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Quiz #1 (1/27/14)

Quiz #1 (1/27/14). One the board, you will see a sketch of the cell formed by Cd in Cd(NO 3 ) 2 and Cu in Cu(NO 3 ) 2 Which metal forms the anode of this cell? ANSWER – Cadmium (Cd) Write the cell notation for this cell. ANSWER – Cd | Cd 2+ || Cu 2+ | Cu

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Quiz #1 (1/27/14)

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  1. Quiz #1 (1/27/14) One the board, you will see a sketch of the cell formed by Cd in Cd(NO3)2 and Cu in Cu(NO3)2 • Which metal forms the anode of this cell? ANSWER – Cadmium (Cd) • Write the cell notation for this cell. ANSWER – Cd | Cd2+ || Cu2+ | Cu • Calculate the overall cell potential for this cell. ANSWER - 0.34 – (-0.40) = +0.74 V Reduction Potentials: Cd2+ + 2e- Cd = -0.40V Cu2+ + 2e-  Cu = 0.34V

  2. Quiz 2 (1/29/14) • True or false: At chemical equilibrium, the rate of the forward reaction equals the rate of the reverse reaction. ANSWER - True

  3. Quiz 2 (1/29/14 - continued) Questions 5 and 6 refer to the chemical reaction given here: CO(g) + 3H2 (g) CH4 (g) + H2O (g) • Write out the expression for the equilibrium constant (Keq) ANSWER: [CH4][H2O] [CO] [H2]3 6. If the value of Keq for this reaction is 5.5 x 10-4, you will have more REACTANTSpresent at equilibrium.

  4. Quiz 3 (1/31/14) • For the reaction: H2 + I2 2 HI (g), the concentrations at equilibrium are: [H2] = 0.11 M, [I2] = 0.11M, [HI] = 0.78M Calculate the value of Keq for this reaction to the nearest whole number. ANSWER: (.78)2 = 50 (.11) (.11)

  5. Quiz 3 (1/31/14 – continued) Given the same reaction: H2 + I2 2 HI • How does the system shift when hydrogen gas is added to the reaction? (To the left or to the right?) ANSWER: RIGHT • How does the system shift when hydrogen iodide is removed from the reaction? (To the left or to the right?) ANSWER: RIGHT

  6. Quiz 4 (2/3/14) Given the exothermic reaction: C2H4 (g) + Br2 (g) C2H4Br2 (g) How does the equilibrium shift (Left, Right, or None) when: • The temperature is increased - LEFT • The pressure is increased - RIGHT • A catalyst is added to the reaction - NONE

  7. Quiz 5 (2/5/14) • A Bronsted-Lowry acid is defined as a proton DONOR. • Since Sulfuric acid (H2SO4) has two acidic protons it is known as a(n) diprotic acid. • Can the chemical species HCO3-1 act as an acid, a base, or both?

  8. Quiz 6 (2/7/14) • Write the formula for the conjugate base of HSO4-1. Answer: SO4-2 The acid/base reaction below is used for questions 17 and 18. HF (g) + H2O (l)  F- (aq) + H3O+ (aq) What are the chemical formulas of the two acid species in the reaction above? Answer: HF and H3O+ 19. Is nitric acid (HNO3) a weak or a strong acid?

  9. Quiz 7 (2/10/14) For the reaction: HCN (g) + OH- (aq) ?? 20 and 21. Write the chemical formulas of the products of this reaction. ANSWER: HCN + OH - CN - + H2O • Which side (left or right) is favored at equilibrium? ANSWER – RIGHT (weaker acid and weaker base) • If a sample has a [H3O+] = 2.5 x 10-6 what is the value of the [OH-] ? ANS: 1x10-14 = (2.5x10-6)(OH-) so, (OH-) = 1x10-14 / 2.5x10-6 = 4x10-9M

  10. Quiz 8 (2/12/14) You are given a sample of 1.75M NaOH. STRONG BASE!! • What is the [OH-] of this sample? Answer: 1.75M • What is the [H3O+] of this sample? Answer: 1x10-14 / 1.75 = 5.71 x 10-15 M • What is the pH of this sample? Answer: -log 5.71x10-15 = 14.2

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