Of the two bottles, one contains HCl solution and the other a buffer solution. Each of the bottles is labelled as pH=5. how can you identify the solutions?

Explanation

if pH of the solution is measured after adding equal drops of NaOH solution to each of the solution, it will be found that pH has increased markedly for one solution, while it remains almost the same for the other solution. The solution for which pH remains almost the same is a buffer solution annd the solution for which pH increases is a solution of HCl.