
June 2008 Chemistry Regents #4150
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Questions 
Answer  Explanations 
41 A 1.0gram sample of which element will uniformly fill
a closed 2.0liter container at STP? (1) antimony (3) tellurium (2) sulfur (4) xenon 
4  will uniformly fill==>gas 
42 Given the balanced equation representing a reaction: C_{3}H_{8(g)} + 5O_{2(g)}==>3CO_{2(g)} + 4H_{2}O_{(g)} What is the total number of moles of O_{2(g)} required for the complete combustion of 1.5 moles of C_{3}H_{8(g)}? (1) 0.30 mol (3) 4.5 mol (2) 1.5 mol (4) 7.5 mol 
4  set up a proportion 1.5/1 C_{3}H_{8(g) }= x/5O_{2(g)} 
43 A sample of gas occupies a volume of 50.0 milliliters
in a cylinder with a movable piston. The pressure of the sample is 0.90
atmosphere and the temperature is 298 K. What is the volume of the
sample at STP? (1) 41 mL (3) 51 mL (2) 49 mL (4) 55 mL 
1  PV/T =PV/T 
44 Which solution has the lowest freezing point? (1) 10. g of KI dissolved in 100. g of water (2) 20. g of KI dissolved in 200. g of water (3) 30. g of KI dissolved in 100. g of water (4) 40. g of KI dissolved in 200. g of water 
3  find the largest ratio of KI to water 
45 Which 1mole sample has the least entropy? (1) Br_{2(s)} at 266 K (3) Br_{2(l)} at 332 K (2) Br_{2(l)} at 266 K (4) Br_{2(g)} at 332 K 
1  solid has least entropy 
46 At 20.°C, a 1.2gram sample of Mg ribbon reacts rapidly
with 10.0 milliliters of 1.0 M HCl_{(aq)}. Which change in
conditions would have caused the reaction to proceed more slowly? (1) increasing the initial temperature to 25°C (2) decreasing the concentration of HCl_{(aq)} to 0.1 M (3) using 1.2 g of powdered Mg (4) using 2.4 g of Mg ribbon 
2  less surface area = slower reaction 
47 Which general formula represents the compound CH_{3}CH_{2}CCH? (1) C_{n}H_{n} (3) C_{n}H_{2n–2} (2) C_{n}H_{2n} (4) C_{n}H_{2n+2} 
3  CH_{3}CH_{2}CCH==> C_{4}H_{6} C_{n}H_{2n–2}

48 Which compound dissolves in water to form an aqueous
solution that can conduct an electric current? (1) CCl_{4} (3) CH_{3}COOH (2) C_{2}H_{5}OH (4) CH_{4} 
3  acids bases or salts CH_{3}COOH acetic acid Table K 
49 Given the equation representing a reaction at
equilibrium: NH_{3(g)} + H_{2}O_{(l)} ==>NH_{4}^{+}_{(aq)} + OH^{–}_{(aq)} The H+ acceptor for the forward reaction is (1) H_{2}O_{(l)} (3) NH^{4+}_{(aq)} (2) NH_{3(g) }(4) OH^{–}_{(aq)} 
2  NH_{3(g)} ==>NH_{4}^{+}_{(aq)}
it gained H^{+} 
50 An original sample of K40 has a mass of 25.00 grams.
After 3.9 × 10^{9} years, 3.125 grams of the original sample
remains unchanged. What is the halflife of K40? (1) 1.3 × 10^{9} y (3) 3.9 × 10^{9} y (2) 2.6 × 10^{9} y (4) 1.2 × 10^{10 }y 
1  25==>12.5==>6.25==>3.125 3
half lives 3.9 × 10^{9} years/ 3 
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