Regents Chemistry Exam Explanations June 2008

June 2008 Chemistry Regents #21-30

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Questions 1-10 Questions 11-20 Questions 21-30 Questions 31-40 Questions 41-50

Questions
Answer Explanations
21 How is a chemical reaction affected by the addition of a catalyst?
(1) The activation energy decreases.
(2) The heat of reaction increases.
(3) The number of collisions between particles decreases.
(4) The potential energy of the reactants increases. 1 Catalyst-lowers act. energy
22 Systems in nature tend to undergo changes toward
(1) lower energy and less disorder
(2) lower energy and more disorder
(3) higher energy and less disorder
(4) higher energy and more disorder 2 exothermic and increase in entropy
23 What can be concluded if an ion of an element is smaller than an atom of the same element?
(1) The ion is negatively charged because it has fewer electrons than the atom.
(2) The ion is negatively charged because it has more electrons than the atom.
(3) The ion is positively charged because it has fewer electrons than the atom.
(4) The ion is positively charged because it has more electrons than the atom. 3 ions are smaller when they have lost an electron
24 Which class of organic compounds has molecules that contain nitrogen atoms?
(1) alcohol        (3) ether
(2) amine          (4) ketone 2 TABLE R
25 Which two compounds have the same molecular formula but different chemical and physical properties?
(1) CH₃CH₂Cl and CH₃CH₂Br
(2) CH₃CHCH₂ and CH₃CH₂CH₃
(3) CH₃CHO and CH₃COCH₃
(4) CH₃CH₂OH and CH₃OCH₃ 4 count atoms they have to have the same number
just a different arrangement
26 Which half-reaction equation represents the
reduction of a potassium ion?
(1) K⁺ + e^-- ==>K    (3) K⁺ ==>K + e^--
(2) K + e^--==> K⁺    (4) K==> K⁺ + e^-- 1 charge goes down
electron on the more positive side
27 According to the Arrhenius theory, an acid is asubstance that
(1) changes litmus from red to blue
(2) changes phenolphthalein from colorless to pink
(3) produces hydronium ions as the only positive ions in an aqueous solution
(4) produces hydroxide ions as the only negative ions in an aqueous solution 3 acid H⁺
base OH^-

28 Which type of reaction occurs when a high energy particle collides with the nucleus of an atom, converting that atom to an atom of a different element?
(1) addition            (3) substitution
(2) neutralization    (4) transmutation 4 definition of transmutation
29 Which particle is emitted when an atom of 85Kr spontaneously decays?
(1) an alpha particle    (3) a neutron
(2) a beta particle       (4) a proton 2 Use Decay Mode from Table N
30 What is a problem commonly associated with nuclear power facilities?
(1) A small quantity of energy is produced.
(2) Reaction products contribute to acid rain.
(3) It is impossible to control nuclear fission.
(4) It is difficult to dispose of wastes 4 Use your brian
Questions 1-10 Questions 11-20 Questions 21-30 Questions 31-40 Questions 41-50

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Questions	Answer	Explanations
21 How is a chemical reaction affected by the addition of a catalyst? (1) The activation energy decreases. (2) The heat of reaction increases. (3) The number of collisions between particles decreases. (4) The potential energy of the reactants increases.	1	Catalyst-lowers act. energy
22 Systems in nature tend to undergo changes toward (1) lower energy and less disorder (2) lower energy and more disorder (3) higher energy and less disorder (4) higher energy and more disorder	2	exothermic and increase in entropy
23 What can be concluded if an ion of an element is smaller than an atom of the same element? (1) The ion is negatively charged because it has fewer electrons than the atom. (2) The ion is negatively charged because it has more electrons than the atom. (3) The ion is positively charged because it has fewer electrons than the atom. (4) The ion is positively charged because it has more electrons than the atom.	3	ions are smaller when they have lost an electron
24 Which class of organic compounds has molecules that contain nitrogen atoms? (1) alcohol (3) ether (2) amine (4) ketone	2	TABLE R
25 Which two compounds have the same molecular formula but different chemical and physical properties? (1) CH₃CH₂Cl and CH₃CH₂Br (2) CH₃CHCH₂ and CH₃CH₂CH₃ (3) CH₃CHO and CH₃COCH₃ (4) CH₃CH₂OH and CH₃OCH₃	4	count atoms they have to have the same number just a different arrangement
26 Which half-reaction equation represents the reduction of a potassium ion? (1) K⁺ + e^-- ==>K (3) K⁺ ==>K + e^-- (2) K + e^--==> K⁺ (4) K==> K⁺ + e^--	1	charge goes down electron on the more positive side
27 According to the Arrhenius theory, an acid is asubstance that (1) changes litmus from red to blue (2) changes phenolphthalein from colorless to pink (3) produces hydronium ions as the only positive ions in an aqueous solution (4) produces hydroxide ions as the only negative ions in an aqueous solution	3	acid H⁺ base OH^-
28 Which type of reaction occurs when a high energy particle collides with the nucleus of an atom, converting that atom to an atom of a different element? (1) addition (3) substitution (2) neutralization (4) transmutation	4	definition of transmutation
29 Which particle is emitted when an atom of 85Kr spontaneously decays? (1) an alpha particle (3) a neutron (2) a beta particle (4) a proton	2	Use Decay Mode from Table N
30 What is a problem commonly associated with nuclear power facilities? (1) A small quantity of energy is produced. (2) Reaction products contribute to acid rain. (3) It is impossible to control nuclear fission. (4) It is difficult to dispose of wastes	4	Use your brian