August 2002  Chemistry Regents #41-50

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

 

Questions

Answer Explanations
41 According to Table I, which potential energy diagram
best represents the reaction that forms
H2O(l) from its elements?

1 DH is negative, exothermic
42 Which structural formula is incorrect? 4 central carbon is bonded 5 times
4 add the top number and bottom numbers

44 The vapor pressure of a liquid is 0.92 atm at 60C. The normal boiling point of the liquid could be

(1) 35C   (3) 55C

(2) 45C    (4) 65C

4 since it is a liquid at 60C it must boil at a higher temp
45 When 50. milliliters of an HNO3 solution is
exactly neutralized by 150 milliliters of a 0.50 M
solution of KOH, what is the concentration of
HNO3?
(1) 1.0 M     (3) 3.0 M
(2) 1.5 M     (4) 0.5 M
2 MV=MV

(150mL x 0.50M)/50mL =

46 In Period 3, from left to right in order, each successive
element will
(1) decrease in electronegativity
(2) decrease in atomic mass
(3) increase in number of protons
(4) increase in metallic character
3 Table S
2 2 balance it
48 One hundred grams of water is saturated with
NH4Cl at 50C. According to Table G, if the
temperature is lowered to 10C, what is the total
amount of NH4Cl that will precipitate?
(1) 5.0 g     (3) 30. g
(2) 17 g      (4) 50. g
2 subtract the amount at 50C from the amount at 10C

52-34= 18grams close enough

49 What is the total number of grams of NaI(s)
needed to make 1.0 liter of a 0.010 M solution?
(1) 0.015    (3) 1.5
(2) 0.15      (4) 15
3 2 parter  M=mol/L

mol=grams /gram formula mass

50 Given the reaction:
2 H2(g) + O2(g)-->2 H2O(l) + 571.6 kJ
What is the approximate DH for the formation of
1 mole of H2O(l)?
(1) .285.8 kJ     (3) .571.6 kJ
(2) +285.8 kJ    (4) +571.6 kJ
1 DH is negative exothermic

for 1 mole 285.6kJ is released

that reaction is for 2 moles of water

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