January 2009 Chemistry Regents #69-71

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Questions

Base your answers to questions 69 through 71 on the information below.

In a laboratory, 0.100 mole of colorless hydrogen iodide gas at room temperature is placed in a 1.00-liter flask. The flask is sealed and warmed, causing the HI(g) to start decomposing to H2(g) and I2(g). Then the temperature of the contents of the flask is kept constant.

During this reaction, the contents of the flask change to a pale purple-colored mixture of HI(g), H2(g), and I2(g). When the color of the mixture in the flask stops changing, the concentration of I2(g) is determined to be 0.013 mole per liter. The relationship between concentration and time for the reactant and products is shown in the graph below.

69 Write a balanced equation to represent the decomposition reaction occurring in the flask. [1]

HIGHLIGHT TO SEE THE ANSWER

2HI ==>I2 + H2

70 State, in terms of concentration, evidence that indicates the system in the flask has reached equilibrium. [1]

HIGHLIGHT TO SEE THE ANSWER

"concentrations are constant"

The concentration of each product and the concentration of the reactant remain the same.

71 Calculate the mass of I2(g) in the flask at equilibrium. Your response must include both a correct numerical setup and the calculated result. [2]

HIGHLIGHT TO SEE THE ANSWER

SET UP   126.905 2 = 253.810 g/mol

(0.013 M)(1.00 L)(253.810 g/mol)

mass = 0.013 254

ANSWER==>3.3 g

on to Questions 72-74

 

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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