In this experiment we will analyze a sample of sodium bicarbonate to find the percentage loss in weight when it is decomposed by heat. To do this, we will heat a known weight of sodium bicarbonate and weigh the sodium carbonate residue.

**Procedure**

- Weigh a clean, dry crucible to the nearest milligram. Add about 4 or 5 grams of sodium bicarbonate and re-weigh. Support the crucible in a clay triangle mounted on a ring and stand.
- Heat the crucible in a small Bunsen flame for 2 or 3 minutes, then gradually raise the flame over a period of 5 minutes until the lower third of the crucible is dull red in color. Turn off the burner, allow the crucible to cool, and weigh it.
- To make certain that the decomposition is complete, re-heat the crucible with the hottest flame of the burner for about 5 minutes. Then allow the crucible to cool and re-weigh it. This weight should be within a centigram or two of the weight after the first heating. Use the smaller of the two masses in your computations.
- Compute (a) the weight of sodium bicarbonate used, and (b) the loss in weight.
- Now calculate the percentage loss in weight.

- Write the equation for the reaction taking place in the crucible.
- Calculate the percentage loss in weight from the equation.
- Compute your percentage error.
- How do you account for this error?
- Calculate the weight of (a) water and (b) carbon dioxide evolved during the reaction.