CHEM 1110 EXAM 3 REVIEW

26 Determine the oxidation number of S in the following sulfur-containing species: SOCl₂ Place your answer in the box. Express your answer using only an integer number proceeded by either a + sign (when the oxidation number is positive) or a - sign (when the oxidation number is negative). For example, for a species with oxidation number of "minus three", you should put -3 in the answer box. Note that there are no spaces within the expression.

+4

10 Indicate whether the following statement is true or false. In a combustion reaction, all the products are compounds. a) true b) false

False? Not necessarily ALL of the products are compounds? The word "all" was underlined on the exam. I took that as a hint.

Indicate whether the following statement is true or false. The oxidation number of any element in its elemental state is zero. a) true b) false

True?

7 Which of the following weak acids is the strongest? a) Ka = 1.75 x 10⁻⁵ b) Ka = 5.70 x 10⁻¹⁰ c) Ka = 6.28 x 10⁻⁵ d) Ka = 2.51 x 10⁻⁵ e) Ka = 1.1 x 10⁻⁷

c.) because it is the largest number of all the 10⁻⁵ figures. Just a guess really.

13 If the dissociation constant of a weak acid is 7.9 x 10⁻⁵, at what ratio should you adjust the concentration of the weak acid and its conjugate base in order to prepare a buffer that has a pH of 4.10? a) 0.0100 M weak acid with 0.100 M conjugate base b) 0.100 M weak acid with 0.0100 M conjugate base c) 0.100 M weak acid with 0.200 M conjugate base d) 0.200 M weak acid with 0.100 M conjugate base e) 0.200 M weak acid with 0.200 M conjugate base

e.) equal proportions because the pKa and pH are equal to one another, 4.10?

14 A 0.0800 M solution of a base, B, is 18.0% ionized. Calculate the value of the base ionization constant, Kb. a) 0.0144 b) 0.0656 c) 0.220 d) 0.00316 e) no correct response

0.00316

4 The Ka of a weak acid is 5.4 x 10⁻². What is the pKa of this acid? Place your answer in the box. Express your answer using only a number or numbers without text. Report your result in decimal notation and to the proper number of significant figures. All numbers are measured. 1.27

1.27

23 The Ka of hydrofluoric acid (HF) is 6.8 x 10⁻⁴. What is the pH of a buffer solution that is prepared from 0.0500 M HF and 0.00500 M sodium fluoride (NaF)? a) 3.2 b) 4.2 c) 2.2 d) 1.0

2.2 because the acid goes on bottom in the equation?

18 An aqueous solution has [OH-] = 8.5 x 10⁻⁵. What is the pH of this solution? Place your answer in the box. Express your answer using only a number or numbers without text. Report your result in decimal notation and to the proper number of significant figures. All numbers are measured. 9.93

Convert OH⁻ to H₃O⁺ and get pH from there.

2 Classify the following chemical reaction: 2 KClO₃ (s) <====> 2 KCl (s) + 3 O₂ (g) Choose all that apply. a) combustion reaction b) synthesis reaction c) decomposition reaction d) nonredox reaction e) redox reaction f) single-replacement reaction

Didn't feel confident. A 50% guess. Decomposition and...

5 Which of the following acids is a weak electrolyte? a) HNO₃ b) HCl c) HI d) HClO₄ e) H₂SO₃ f) HBr g) more than one correct response h) no correct response

HNO₃, HCl, HI, HClO₄, HBr are all Strong Acids. So is H₂SO₄, but H₂SO₃ is a weak acid, making it a weak electrolyte as well?

12 Consider the following given information about two reactions, each of which involves only two reactants: Reaction 1: high activation energy; high temperature; 2 mol/L concentration Reaction 2: high activation energy; low temperature; 1 mol/L concentration When the reactants for each reaction are first mixed, which reaction is faster? a) Reaction 1 b) Reaction 2

I don't even remember answering this one.

28 In an endothermic reaction, heat is a _________. a) reducing agent b) oxidizing agent c) product d) catalyst e) no correct response

It's a reactant, so I don't think it's quite considered to be a catalyst. Maybe?

15 Which of the following salts is classified as a "strong acid-strong base salt"? a) NH₄CN b) LiNO₃ c) Li₃PO₄ d) Na₂CO₃ e) NH₄Br

LiNO₃ because it is the love child (along with H₂O) of LiOH and HNO₃. LiOH + HNO₃ ----> LiNO₃ + H₂O LiOH = Strong Base HNO₃ = Strong Acid All other options were made with only one strong acid or base, but not both.

3 Write the equilibrium constant expression for the following reaction: 2 Na₂O (s) <====> 4 Na (l) + O₂ (g) a) Keq = [O₂] b) Keq = 1 ÷ [O₂] c) Keq = ([Na]₄[O₂]) ÷ [Na₂O]² d) Keq = [Na]² ÷ [NaO]² e) no correct response

Not confident. guessed b. I panicked.

9 Which of the following substances can be used to make a buffer with H₃PO₄? a) Na₃PO₄ b) NaHC₂O₄ c) NaH₂SO₄ d) NaH₂PO₄ e) Na₂HPO₄

a.) Na₃PO₄ Google Guess

11 For the reaction C₆H₆ (g) + 3 H₂ (g) <====> C₆H₁₂ (g) + heat Determine which of the following will shift the equilibrium to the left. a) adding a catalyst b) decreasing the temperature c) increasing the pressure by decreasing the volume of the container d) decreasing the concentration of H₂ e) increasing the concentration of C₆H₆

d.) decreasing the concentration of H₂ This question was one that I had on the quiz. Exact same wording and reaction.

8 What is the correctly balanced chemical equation for the neutralization reaction between HClO3 (perchlorous acid) and LiOH (lithium hydroxide)? a) 2 HClO₃ + LiOH <====> LiClO₃ + 2 H₂O b) HClO₃ + 2 LiOH <====> Li2ClO₃ + 2 H₂O c) HClO₃ + 2 LiOH <====> 2 LiClO₃ + H₂O d) HClO₃ + LiOH <====> LiClO₃ + H₂O e) 2 HClO₃ + 3 LiOH <====> 3 LiClO₃ + 2 H₂O f) no correct response

d.) was my half-baked guess. Because the equation is already balanced?