18.2 - Concentration-time graphs Flashcards Preview

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Flashcards in 18.2 - Concentration-time graphs Deck (11):

What does a colorimeter do?

Measures light intensity passing through a sample


How do you monitor rate using a colorimeter, once you have prepared your standard solution of coloured chemical?

1) Select an appropriate filter on colorimeter
2) Zero the colorimeter
3) Measure the absorbance readings
4) Plot calibration curve of absorbance against concentration
5) Carry out the reaction, taking absorbance readings at regular intervals
6) Plot a graph of concentration against time
7) Determine order


Describe the different shapes of graphs for different orders on a concentration-time graph

Zero order = straight line, negative gradient
First order = downwards curve, gradually slows
Second order = steeper downwards curve


What would you plot on the x-axis of a concentration-time graph?



What would you plot on the y-axis of a concentration-time graph?



What is a half-life?

The time taken for the concentration of a reactant to decrease by half


What is the symbol for half-life?

t 1/2


How would you calculate the rate constant from the rate?

Draw a tangent on curve at a particular concentration
Calculate gradient of tangent
Rearrange rate equation and substitute in the values


How would you calculate rate constant from the half-life?

k = ln2 / t 1/2


What does the gradient of a zero order concentration-time graph represent?

The rate constant


How would you calculate the rate constant form the rate using a concentration-time graph?

1) Tangent drawn at particular concentration
2) Gradient of tangent = rate
3) k = rate / conc.