Regents Chemistry Exam Explanations June 2007

June 2007 Chemistry Regents #11-20

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

Questions
Answer Explanations
11 An oxygen molecule contains a double bond because the two atoms of oxygen share a total of
(1) 1 electron      (3) 3 electrons
(2) 2 electrons    (4) 4 electrons 4 each bond is 2 electrons shared
12 Which term is defined as a measure of the average kinetic energy of the particles in a sample?
(1) temperature   (3) thermal energy
(2) pressure        (4) chemical energy 1 temperature definition
13 A 3.0 M HCl_(aq) solution contains a total of
(1) 3.0 grams of HCl per liter of water
(2) 3.0 grams of HCl per mole of solution
(3) 3.0 moles of HCl per liter of solution
(4) 3.0 moles of HCl per mole of water 3 Table T
M=Molarity=mol/L
14 A dilute, aqueous potassium nitrate solution is best classified as a
(1) homogeneous compound
(2) homogeneous mixture
(3) heterogeneous compound
(4) heterogeneous mixture 2 solution==> homogeneous mixture
3 equilibrium
concentrations are constant and rates are equal
16 A 5.0-gram sample of zinc and a 50.-milliliter sample of hydrochloric acid are used in a chemical reaction. Which combination of these samples has the fastest reaction rate?
(1) a zinc strip and 1.0 M HCl_(aq)
(2) a zinc strip and 3.0 M HCl_(aq)
(3) zinc powder and 1.0 M HCl_(aq)
(4) zinc powder and 3.0 M HCl_(aq) 4 large surface area ==>powder
high concentration 3.0M vs 1.0M
17 For a given reaction, adding a catalyst increases the rate of the reaction by
(1) providing an alternate reaction pathway that has a higher activation energy
(2) providing an alternate reaction pathway that has a lower activation energy
(3) using the same reaction pathway and increasing the activation energy
(4) using the same reaction pathway and decreasing the activation energy 2 catalyst lowers the activation energy, creating a different pathway
18 Which reaction releases the greatest amount of energy per 2 moles of product?
(1) 2CO_(g) + O_2(g)==> 2CO_2(g)
(2) 4Al_(s) + 3O_2(g) ==>2Al₂O_3(s)
(3) 2H_2(g) + O_2(g)==> 2H₂O_(g)
(4) N_2(g) + 3H_2(g) ==>2NH_3(g) 2 Use Table H
19 What is the total number of carbon atoms in a molecule of ethanoic acid?
(1) 1    (3) 3
(2) 2    (4) 4 2 eth 2 carbons
4 different structures have different properties
Questions 1-10 Questions 11-20 Questions 21-30 Questions 31-40 Questions 41-50

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Questions	Answer	Explanations
11 An oxygen molecule contains a double bond because the two atoms of oxygen share a total of (1) 1 electron (3) 3 electrons (2) 2 electrons (4) 4 electrons	4	each bond is 2 electrons shared
12 Which term is defined as a measure of the average kinetic energy of the particles in a sample? (1) temperature (3) thermal energy (2) pressure (4) chemical energy	1	temperature definition
13 A 3.0 M HCl_(aq) solution contains a total of (1) 3.0 grams of HCl per liter of water (2) 3.0 grams of HCl per mole of solution (3) 3.0 moles of HCl per liter of solution (4) 3.0 moles of HCl per mole of water	3	Table T M=Molarity=mol/L
14 A dilute, aqueous potassium nitrate solution is best classified as a (1) homogeneous compound (2) homogeneous mixture (3) heterogeneous compound (4) heterogeneous mixture	2	solution==> homogeneous mixture
	3	equilibrium concentrations are constant and rates are equal
16 A 5.0-gram sample of zinc and a 50.-milliliter sample of hydrochloric acid are used in a chemical reaction. Which combination of these samples has the fastest reaction rate? (1) a zinc strip and 1.0 M HCl_(aq) (2) a zinc strip and 3.0 M HCl_(aq) (3) zinc powder and 1.0 M HCl_(aq) (4) zinc powder and 3.0 M HCl_(aq)	4	large surface area ==>powder high concentration 3.0M vs 1.0M
17 For a given reaction, adding a catalyst increases the rate of the reaction by (1) providing an alternate reaction pathway that has a higher activation energy (2) providing an alternate reaction pathway that has a lower activation energy (3) using the same reaction pathway and increasing the activation energy (4) using the same reaction pathway and decreasing the activation energy	2	catalyst lowers the activation energy, creating a different pathway
18 Which reaction releases the greatest amount of energy per 2 moles of product? (1) 2CO_(g) + O_2(g)==> 2CO_2(g) (2) 4Al_(s) + 3O_2(g) ==>2Al₂O_3(s) (3) 2H_2(g) + O_2(g)==> 2H₂O_(g) (4) N_2(g) + 3H_2(g) ==>2NH_3(g)	2	Use Table H
19 What is the total number of carbon atoms in a molecule of ethanoic acid? (1) 1 (3) 3 (2) 2 (4) 4	2	eth 2 carbons
	4	different structures have different properties