 In the reaction of sodium hydrogen carbonate with hydrochloric acid, you will mass a 100 milliliter beaker. You will then add about 2 grams of sodium hydrogen carbonate to the beaker. You will remass the beaker and the sodium hydrogen carbonate to give you the mass of the sodium hydrogen carbonate. Add about 5 milliliters of water to the beaker. This will help to dissolve the sodium hydrogen carbonate. Slowly swirl the beaker to get some or all of the sodium hydrogen carbonate in solution. We will add a couple of drops of Bromthymol blue indicator to the solution. Bromthymol blue is an acid-base indicator, is blue and basic solution, and yellow and acidic solution. We will cover the beaker with a watch glass to minimize loss of compound due to splattering. You will slowly add 3 molar hydrochloric acid to the sodium hydrogen carbonate. The sodium hydrogen carbonate and the hydrochloric acid react to produce sodium chloride, carbon dioxide gas, and water. The carbon dioxide is released from the solution, which is the fizzing that we see. The water joins the water that's already in the solution, and the sodium chloride that's produced dissolves in the water. We can tell when we've added an excess of hydrochloric acid, when the solution turns yellow, all the sodium hydrogen carbonate dissolves and no more carbon dioxide gas is emitted. We take a little water and rinse off the bottom of the watch glass, and we rinse down the side to the beaker to make sure that all the sodium hydrogen carbonate has had a chance to react. You will evaporate the water to leave the sodium chloride. You will mass the beaker and the sodium chloride to determine the mass of the sodium chloride.