January 2012 Chemistry Regents #66-69

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Question

Base your answers to questions 66 through 69 on the information below.

 

During a fireworks display, salts are heated to very high temperatures. Ions in the salts absorb energy and become excited. Spectacular colors are produced as energy is emitted from the ions in the form of light.

The color of the emitted light is characteristic of the metal ion in each salt. For example, the lithium ion in lithium carbonate, Li2CO3, produces a deep-red color. The strontium ion in strontium carbonate, SrCO3,  produces a bright-red color. Similarly, calcium chloride is used for orange light, sodium chloride for yellow light, and barium chloride for green light.

66 Write the formula for the salt used to produce green light in a fireworks display. [1]

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BaCl2

67 Identify the two types of chemical bonds found in the salt used to produce a deep-red color. [1]

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ionic and covalent

or

ionic and polar covalent

68 Determine the oxidation state of carbon in the salt used to produce:1 bright- red color. [1]

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+4

69 Explain, in terms of subatomic particles and energy states, how the colors in a fireworks display are produced. [1]

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When electrons in the ions move from higher energy levels to lower energy states, lights of specific wavelengths are emitted .

or

Light is emitted when electrons return from higher electron shells to lower electron shells.

on to Questions 70-71

  

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