How can clock reactions (e.g. iodide and thiosulfate) be used to measure initial rate?
As the change in concentration is fixed (2 step - I- + H2O2 then I2 + S2O32-. When all S2O32- used up, I2 remains and turns starch blue-black.)
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When is the end point of a clock reaction?
When one limited reactant runs out. This often results in a sudden colour change.
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What is the independent variable?
The concentration of one of the reactants.
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What is the dependent variable?
Initial rate of reaction
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What is the initial rate of reaction used to calculate?
The order of reaction w.r.t. the element of which the conc. was varied.
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How can the order of reaction w.r.t. a reactant be determined graphically? *
Take logs of both sides of the rate equation: Rate = k[Y]^n, log(rate) = log k + n x log[Y]. Y=mx+c, so when y=log(rate) & x=log[Y], gradient=order n.
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Which concentrations and which times will have the largest % errors?
High concentrations with fast times. Lower times mean that any uncertainty in the time makes up a larger % of the total time.
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What 6 methods can be used to investigate rates of reaction? *
1) Measurement of change in mass 2) Change in volume of gas 3) Titrating samples of reaction mixture 4) Colorimetry 5) Change in electrical conductivity 6) Change in optical activity.
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Other cards in this set
Card 2
Front
When is the end point of a clock reaction?
Back
When one limited reactant runs out. This often results in a sudden colour change.
Card 3
Front
What is the independent variable?
Back
Card 4
Front
What is the dependent variable?
Back
Card 5
Front
What is the initial rate of reaction used to calculate?
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