Reaction between an acid and a base to show the process of neutralization

  Materials Required

Dilute hydrochloric acid, dilute sodium hydroxide solution, phenolphthalein indicator, test tubes, dropper, test-tube stand.

  Procedure

Real Lab Procedure

  • Take about 5 mL of dilute hydrochloric acid in a test tube.
  • Add 1-2 drops of phenolphthalein indicator to the solution and note down if any change in colour.
  • Take about 10 mL of dilute sodium hydroxide solution in another test tube.
  • Take out sodium hydroxide solution with the help of a dropper and start adding this solution dropwise into the test tube containing hydrochloric acid till a change in colour is observed
  • What colour do you get?
  • With the help of another dropper, take out hydrochloric acid and start adding it dropwise into the coloured solution obtained above.
  • Note your observation

Simulator Procedure:

  • Click the Cap of Hydrochloric acid to open the glass bottle.
  • Drag the bottle into the measuring Cylinder.
  • Drop the bottle to pour 5ml of solution into the measuring cylinder.
  • Drag and drop the measuring cylinder containing 5ml Hydrochloric solution to the Test-tube A.
  • Drag the dropper to add 1 to 2 drops of phenolphthalein into the test-tube A.
  • Click the cap of Sodium Hydroxide to open the glass bottle.
  • Drag the bottle into the measuring cylinder.
  • Drop the bottle to pour 10ml of solution into the measuring cylinder.
  • Drag and drop the measuring cylinder into the test tube B and pour 10ml solution.
  • Drag and drop the dropper to test tube B.
  • Drag the Dropper to test tube A containing the mixture of Hydrochloric acid and phenolphthalein.
  • Drop the dropper to add the solution dropwise to test tube A.
  • Show a colour change solution to Pink.
  • Click the Cap of Hydrochloric acid to open the glass bottle.
  • Drag the bottle into the measuring Cylinder.
  • Drop the bottle to pour 5ml of solution into the measuring cylinder.
  • Drag and drop the measuring cylinder containing 5ml Hydrochloric solution to the Test-tube A.

Observation

  • Colour of the hydrochloric acid solution does not change on addition of phenolphthalein indicator.
  • On adding nearly 5 mL sodium hydroxide solution to the mixture of hydrochloric acid and phenolphthalein solution, the colour of the mixture changes to pink.
  • On addition of hydrochloric acid solution to the pink solution, the colour starts fading gradually and finally the solution becomes colourless.

Conclusion

  • Phenolphthalein indicator remains colourless in the acidic solution while its colour changes to pink in basic solution.
  • It is found that on adding a base in an acid, a stage reaches when effect of acid is neutralised by base and vice-versa as indicated by colour changes of indicator.

Precautions

Be careful while handing the acid carefully.