Question

Carrie is performing an experiment on acids and bases, so she forms the following hypothesis: If an acidic solution is added to a basic solution, the pH of the resultant solution will decrease. What is the dependent variable in Carrie's experiment?

Answer 1

if strong acid react with strong base then the salt Will be neutral or its pH will be near 7.

and if acid is strong and base is weak,then the salt Will be acidic and it's pH will be less than 7,

and if base is strong and acid is weak,then the salt formed will be basic.

now come to your question,

you are saying that if acid is added to base then the resultant solution will be acidic( it's pH will be decreased). it means that the acid used here is strong and base is weak.

now it depends on two factor

concentration of H+ ions and OH- ions.

if the concentration of H+ is more then it is acid,

if the concentration of OH- ions is more then it is basic