January 2010 Chemistry Regents #31-40

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Questions

Answer Link Explanations
31 Which formula represents copper(I) oxide?
(1) CuO     (3) Cu2O
(2) CuO2   (4) Cu2O2
3 Link CuO2-

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
4 Link d=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
3 LinkA

LinkB

X charge is 2+

group 2

2 Link same 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
2 Link use 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
3 Link 200g-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
1 Link reduce 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.
3 Link released 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)
3 Link van'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
1 Link 52g/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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