August 2015 Chemistry Regents #83-85

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Question 83-85

 

  Base your answers to questions 83 through 85 on the information below and on your knowledge of chemistry.

 Early scientists defined oxidation as a chemical reaction in which oxygen combined with another element to produce an oxide of the element. An example of oxidation based on this definition is the combustion of methane. This reaction is represented by the balanced equation below.

 Equation 1:    CH4(g)  + 2O2(g) → CO2(g) + 2H2O(g)

The definition of oxidation has since been expanded to include many reactions that do not involve oxygen. An example of oxidation based on this expanded definition is the reaction between magnesium ribbon and powdered sulfur when heated in a crucible. This reaction is represented by the balanced equation below.

Equation 2:    Mg(s) + S(s) → MgS(s)

83 State why early scientists classified the reaction represented by equation 1 as oxidation. [1]

Answer--> Oxides are formed.

A substance reacts with oxygen.Zn to the Cu.....Right

84 Determine the change in oxidation number of carbon in equation 1. [1]

Answer-->from -4 to +4

85 Write a balanced half-reaction equation for the oxidation that occurs in the reaction represented by equation 2. [1]

Answer-->Mg → Mg2+ + 2e-

Conversion Table Aug 2015

raw score (out of 85) scale score (your grade)
79 91
78 89
74 85
70 80
50 65

Other Regents Exams

 

 

Questions 1-5 Questions 6-10 Questions 11-15 Questions 16-20 Questions 21-25 Questions 26-30 Questions 31-35 Questions 36-40 Questions 41-45 Questions 46-50

Questions 51-54 Questions 55-57 Questions 58-59 Questions 60-61 Questions 62-65 Questions 66-68 Questions 69-72 Questions 73-74  Questions 75-76  Questions 77-78  Questions 79-80  Questions 81-82  Questions 83-85

 

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