Objective
- To identify baking soda among given samples of chemicals
Materials required:
- Samples: sodium carbonate, sodium hydrogencarbonate, ammonium chloride, sodium chloride etc.
- red litmus paper
- lime water
- dil. hydrochloric acid
- test tubes
Procedure:
- Take ~ 1 g each of the four given samples separately in four test tubes and label them as A, B, C, and D
- Add about 5 mL water in each and shake well
- Put a drop of every salt’s solution on separate red litmus paper strips
- Add 1 mL of dil. hydrochloric acid in each test tube and check for effervescence If yes, perform the lime water test as detailed below.
- Set up the apparatus (test tube with cork and tube)
- Add dil. hydrochloric acid drop by drop to the solution
- Pass the liberated gas evolved through the lime water in a test tube
Findings:
- One of the sales turns blue litmus red and the gas turns lime water milky
Conclusions:
- Sample which turned red litmus blue and lime water milky contains baking powder
Theory:
- Washing soda (Na2CO3.10H2O) and baking soda (mainly NaHCO3) are white solids. Their aqueous solutions are alkaline and turn red litmus blue. Carbonates and hydrogencarbonates react with dilute acids and produce carbon dioxide gas which turns lime water milky.