Hand warmers work because of a rusting process. The rusting is a redox reaction and the equation is as follows: 4Fe(s) + 3O2
(g) -> 2Fe2
(s) In today’s lab we will explore how the rusting process is used in hand warmers.
1) Place an opened Ziploc bag into a beaker and fold the edges over the side of the beaker so that you will be able to pour reactants into it without it falling over.
2) Add the following reactants to the Ziploc bag:
12-13g Iron Powder
Note: Be careful about spills. To save time, use three different beakers as your measuring containers (or better yet, 2 beakers and one piece of weigh paper for the NaCl). Make sure you measure the mass of the empty beakers and weigh paper.
3) Close the bag and shake GENTLY to mix the reactants thoroughly.
4) Add 3mL of water to the bag, quickly squeeze out all air, and seal it. There should be a minimal amount of air in the bag. Your heat warmer is now ready to be activated.
5) To activate, open the bag and let some air come in. Gently knead the mix together and feel for any heat transfer.
1) Is this an endothermic or exothermic reaction? How do you know?
2) Why is it necessary to open the hand-warmer bag to start the reaction? (Hint: Look at the reaction equation!)
3) Try removing all of the air and closing the bag again. Wait a few minutes. What effect does this have on the temperature of the bag? Why?
4) In this reaction, electrons are transferred from the Fe to the O. Keeping this in mind, why do you think you added salt to the mixture even though it is not a part of the reaction?