Problem: H2PO4– is the conjugate _____ of H3PO4 and the conjugate _____ of HPO42–.A. acid / acidB. acid / baseC. base / acidD. base / base

FREE Expert Solution

Recall that the conjugate acid of a base is simply the compound formed when a base gains a hydronium ion (H+). It's considered as an acid because it can lose H+ to reform the base. 

On the other hand, the conjugate base of an acid is simply the compound formed when an acid loses a hydronium ion (H+). It's considered as a base because it can gain H+ to reform the acid.


Phosphoric acid (H3PO4) is a weak triprotic acid, meaning it can donate three protons (H+and it will have three equilibrium reactions.

Removing one H+ per step in H3PO4:


81% (405 ratings)
View Complete Written Solution
Problem Details

H2PO4 is the conjugate _____ of H3PO4 and the conjugate _____ of HPO42–.

A. acid / acid
B. acid / base
C. base / acid
D. base / base

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Conjugate Acids and Bases concept. If you need more Conjugate Acids and Bases practice, you can also practice Conjugate Acids and Bases practice problems.