June 2010 Chemistry Regents #69-71

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

At room temperature, a reaction occurs when KIO3(aq) is mixed with NaHSO3(aq) that contains a small amount of starch. The colorless reaction mixture turns dark blue after a period of time that depends on the concentration of the reactants. In a laboratory, 12 drops of a 0.02 M NaHSO3(aq) solution containing starch were placed in each of six test tubes. A different number of drops of 0.02 M KIO3(aq) and enough water to maintain a constant volume were added to each test tube and the time for the dark-blue color to appear was measured. The data were recorded in the table below.

69 On the grid in your answer booklet:

• Mark an appropriate scale on the axis labeled “Time (s).” [1]

• Plot the data from the data table. Circle and connect the points. [1]

Answer to Question #69

70 State how increasing the number of drops of 0.02 M KIO3(aq) used in the reaction affects the rate of reaction. [1]

HIGHLIGHT TO SEE THE ANSWER

NOTE=The time decreases when there are more drops, so the rate is increasing.

Increasing the number of drops of KIO3(aq) increases the rate of reaction.

The reaction takes less time if more drops of KIO3 are used.

The reaction occurs faster.

71 Identify one factor, other than the concentration of the reactants, that would affect the rate of this reaction. [1]

HIGHLIGHT TO SEE THE ANSWER

the temperature of the reactants

a catalyst

Wrong Answer=surface area (no solids)

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