DIY Science: Illustrated Guide to Home Chemistry Experiments: All Lab, No Lecture by Robert Bruce Thompson

Author:Robert Bruce Thompson
Language: eng
Format: mobi, epub
Tags: SCIENCE / Chemistry / General
ISBN: 9780596557959
Publisher: Maker Media, Inc
Published: 2009-06-30T04:00:00+00:00

Laboratory 12.1: Determine the Effect of Temperature on Reaction Rate

Reactions proceed faster at higher temperatures because increasing the temperature also increases the average kinetic energy of the reactant molecules, making it more likely that a collision between two reactant molecules will have sufficient energy to initiate the reaction. An old rule of thumb states that increasing the temperature by 10°C doubles the rate of reaction. (So, of course, reducing the temperature by 10°C halves the reaction rate.)

We’ll test that rule of thumb in this lab by reacting Alka-Seltzer tablets with water at different temperatures. When an Alka-Seltzer tablet is dropped into water, it emits carbon dioxide as it dissolves and its components react. We could get basic data about the reaction rate simply by determining how long it takes a tablet to dissolve completely in water at various temperatures. But using that method gives us data only about the starting and ending points. It doesn’t tell us, other than in the most general terms, whether the reaction rate is linear or if it changes over time.

We know that this reaction evolves gaseous carbon dioxide, which means that the mass of the reaction vessel and contents decreases as the reaction proceeds. By recording the mass of the reaction vessel and its contents periodically as the reaction progresses, we can gather the data needed to determine whether the reaction rate is linear and whether reaction temperature affects the linearity of the reaction rate.

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