August 2008 Chemistry Regents #4150
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Questions 
Answer  Explanations 
41 Which compound is a member of the same
homologous series as C_{3}H_{8}? (1) CH_{4} (3) C_{5}H_{8} (2) C_{4}H_{8} (4) C_{6}H_{10} 
1  C_{n}H_{2n+2} alkane 
42 Which equation represents an oxidation reduction
reaction? (1) CH_{4} + 2O_{2} ==> CO_{2} + 2H_{2}O (2) H_{2}SO_{4} + Ca(OH)_{2} ==> CaSO_{4} + 2H_{2}O (3) MgCrO_{4} + BaCl_{2} ==> MgCl_{2} + BaCrO_{4} (4) Zn(NO_{3})_{2} + Na_{2}CO_{3} ==> 2NaNO_{3} + ZnCO_{3} 
1  look for the free element (O_{2}) ox # of zero 
43 Given the balanced equation representing a
reaction: 2KClO_{3(s)} ==> 2KCl_{(s)} + 3O_{2(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  KClO_{3 }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)} + Cl_{2(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: NH_{3(g)} + H_{2}O_{(l)} ==>NH_{4}^{+}_{(aq)} + OH^{}_{(aq)} According to one acidbase theory, the NH_{3(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 HNO_{3(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
fluorine21 had a mass of 80.0 milligrams. Only
20.0 milligrams of this original sample remain
unchanged after 8.32 seconds. What is the
halflife of fluorine21? (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) carbon14, treatment of cancer (2) cobalt60, dating of rock formations (3) iodine131, treatment of thyroid disorders (4) uranium238, dating of onceliving organisms 
3  just memorize them 
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