For the following reaction, label each of the below species as an acid or a base. Use lower case letters only (e. g. acid)
HCN + HPO4⁻² ⇔ H2PO4⁻ + CN⁻
Will the above reaction take place spontaneously? (Is the reaction product-favored? Does the equilibrium lie to the right?)

Explanation:

According to Arrhenius, bases are the species which dissociate to give hydroxide ions, that is, .  

For example,

Arrhenius acids are the species which dissociate to give hydrogen ions, that is, .

For example,

In the given example, HCN is donating the hydrogen ion therefore, it is an acid whereas is accepting the hydrogen ions so it acts as a base.

Now, standard values of the given species are as follows.

 HCN = 124.7 kJ/mol,       = -1089.3 kJ/mol

  = -1130.4 kJ/mol,       = 172.4 kJ/mol

Therefore, of the given reaction will be calculated as follows.

                   = [-1130.4 + 172.4] - [124.7 + (-1089.3)]

                   = (-958 + 964.6) kJ/mol

                   = 6.6 kJ/mol

Since, is greater than zero. Hence, the reaction will be non-spontaneous.

10 years is the answer