Effect of a Catalyst on Reaction Rate

This video is owned by the Journal of Chemical Education. Copyright © ACS Division of Chemical Education, Inc. Only subscribers to JCE Web Software can view this video. Allowed uses

Summary

When a solution of pink Co(II) catalyst is poured into solutions containing tartrate ion and hydrogen peroxide, the solution turns green and bubbles of carbon dioxide are produced. In the absence of the Co(II) catalyst, no reaction occurs. The 28 thumbnail images summarize the content of the video. Click an image to see the image gallery.

Narration

Four vials contain sodium potassium tartrate solutions in hydrogen peroxide at different temperatures. One milliliter of pink cobalt(II) chloride catalyst solution is added to three of the vials.

The vial on the right is initially at 55°C. When the pink cobalt(II) chloride catalyst is added, the solution turns green and bubbles form, and some of the solution foams out of the vial. The color change is indicative of an intermediate chemical species of cobalt.

The second vial from the right was initially at 35°C. When the catalyst is added to this solution, the reaction proceeds more slowly than in the solution on the right. The role of the cobalt is to serve as a catalyst. Hydrogen peroxide oxidizes the cobalt(II) to cobalt(III). The cobalt(III) intermediate subsequently oxidizes the tartrate to carbon dioxide gas, and returns to the original cobalt(II).

The next vial is at room temperature, so the catalyzed reaction proceeds even more slowly. It takes over an hour for this reaction to reach completion.

The control vial on the left was initially at 55°C. The absence of bubbles in the control solution indicates that even at this elevated temperature, without a catalyst, no reaction occurs between the peroxide and the tartrate.

Discussion

A catalyst alters the rate of a chemical reaction without itself being consumed. An intermediate is formed during one step of a chemical reaction and consumed in a later step, so that, like the catalyst, it does not appear in the net equation for a reaction. The intermediate in this reaction is a cobalt(III)-tartrate complex, [Co(C4H4O6)3)]3-.

The overall reaction taking place is

C4H2O64-(aq) + 5 H2O2(aq) → 4 CO2(g) + 4 OH-(aq) + 4 H2O(l)

Keywords

Catalysis | Kinetics

These ChemEd DL Resource Groups Include This Video

Rates of Reactions
Reactions in Aqueous Solutions
Acid Base Reactions


Embedding Video in Learning Materials

The ChemEd DL encourages you to include this high-quality video in learning materials you create. We provide means to embed the video in a Web page, in a wiki, or in an online course using a course-management system. (If you want to include the video in another kind of learning material, contact us.)

If you create learning materials and make them available through the ChemEd DL, all of our videos may be freely used. For example, you can embed any video into the ChemPRIME wiki, or an online course on the ChemEd Moodle Courses site. For more information about developing resources at ChemEd DL, click here.

Allowed Uses

This video is owned by the Journal of Chemical Education and copyrighted by the ACS Division of Chemical Education, Inc. All rights reserved. To use the video in your materials at your own institution, you must be a subscriber to JCE Web Software. Subscribe as an individual or an institution at the JCE Online Store.

Individual subscribers are permitted to incorporate video into PowerPoint or other multimedia presentations or into lessons written in HTML, provided the presentations or lessons are restricted to the subscriber’s own class (lecture presentation or course management system where only enrolled students have access). Through an institutional subscription the video becomes available for viewing by any student using a computer within the institution’s range of IP addresses. A student could also incorporate video into a report or presentation and the video would play from computers at the student’s own institution.

Attribution

When this video is incorporated into other materials, this attribution should be present: Video from JCE Web Software, Chemistry Comes Alive!. Copyright ACS Division of Chemical Education, Inc. Used with permission.

WebPage/Iframe

In the box below is HTML code to embed this video into your own Web page. Copy the code and paste it into your Web page code.

ChemPRIME/MediaWiki

ChemPRIME project is a full general chemistry textbook available online through the ChemEd DL. We seek collaborators to add exemplars to ChemPRIME that describe chemistry topics within various contexts, such as biological science, food chemistry, and everyday life. ChemPRIME is built using MediaWiki (the same platform used to build Wikipedia). ChemEd DL encourages users to add ChemEd DL videos to their own exemplars. MediaWiki does not allow full HTML code to be inserted, so the ChemEd DL community has created a MediaWiki extension that enables embedding videos. The extension is installed in ChemPRIME, so the code below allows you to add this video to a ChemPRIME page. More information is at ChemPRIME Help:Media. Contact us if you would like to use this MediaWiki extension on your own wiki.

ChemEd Courses/Moodle

ChemEd Courses is the ChemEd DL's Moodle course management system. Users can manage their own courses, or develop learning resources in Moodle to share with the community. Moodle does not allow full HTML code to be inserted, so the ChemEd DL community has created a Moodle extension that enables embedding videos. The extension is installed in ChemEd Courses, so the code below allows you to add this video to a course in ChemEd Courses. If you would like to use this Moodle extension within your own Moodle installation, contact us.

ChemPaths/Drupal

ChemPaths is the ChemEd DL's Drupal-powered integrated online textbook. Students can explore a full online textbook or other learning pathways. Instructors can sign-up to build their own pathways through course material. Drupal does not allow full HTML code to be inserted, so the ChemEd DL community has created a Drupal extension that enables embedding videos. The extension is installed in ChemPaths (currently in beta-testing), so the code below allows you to add this video to a course in a pathway. If you would like to use this Drupal extension within your own Drupal installation, contact us.

 Access to this video is restricted to JCE Web Software subscribers. To subscribe, either as an individual or an institution, visit the JCE Online Store.