August 2008 Chemistry Regents #41-50

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

 

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Questions

Answer Explanations
41 Which compound is a member of the same homologous series as C3H8?
(1) CH4     (3) C5H8
(2) C4H8   (4) C6H10
1 CnH2n+2  alkane
42 Which equation represents an oxidation reduction reaction?
(1) CH4 + 2O2 ==> CO2 + 2H2O
(2) H2SO4 + Ca(OH)2  ==> CaSO4 + 2H2O
(3) MgCrO4 + BaCl2  ==> MgCl2 + BaCrO4
(4) Zn(NO3)2 + Na2CO3 ==> 2NaNO3 + ZnCO3
1 look for the free element  (O2)  ox # of zero
43 Given the balanced equation representing a reaction:
2KClO3(s) ==> 2KCl(s) + 3O2(g)
The oxidation state of chlorine in this reaction changes from
(1) -1 to +1   (3) +1 to -1
(2) -1 to +5   (4) +5 to -1
4 KClO3 K+1 O3x(-2) so Cl is +5

KCl  K+1 so Cl is -1

3 since it is endothermic delta H is +

since it is one box of a difference from beginning to end (heat of reaction) deltaH is +40

45 Given the balanced equation representing a reaction occurring in an electrolytic cell:
2NaCl(l)==> 2Na(l) + Cl2(g)
Where is Na(l) produced in the cell?
(1) at the anode, where oxidation occurs
(2) at the anode, where reduction occurs
(3) at the cathode, where oxidation occurs
(4) at the cathode, where reduction occurs
4 since Na+ forms Na,

charge goes down, reduction

RED CAT

46 Given the balanced equation representing a reaction:
NH3(g) + H2O(l) ==>NH4+(aq) + OH-(aq)
According to one acid-base theory, the NH3(g) molecules act as
(1) an acid because they accept H+ ions
(2) an acid because they donate H+ ions
(3) a base because they accept H+ ions
(4) a base because they donate H+ ions
3 it gains an H+ so it is a base
47 What volume of 0.120 M HNO3(aq) is needed to completely neutralize 150.0 milliliters of 0.100 M NaOH(aq)?
(1) 62.5 mL   (3) 180. mL
(2) 125 mL    (4) 360. mL
2 MV=MV

0.120M=150.0(0.100)

4 add up all the top numbers on the left

add up all the bottom numbers

left side equals right side

find the missing piece

49 An original sample of the radioisotope fluorine-21 had a mass of 80.0 milligrams. Only 20.0 milligrams of this original sample remain unchanged after 8.32 seconds. What is the half-life of fluorine-21?
(1) 1.04 s   (3) 4.16 s
(2) 2.08 s   (4) 8.32 s
3 80-->40-->20  2 half lives

8.32s/2

50 Which nuclide is paired with a specific use of that nuclide?
(1) carbon-14, treatment of cancer
(2) cobalt-60, dating of rock formations
(3) iodine-131, treatment of thyroid disorders
(4) uranium-238, dating of once-living organisms
3 just memorize them

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

 
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