January 2007 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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41 At room temperature, a mixture of sand and water can be separated by
(1) ionization       (3) filtration
(2) combustion     (4) sublimation
3 filtering removes solids from liquids
42 Given the balanced equation representing a reaction at 101.3 kPa and 298 K:
N2(g) + 3H2(g) => 2NH3(g) + 91.8 kJ
Which statement is true about this reaction?
(1) It is exothermic and DH equals -91.8 kJ.
(2) It is exothermic and DH equals +91.8 kJ.
(3) It is endothermic and DH equals -91.8 kJ.
(4) It is endothermic and DH equals +91.8 kJ.
1 it is exothermic so delta H is negative
43 Which balanced equation represents a phase equilibrium?
(1) H2(g) + I2(g)<==> 2HI(g)
(2) 2NO2(g) <==> N2O4(g)
(3) Cl2(g) <==> Cl2(l)
(4) 3O2(g)<==>  2O3(g)
3 phase equilibrium is a phase change

NOT a REACTION

44 Given the system at equilibrium:
2POCl3(g) + energy <==> 2PCl3(g) + O2(g)
Which changes occur when O2(g) is added tothis system?
(1) The equilibrium shifts to the right and the concentration of PCl3(g) increases.
(2) The equilibrium shifts to the right and the concentration of PCl3(g) decreases.
(3) The equilibrium shifts to the left and the concentration of PCl3(g) increases.
(4) The equilibrium shifts to the left and the concentration of PCl3(g) decreases.
4 adding a PRODUCT shift the equilibrium to the left

the reactants increase in concentration and the products decrease

45 What is the oxidation number of chromium in the chromate ion, CrO42?
(1) +6   (3) +3
(2) +2   (4) +8
1 each oxygen is 2-  (4 x2-)= -8

it adds up to -2    =-8 +X

46 Given the balanced equation representing a reaction:
H2SO4(aq) + 2KOH(aq) =>K2SO4(aq) + 2H2O(l)
Which type of reaction is represented by this equation?
(1) decomposition      (3) single replacement
(2) neutralization          (4) synthesis
2 acid and base= neutralization
47 In which 0.01 M solution is phenolphthalein pink?
(1) CH3OH(aq)    (3) CH3COOH(aq)
(2) Ca(OH)2(aq)   (4) HNO3(aq)
2 bases are pink,  look for OH  or table L
48 As the pH of a solution is changed from 3 to 6, the concentration of hydronium ions
(1) increases by a factor of 3
(2) increases by a factor of 1000
(3) decreases by a factor of 3
(4) decreases by a factor of 1000
4 for each pH change it is 10xs stronger, pH changes by 3 it is 1000x's

hydronium determines acidity so it decreases when pH increases

1 1/8 is 3 half lives

34.5/3 = 11.5minutes per half life

1 find the missing masses

 look at table O for the particle

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