January 2010 Chemistry Regents #31-40

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Questions

AnswerLinkExplanations
31 Which formula represents copper(I) oxide?
(1) CuO     (3) Cu2O
(2) CuO2   (4) Cu2O2		3LinkCu+  O2-

2:1 ratio

32 At STP, a 7.49-gram sample of an element has a volume of 1.65 cubic centimeters. The sample is most likely
(1) Ta (3) Te
(2) Tc (4) Ti		4Linkd=m/v    7.49g/1.65cm3

then use Table S to  match up the element

33 Which element, represented by X, reacts with fluorine to produce the compound XF2?
(1) aluminum    (3) magnesium
(2) argon          (4) sodium		3LinkA

LinkB

X charge is 2+

group 2

2Linksame number of protons
35 As atomic number increases within Group 15 on the Periodic Table, atomic radius
(1) decreases, only
(2) increases, only
(3) decreases, then increases
(4) increases, then decreases		2Linkuse table S, more energy levels
36 Given the balanced equation representing a reaction:
CaO(s) + CO2(g) ==>CaCO3(s) + heat
What is the total mass of CaO(s) that reacts completely with 88 grams of CO2(g) to produce 200. grams of CaCO3(s)?
(1) 56 g       (3) 112 g
(2) 88 g       (4) 288 g		3Link200g-88g= 112g

conservation of mass

37 What is the empirical formula of a compound that has a carbon-to-hydrogen ratio of 2 to 6?
(1) CH3 (3) C3H
(2) C2H6 (4) C6H2		1Linkreduce the formula

2-6

1-3

38 Given the balanced equation representing a reaction:
H2(g) + Cl2(g) ==>2HCl(g) + energy
Which statement describes the energy changes in this reaction?
(1) Energy is absorbed as bonds are formed, only.
(2) Energy is released as bonds are broken, only.
(3) Energy is absorbed as bonds are broken, and energy is released as bonds are formed.
(4) Energy is absorbed as bonds are formed, and energy is released as bonds are broken.		3Linkreleased energy is a product, right of the arrow

bonds are broken then formed

39 Which solution has the highest boiling point at standard pressure?
(1) 0.10 M KCl(aq)
(2) 0.10 M K2SO4(aq)
(3) 0.10 M K3PO4(aq)
(4) 0.10 M KNO3(aq)		3Linkvan't Hoff find the one that breaks up into the most particles

KCl-2           K2SO4-3 

K3PO4 -4     KNO3 - 2

40 What is the molarity of 1.5 liters of an aqueous solution that contains 52 grams of lithium fluoride, LiF, (gram-formula mass =26 grams/mole)?
(1) 1.3 M    (3) 3.0 M
(2) 2.0 M    (4) 0.75 M		1Link52g/26g/mol= 2 moles

2 moles/1.5L= 1..3M

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

Questions 51-52 Questions 53-55 Questions 56-57 Questions 58-60 Questions 61-63 Questions 64-65 Questions 66-68 Questions 69-71 Questions 72-75 Questions 76-78 Questions 79-81  Questions 82-84

 
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