Regents Chemistry Exam Explanations June 2005

June 2005 Chemistry Regents #11-20

Highlight to reveal answers and explanations

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

Questions
Answer Explanations
11 As a chlorine atom becomes a negative ion, the atom
(1) gains an electron and its radius increases
(2) gains an electron and its radius decreases
(3) loses an electron and its radius increases
(4) loses an electron and its radius decreases 1 nonmetals gain electrons and will get bigger
12 Based on Reference Table S, the atoms of which of these elements have the strongest attraction for electrons in a chemical bond?
(1) N       (3) P
(2) Na     (4) Pt 1 Definition-electronegativity
13 Which terms are used to identify pure substances?
(1) an element and a mixture
(2) an element and a compound
(3) a solution and a mixture
(4) a solution and a compound 2 Substance-elements and compounds
14 The solubility of KClO_3(s) in water increases as the
(1) temperature of the solution increases
(2) temperature of the solution decreases
(3) pressure on the solution increases
(4) pressure on the solution decreases 1 Table G- as temperature increases
15 Compared to a 0.1 M aqueous solution of NaCl, a 0.8 M aqueous solution of NaCl has a
(1) higher boiling point and a higher freezing point
(2) higher boiling point and a lower freezing point
(3) lower boiling point and a higher freezing point
(4) lower boiling point and a lower freezing point 2 BOILING PT GOES UP
freezing point goes down
16 The kinetic molecular theory assumes that the particles of an ideal gas
(1) are in random, constant, straight-line motion
(2) are arranged in a regular geometric pattern
(3) have strong attractive forces between them
(4) have collisions that result in the system losing energy 1 Ideal gas rule
17 In which process does a solid change directly into a vapor?
(1) condensation    (3) deposition
(2) sublimation       (4) solidification 2 Definition of sublimation
18 Which statement must be true about a chemical system at equilibrium?
(1) The forward and reverse reactions stop.
(2) The concentration of reactants and products are equal.
(3) The rate of the forward reaction is equal to the rate of the reverse reaction.
(4) The number of moles of reactants is equal to the number of moles of product. 3 Concentrations constant or rates are equal
19 Adding a catalyst to a chemical reaction results in
(1) a decrease in activation energy and a decrease in the reaction rate
(2) a decrease in activation energy and an increase in the reaction rate
(3) an increase in activation energy and a decrease in the reaction rate
(4) an increase in activation energy 2 activation energy decreases and reaction rate increases
20 Systems in nature tend to undergo changes toward
(1) lower energy and lower entropy
(2) lower energy and higher entropy
(3) higher energy and lower entropy
(4) higher energy and higher entropy 2 nature is exothermic (loses energy) and becomes more random (entropy)
Questions 1-10 Questions 11-20 Questions 21-30 Questions 31-40 Questions 41-50

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Questions	Answer	Explanations
11 As a chlorine atom becomes a negative ion, the atom (1) gains an electron and its radius increases (2) gains an electron and its radius decreases (3) loses an electron and its radius increases (4) loses an electron and its radius decreases	1	nonmetals gain electrons and will get bigger
12 Based on Reference Table S, the atoms of which of these elements have the strongest attraction for electrons in a chemical bond? (1) N (3) P (2) Na (4) Pt	1	Definition-electronegativity
13 Which terms are used to identify pure substances? (1) an element and a mixture (2) an element and a compound (3) a solution and a mixture (4) a solution and a compound	2	Substance-elements and compounds
14 The solubility of KClO_3(s) in water increases as the (1) temperature of the solution increases (2) temperature of the solution decreases (3) pressure on the solution increases (4) pressure on the solution decreases	1	Table G- as temperature increases
15 Compared to a 0.1 M aqueous solution of NaCl, a 0.8 M aqueous solution of NaCl has a (1) higher boiling point and a higher freezing point (2) higher boiling point and a lower freezing point (3) lower boiling point and a higher freezing point (4) lower boiling point and a lower freezing point	2	BOILING PT GOES UP freezing point goes down
16 The kinetic molecular theory assumes that the particles of an ideal gas (1) are in random, constant, straight-line motion (2) are arranged in a regular geometric pattern (3) have strong attractive forces between them (4) have collisions that result in the system losing energy	1	Ideal gas rule
17 In which process does a solid change directly into a vapor? (1) condensation (3) deposition (2) sublimation (4) solidification	2	Definition of sublimation
18 Which statement must be true about a chemical system at equilibrium? (1) The forward and reverse reactions stop. (2) The concentration of reactants and products are equal. (3) The rate of the forward reaction is equal to the rate of the reverse reaction. (4) The number of moles of reactants is equal to the number of moles of product.	3	Concentrations constant or rates are equal
19 Adding a catalyst to a chemical reaction results in (1) a decrease in activation energy and a decrease in the reaction rate (2) a decrease in activation energy and an increase in the reaction rate (3) an increase in activation energy and a decrease in the reaction rate (4) an increase in activation energy	2	activation energy decreases and reaction rate increases
20 Systems in nature tend to undergo changes toward (1) lower energy and lower entropy (2) lower energy and higher entropy (3) higher energy and lower entropy (4) higher energy and higher entropy	2	nature is exothermic (loses energy) and becomes more random (entropy)