January 2009 Chemistry Regents #72-74

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Base your answers to questions 72 through 74 on the information below.

Soil pH can affect the development of plants. For example, a hydrangea plant produces blue flowers when grown in acidic soil but pink flowers when grown in basic soil. Evergreen plants can show a yellowing of foliage, called chlorosis, when grown in soil that is too basic.

Acidic soil can be neutralized by treating it with calcium hydroxide, Ca(OH)2, commonly called slaked lime. Slaked lime is slightly soluble in water.

72 Compare the hydrogen ion concentration to the hydroxide ion concentration in soil when a hydrangea plant produces pink flowers. [1]

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The hydroxide ion concentration is greater than the hydrogen ion concentration.

The H3O+ concentration is less than the OH- concentration.

[OH-] > [H3O+]

73 An evergreen plant has yellowing foliage. The soil surrounding the plant is tested with methyl orange and bromthymol blue. Both indicators turn yellow in the soil tests. State, in terms of pH value, why the yellowing of the plant is not due to chlorosis. [1]

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The pH is between 4.4 and 6.0, which indicates an acidic soil.

The pH of the soil surrounding the plant is below 6.0.

For chlorosis, the soil pH must be above 7.

74 Write an equation, using symbols or words, for the neutralization of the ions in acidic soil by the ions released by slaked lime in water. [1]

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H+ + OH- ==>HOH

H3O+ + OH- => 2H2O

hydrogen ions + hydroxide ions => water

hydroxide ions + hydronium ions => water

(It is on Table I)

on to Questions 75-77

 

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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