The compound, sodium hydrogen carbonate may be decomposed by heating. There are three very plausible sets of products that may be written to show the reaction. They are as follows:

1. Sodium hydrogen carbonate (solid) <----> sodium hydroxide (solid) + carbon dioxide (gas)

2. Sodium hydrogen carbonate (solid) <----> sodium oxide (solid) + carbon dioxide (gas) + water (gas)

3. Sodium hydrogen carbonate (solid) <----> sodium carbonate (solid) + carbon dioxide (gas) + water (gas)

The purpose of this experiment is for you to experimentally determine which of these three equations correctly represents the decomposition. You will need to show on what basis you eliminated two of the reactions and kept just the one. Rather than just relying on one test, you will carry out two procedures, one in which you will consider the mass of the solid product, and the other where you will measure the amount of gaseous product(s) given off.

You will need to use stoichiometry to calculate for each equation (1) the amount of the solid product that would result from heating 2.00 g of the sodium hydrogen carbonate and (2) the amount of the sodium hydrogen carbonate that you would need to use to produce 50.00 mL of carbon dioxide at STP. You will use the Ideal Gas Equation to adjust this amount for the actual room conditions the day of the experiment.

Part 1. Design a quick test to determine if you can possibly eliminate equation 1 and focus on the other two equations, or eliminate equations 2 and 3 and concentrate on equation 1.

Part 2. Carefully measure the 2.00 g of sodium hydrogen carbonate into a crucible in the same manner you used in Exp. 3. It might be a good idea to review the techniques for using crucibles that is on the website. Review use of crucibles

Heat the contents of the crucible for about 10 minutes. You may carefully lift the lid off the crucible and break up any "clumps" that might form during this time.

You will want to heat the crucible and contents as you did in Exp. 3 until a constant mass is obtained. Why? The mass of the contents should be a good indication of which of the three equations is correct.

Part 3. Weigh out the amount of sodium hydrogen carbonate needed to produce 50.00 mL of carbon dioxide according to the equation you have decided on from Part 2. See Figure 1 for how you are to assemble the equipment. Heat until no more bubbles are seen. Remove the tubing from the eudiometer BEFORE you turn off the Bunsen burner.

Note:You will need to make a salt water solution to put in the trough and eudiometer rather than using tap water. This is because carbon dioxide is somewhat soluble in distilled and tap water, but quite insoluble in salty water.

Identify which of the three equations you have determined to be the correct representation of what happens when you heat sodium hydrogen carbonate. Tell why, giving all of the supporting data, you selected the one you did, and why you rejected the other two. Assuming you did not get 100% yield for Parts 2 and 3, discuss where in your procedure error could have been introduced. Be specific. Do Not simply say "experimental error" or "human error".