January 2009 Chemistry Regents #54-55

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Questions

Base your answers to questions 54 through 55 on the information below.

A 4.86-gram sample of calcium reacted completely with oxygen to form 6.80 grams of calcium oxide. This reaction is represented by the balanced equation below.

2Ca(s) + O2(g) ==> 2CaO(s)

54 Determine the total mass of oxygen that reacted. [1]

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Answer==>1.94g

(6.80g-4.86g=1.94g)

55 Explain, in terms of electrons, why the radius of a calcium ion is smaller than the radius of a calcium atom. [1]

HIGHLIGHT TO SEE THE ANSWER

The ion has one less principal energy level than the atom

A Ca2+ ion has two fewer electrons than a Ca atom, so the ion is smaller.

Ca has an electron configuration of 2-8-8-2, and Ca2+ has an electron configuration of 2-8-8, so the ion is smaller.

on to Questions 56-58

 

Questions 1-10 Questions 11-20 Questions 21-30 Questions 31-40 Questions 41-50

Questions 51-53 Questions 54-55 Questions 56-58 Questions 59-61 Questions 62-64 Questions 65-66 Questions 67-68 Questions 69-71 Questions 72-74 Questions 75-77 Questions 78-79 Questions 80-81

 
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