Which of the following is not suitable for testing the presence of an acid?
A) adding aqueous potassium carbonate.
B) adding aqueous potassium hydroxide.
C) adding Universal Indicator.
D) adding zinc powder.
Personally, I feel that all of them are suitable.
And I can understand why you think all of them are suitable; however, how would you know by adding aq KOH that a reaction had occurred? A would fizz due to CO2 gas, C would change color, D would fizz due to H2 gas. B would react but how would you know it?
Note: IF the acid were concentrated (very concd) and IF the KOH were concentrated (very concd), then you would be able to tell because the neutralization generates heat.