21. Which of the following is the best definition of a catalyst?
A) a catalyst is a material which speeds up the rate of a chemical reaction
B) a catalyst is a material which speeds up the rate of a chemical reaction without being used up during the reaction
C) a catalyst is a material which speeds up the rate of a chemical reaction without participating in the reaction
D) all of the above are equally good definitions
24. What is(are) proper name(s) for H3O+?
A) hydrogen ion
B) heavy water
C) hydronium ion
D) all of these
25. Which of the following occurs when NaOH is dissolved in water to form a basic solution?
A) NaOH breaks up to form Na+(aq) and OH-(aq)
B) a complex between NaOH and water is formed
C) the water molecule loses an H+
D) NaOH breaks up to form Na+(aq), H+(aq) and O2-(aq)
31. Which of the following is a strong acid?
A) 0.001 M HCl
B) 3 M CH3COOH
C) both (a) and (b)
D) none of these
32. Which of the following is not a base?
A) HPO42-
B) OH-
C) NH3
D) none, they are all bases
33. Which of the following species is the most important amphiprotic substance in Table 9.2?
A) H2O
B) hydroxide ion
C) HI
D) hydronium ion
34. How many protons can be lost by acetic acid, CH3COOH?
A) 1
B) 2
C) 3
D) 4
36. Which of the following materials will react with an acid to produce a gas?
A) NaOH(aq)
B) Na2CO3(aq)
C) both (a) and (b)
D) neither a nor b
37. Which of the following is true of pure water?
A) pure water contains more hydrogen ions than hydroxide ions
B) pure water is an electrolyte
C) pure water contains equal amounts of hydrogen ions and hydroxide ions
D) pure water contains no hydrogen ions or hydroxide ions
49. An HCl solution has a pH of 3.10, what is the [OH-] in this solution?
A) 7.9 x 10-18 M
B) 1.3 x10-11M
C) 7.9 x10-4 M
D) 1.3 x103 M
Chemistry MC 急急急急 +20
2009-06-10 12:31 pm
回答 (2)
2009-06-11 1:38 am
✔ 最佳答案
21. No good answer.The definition of a catalyst is that :
"Catalyst of a reaction is substance which speeds up the rate of chemical reaction but is chemical unchanged at the end of the reaction."
A is an incomplete definition.
In B, the phrase "without being used up" means some catalyst is consumed (chemically changed). This is false.
In C, catalyst participates in the reaction. If not, how can the catalyst speed up the reaction rate.
24. C
A is H+, B is D2O and C is H3O+.
25. A
NaOH solid contains well-arranged lattice of Na+ and OH- ions. When it dissolves in water, the ions becomes mobile Na+(aq) and OH-(aq) ions. The basic properties of the solution is due to the presence of mobile OH-(aq) ions.
31. A
In 0.001 M HCl, the HCl is completely ionized to form H+(aq) and Cl-(aq) ions. In 3 M CH3COOH(aq), about 0.25% of CH3COOH molecules is ionized to form H+(aq) and CH3COO-(aq) ions.
32. D
All of them can act as bases to accept H+(aq):
HPO42-(aq) + H+(aq) → H2PO4-(aq)
OH-(aq) + H+(aq) → H2O(l)
NH3(aq) + H+(aq) → NH4+(aq)
33. A
Amphoteric substance can act as both an acid and a base.
H2O acting as an acid to release H+: H2O(l) ≒ OH-(aq) + H+(aq)
H2O acting as a base to gain H+: H2O(l) + H+(aq) ≒ H3O+(aq)
34. A
CH3COOH can lose one proton (H+) to give CH3COO-.
36. B
Acid solutions can react with Na2CO3(aq) to give carbon dioxide gas.
CO32-(aq) + 2H+(aq) → H2O(l) + CO2(g)
37. C
At 25oC, pure water contains 1 x 10-7 M of H+(aq) and 1 x 10-7 M of OH-(aq).
49. B
[H+] = 10-pH = 10-3.1 = 7.9 x 10-4 M
[OH-] = Kw/[H+] = (1 x 1014)/(7.9 x 10-4) = 1.3 x 10-11 M
=
2009-06-10 8:31 pm
21 c 24c 25a
31a 32a 33d 34a 36B 37C (high-level ans), D(low-level ans)
49 N/A
31a 32a 33d 34a 36B 37C (high-level ans), D(low-level ans)
49 N/A
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