分析化學相關的幾題選擇題~

Question

1. Given:
acetic acid, pKa = 4.75
HSO4–, pKa = 1.92
HF, pKa = 3.45
The order of these acids from strongest to weakest is
A) HSO4– > acetic acid > HF
B) HF > acetic acid > HSO4–
C) acetic acid > HF > HSO4–
D) HSO4– > HF > acetic acid
E) HF > HSO4– > acetic acid

2. The pKa for HF is 3.45. This expression refers to which of the following reactions?
A) H3O+(aq) + OH–(aq) b 2H2O(l)
B) F–(aq) + H2O(l) b HF(aq) + OH–(aq)
C) F–(aq) + H3O+(aq) b HF(aq) + H2O(l)
D) HF(aq) + H2O(l) b F–(aq) + H3O+(aq)
E) HF(aq) + OH–(aq) b F–(aq) + H2O(l)

3. For the titration of 25.0 mL of 0.100 M HClO(aq) (pKa = 7.5) with 0.100 M NaOH(aq), the main species in solution after addition of 25.0 mL of base are
A) HClO(aq), ClO–(aq), and Na+(aq).
B) ClO–(aq) and Na+(aq).
C) HClO(aq), OH–(aq), and Na+(aq).
D) HClO(aq), H+(aq), and ClO–(aq).
E) ClO–(aq) and H+(aq).

4. The standard potential of the Ag+/Ag electrode is +0.80 V and the standard potential of the cell
Fe(s)|Fe3+(aq)mAg+(aq)|Ag(s) is +0.84 V. What is the standard potential of the Fe3+/Fe electrode?
A) +1.64 V
B) –1.64 V
C) –0.12 V
D) +0.04 V
E) –0.04 V

5. Consider the following reaction:
H2O(g) + C(s) b H2(g) + CO(g)
If the value of Kp for this reaction is 3.72 at 1000 K, and the equilibrium partial pressures of H2(g) and CO(g) are 1.50 atm, calculate the equilibrium partial pressure of H2O(g).
A) 0.403 atm
B) 1.65 atm
C) 2.48 atm
D) 1.50 atm
E) 0.605 atm

6. If a small amount of HCl(aq) is added to 0.10 M NH3(aq),
A) the equilibrium concentration of NH4+(aq) is increased.
B) Ka becomes larger.
C) no change occurs.
D) the equilibrium concentration of the ammonium ion is decreased.
E) the equilibrium concentration of ammonia increases.

7. Consider the reaction
3Fe(s) + 4H2O(g) b 4H2(g) + Fe3O4(s)
If the total pressure is increased suddenly by reducing the volume,
A) more H2(g) is produced.
B) no change occurs.
C) more Fe(s) is produced.
D) more H2O(g) is produced.
E) the equilibrium constant increases.

可以用中文簡單的為我解答一下嗎?謝謝~

Answer 1

答：(D) HSO4– > HF > acetic acid　　因為這三種酸 Ka (pKa = -log[ka])的大小順序就是 HSO4– > HF > acetic acid。答：(D) HF(aq) + H2O(l) --> F–(aq) + H3O+ (aq) 就是 Ka 的表示法！答：(B) ClO-(aq) and Na+(aq).　　因為 HClO 和 NaOH 的莫耳數相等，所以經反應後會全部產生 NaClO。NaClO 在水中的解離方程式如下：　　　NaClO ----> Na+ + ClO- (主要的)　　　ClO- + H2O ----> HClO + OH- (次要的)答：(E) –0.04 V。　　因為 Ecell = Ecathode - Eanode 　　所以 0.84 = 0.80 - Eanode　　　故 Eanode = -0.04 V答：(E) 0.605 atm。　　因為 Kp = [H2][CO]/[H2O]　　所以 3.72 = 1.5x1.5/[H2O]　　　故 [H2O] = 0.605 atm答：(A) the equilibrium concentration of NH4+(aq) is increased.　　因為在化學反應平衡方程式中，　　　NH3 + H2O ----> NH4+ + OH-　　加入 HCl 平衡向右移動，[NH4+] 濃度變大！答：(B) no change occurs. 　　因在下列的化學平衡反應方程式中，　　　3Fe(s) + 4H2O(g) b 4H2(g) + Fe3O4(s)　　H2O和H2的係數相等，所以加大壓力對方程式的平衡沒有影響！