Question

An element which can exist as a positive ion in acidic solution and also as a negative ion in basic solution is said to be:
A: Colloidal
B: Hypertonic
C: Hypotonic
D: Amphoteric

Answer 1

Hint: ${H^ + }$ ions are present in acidic solution and $O{H^ - }$ ions are present in basic solution. If an element can exist as both positive ions in acidic medium and basic ion in negative medium then this means that the element can react with both acids and bases.

Complete step by step answer:
In this question we have to find those elements which exist as both positive ions in acidic solutions and negative ions in basic solutions.
Colloidal solution is the solution in which microscopic particles are dispersed evenly into other material. This doesn’t exist as positive ion in acidic medium and negative ion in basic medium as it is not a chemical compound. This means this is not our answer.
Hypertonic solution is the solution which contains higher concentration of solute as compared to the other solution. This term is used while comparing a solution with the other. This is not our answer as it is also not a chemical compound.
Hypotonic solution is a solution which contains less amount of solute as compared to the other solution. This term is also used while comparing two solutions. If one solution is hypotonic then the other is hypotonic. This means it is also not the answer as it is not any chemical compound.
Amphoteric compounds are the compounds which can react with both acids as well as bases. In this question we had to find the elements which can exist as positive ions in acidic solution and negative ions in basic solution. As these elements can exist in both acidic and basic mediums then these substances can react with both acids and bases. Amphoteric is the term which is used for the elements which can react with both acids as well as bases.
This means the correct answer is option D that is amphoteric.

Note:
 Oxides and hydroxides of aluminium, zinc, copper, tin, lead and beryllium are amphoteric in nature. This means oxides and hydroxides of these elements can react with acids and bases. Sulphuric acid is also an example of amphoteric compounds.