January 2004 Regents #4150
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Questions 
Answer  Explanations 
41 What is the Molarity of a solution containing 20 grams
of NaOH in 500 milliliters of solution? (1) 1 M (3) 0.04 M (2) 2 M (4) 0.5 M 
1  mole/Liters
moles=20g/40g=0.5mol 500mL is 0.5L M=0.5mol/0.5L= 1M 
4  indirect relationship  
43 Given the equation: C_{2}H_{6} + Cl_{2} > C_{2}H_{5}Cl + HCl This reaction is best described as (1) addition involving a saturated hydrocarbon (2) addition involving an unsaturated hydrocarbon (3) substitution involving a saturated hydrocarbon (4) substitution involving an unsaturated hydrocarbon 
3  Substitution Saturated 
2  Cu^{2+} is reduced to Cu on
the key
Red Cat 

45 A student neutralized 16.4 milliliters of HCl by adding
12.7 milliliters of 0.620 M KOH. What was the molarity of the HCl acid? (1) 0.168 M (3) 0.620 M (2) 0.480 M (4) 0.801 M 
2  MV=MV M(16.4mL)= (0.620M)(12.7mL) M=0.480M 
46 Nuclear fusion differs from nuclear fission because
nuclear fusion reactions (1) form heavier isotopes from lighter isotopes (2) form lighter isotopes from heavier isotopes (3) convert mass to energy (4) convert energy to mass 
2  H + H> He
fusion (light atoms) U + n> Ba + Kr +3n fission (heavy atoms) 
47 After 32 days, 5 milligrams of an 80milligram sample
of a radioactive isotope remains unchanged. What is the halflife of
this element? (1) 8 days (3) 16 days (2) 2 days (4) 4 days 
1  80>40>20>10>5 4
half lives 32days/4 = 8 days per half life 
48 Which electron configuration represents an atom of chlorine in an excited state? (1) 2–8–7 (3) 2–8–6–1 (2) 2–8–8 (4) 2–8–7–1 
3  17 electrons with 1 promoted 
49 As each successive element in Group 15 of the Periodic
Table is considered in order of increasing atomic number, the atomic
radius (1) decreases (2) increases (3) remains the same 
2  See table S, or atomic snowman o 0 O 
2  adding water causes more KNO_{3}
to dissolve so solid becomes aqueous, entropy increases 
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