Acids and Bases

 

Acid-Base Titration – Add NaOH (aq) to a solution of HCl and phenolphthalein.

Acid Rain – Add a small piece of blackboard chalk (CaCO3) to 6 M HCl (aq) to show a more vigorous acid-base reaction.

Acids and Bases – Add drops of 0.1 M NaOH to a magnetically stirred solution of water and universal indicator until it turns blue, then add drops of 0.1 M HCl until the solution turns orange.

Amphoteric Hydroxides – Add NaOH to samples of Al(NO3)3 and Fe(NO3)3 to form insoluble metal hydroxides, then add HNO3 and more NaOH to different samples of each to identify which metal hydroxides are amphoteric.

Buffer Demo – Observe the effects of adding 6 M HCl (aq) to H2O, 0.1 M and 1 M CH3COOH/NaCH3COO buffer in the presence of an indicator.

Buffer vs Acid – Simultaneously add 1 M acetic acid and 1 M acetic acid/sodium acetate to graduated cylinders containing CaCO3, and observe the relative rates of reaction.

Conductivity Tester Demos

  • Acetic Acid and Ammonia – Use the conductivity tester to show that CH3COOH and NH3 are weak electrolytes. Have students predict the results of mixing equal amounts of NH(aq) and CH3COOH (aq), then test the conductivity of the mixture – does it still conduct electricity? Does the bulb glow dimly or brightly? Why?
  • Glacial Acetic Acid – Test the conductivity of glacial acetic acid, then add water gradually to see how the conductivity changes.
  • HCl and NaOH – Use the conductivity tester to show that HCl and NaOH conduct but H2O does not. Add Yamada Universal Indicator to show that HCl is an acid, NaOH is a base, and H2O is neutral. Finally mix equal amounts of HCl and NaOH to produce a neutral solution – will it still conduct electricity?

Electrolytic Titration of Ba(OH)2 – Add H2SO4 gradually to Ba(OH)2 (aq) in which the conductivity tester is immersed; the light bulb gradually dims as the endpoint is reached because the products are H2O and insoluble BaSO4.

Hydrolysis of Salts – Dissolve various salts in water containing Yamada indicator to demonstrate their acidity or alkalinity in solution.

Milk of Magnesia Demo – Add HCl gradually to Milk of Magnesia in a beaker (an aqueous suspension of Mg(OH)2) to show the dissolution of Mg(OH)2 as the pH decreases.

Zinc and HCl– Add ZnO to water to show that it does not dissolve appreciably, then add acid to show that a basic oxide reacts with (and therefore dissolves in) an acid