What is the molarity of the nitrate ions when 0.61 mol of barium nitrate, Ba(NO3)2, is dissolved in enough water to make 5.0 L of solution?chem126-4b - Fluff Butt Reviews

Explanation

0.61 mol Ba(NO3)2/ 5 L = 0.122 molarity 2 mols of NO3 in each mol Ba(NO3)2 0.122 M (2) = 0.244 M

Question 18

Calculate the molarity of calcium hydroxide that has been prepared by dissolving 1.47 g of calcium hydroxide in water and diluting the solution to a final volume of 3.00 L. Molarity calculation example chem126-4b - Fluff Butt Reviews

Explanation

1.47 g Ca(OH)2/ (74.093 g/mol Ca(OH)2) = 0.01984 mol Ca(OH)2 0.01984 mol Ca(OH)2 / 3L = 0.00661331 M Ca(OH)2

Question 19

Calculate the molarity of the hydroxide ions in a solution that has been prepared by dissolving 15.3 g of barium hydroxide (Ba(OH)2) in water and diluting the solution to a final volume of 4.00 L. (M.W’s: Ba 137.3 g/mol., O 16.0 g/mol, and H 1.0 g/mol)chem126-4b - Fluff Butt Reviews

Explanation

Remember there are 2 moles of hydroxide for each mole of barium hydroxide. 15.3 g Ba(OH)2 / (171.3 g/mol Ba(OH)2) = 0.08931699 moles0.08931699(2)= 0.178863 moles OH- [2 moles of OH- in Ba(OH)2]0.17863 moles / 4 L = .04465 M OH-

Question 20

How many moles of H+ are in 443 mL of 0.33 M nitric acid, HNO3? Calculating moles chem126-4b - Fluff Butt Reviews

Explanation

443 mL = 0.443 L 0.33 mol HNO3/ L * 0.443 L = 0.14619 mol HNO3 0.14619 mol H+ (1:1 ration of H+:HNO3)

Question 21

How many moles of OH- are in 430 mL of 0.82 M NaOH? chem126-4b - Fluff Butt Reviews

Explanation

0.430 L * 0.82 mol NaOH/L = 0.3526 mol NaOH 0.3526 mol OH- (1:1 ration OH-: NaOH)

Question 22

How many moles of Cl- are in 369 mL of 0.10 M FeCl3?chem126-4b - Fluff Butt Reviews

Explanation

0.10 mol FeCl3 / 1L * 0.369 L = 0.0369 FeCl3 3(0.0369) = 0.1107 mol Cl- (3:1 ration Cl: FeCl3)

Question 23

Match correctly. Electrolyte and nonelectrolyte solubility Solubility rules (review) AgBrChoose…soluble; strong electrolyteinsoluble; nonelectrolytesoluble; strong electrolyte; includes polyatomic ionsoluble; nonelectrolyte chem126-4b - Fluff Butt ReviewsCaCl2Choose…soluble; strong electrolyteinsoluble; nonelectrolytesoluble; strong electrolyte; includes polyatomic ionsoluble; nonelectrolyte chem126-4b - Fluff Butt ReviewsCH3OHChoose…soluble; strong electrolyteinsoluble; nonelectrolytesoluble; strong electrolyte; includes polyatomic ionsoluble; nonelectrolyte chem126-4b - Fluff Butt Reviews(NH4)2SChoose…soluble; strong electrolyteinsoluble; nonelectrolytesoluble; strong electrolyte; includes polyatomic ionsoluble; nonelectrolyte chem126-4b - Fluff Butt Reviews

Explanation

Question 24

In the reaction, AgNO3(aq) + NaCl(aq)–> NaNO3(?) + AgCl(?), what is the precipitate? Precipitation reaction Select one: chem126-4b - Fluff Butt Reviews

Explanation

Insoluble product/compound = precipitate Hint: It obviously cannot be an ion because if it was an ion that would mean it had the viability to dissociate and is therefore soluble

Question 25

What are the spectator ions?Select one or more: chem126-4b - Fluff Butt Reviews chem126-4b - Fluff Butt Reviews

Explanation

Spectator ions are not involved in the precipitate or the main reaction and are typically part of a soluble compound in the product.

Question 26

What are the reactant ions in the net ionic equation?Select one or more: chem126-4b - Fluff Butt Reviews chem126-4b - Fluff Butt Reviews

Explanation

Spectator ions are not included in tenet ionic equation as they appear as themselves in both the products and reactants. While the other ions may appear as ions on one side but as a compound on the other.

Question 27

In the reaction of hydrochloric acid and lithium hydroxide, what liquid is formed? (Either write the name or the formula in the space provided.) Acid-base neutralization reaction

Explanation

HCl + Li(OH) –> H2O (l) + LiCl (aq) H+ + Cl- + Li+ + OH- –> H2O + Li+ + Cl-

Question 28

What is the positive spectator ion? (The nitrate ion would be written NO3-)

Question 29

What is the negative spectator ion?

Question 30

In the reaction between a solution of Al2(SO4)3 and Ca(OH)2, what is (are) the precipitates? Hint, consider reviewing the solubility rules in the supplement.Select one or more: chem126-4b - Fluff Butt Reviews chem126-4b - Fluff Butt Reviews

Explanation

Al2(SO4)3 + 3Ca(OH)2 —> 2Al (OH)3 + 3Ca(SO4) 2 precipitates are formed [Look back at the solubility rules for clarification]