Conversion of a Carbonate to a Chloride

(revised 4 June 2024)

Introduction

The laws of conservation of matter and definite proportions are now accepted as basic principles of chemistry. These laws are fundamental to the writing of chemical equations, and, thus, to the information equations contain. In this experiment, sodium chloride will be made from sodium carbonate by the following equation:

sodium carbonate + hydrochloric acid right arrow sodium chloride + water + carbon dioxide

Knowing your starting number of moles of sodium carbonate and using the above equation you can predict the mass of NaCl that theoretically can be made and recovered, and, hence, calculate a percentage yield. Since different students will start with different amounts of sodium carbonate and hydrochloric acid a comparison of the data from several students can serve to demonstrate the law of definite proportions. In this case, if the percentage yield is very similar, that same product most likely is the same.

Prelab

Provide the balanced equation for this reaction, using the chemical formulas of the compounds. Provide the physical state of each reactant and product in the equation, e.g. gas (g), liquid (l), solid (s), or aqueous solution (aq).
Calculate the amount of concentrated hydrochloric acid, 12.0 M, required to react with the 0.300 g sodium carbonate. Assuming 20 drops per mL, how many drops are required?
Using 0.300 g of sodium carbonate, calculate the theoretical yield and the theoretical volume of the gaseous product formed in this reaction?
Do some research to provide two (2) uses in the home or industry for sodium carbonate.

Safety

Wear safety glasses. Cold materials look very similar to hot ones. Think before you touch something. Use tongs or protective gloves to handle hot equipment. Be very careful when handling concentrated hydrochloric acid, because it will cause serious burns. Do not splatter or spill it. One drop can cause damage!

Procedure

Weigh accurately a crucible and cover. Now clean the crucible and its cover by heating strongly for several minutes. Let cool to room temperature and reweigh. Are weights the same? Add about 0.300 g of sodium carbonate to the crucible. To do this, weigh the container containing the entire amount of sodium carbonate. Place an amount of sodium carbonate in the crucible and reweigh the container containing the sodium carbonate once again. The difference in the weights of the container is the weight of sodium carbonate placed into the crucible. This weighting technique is called weighing by difference.

Add the 12.0 M hydrochloric acid dropwise to the sodium carbonate. Why does it fizz? Continue adding until you reach your calculated amount. If it is still fizzing, keep adding until it stops. Once the fizzing has stopped, add 5 more drops. Swirl the crucible to mix the reagents but do not use a stirring rod. Place the crucible on a clay triangle with the lid ajar and warm gently with a Bunsen burner to evaporate the liquid. If it splatters you will have to start over. When the liquid has evaporated, cover the crucible completely and heat strongly for 5 minutes. Allow to cool to room temperature and weigh accurately. Repeat the experiment with another sample of sodium carbonate.