January 2007 Chemistry Regents #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
(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
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
(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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