Question

Classify each reactant and product in this reaction as an acid or base according to the Brønsted theory.

HF + H2O = F + H30+


Answer Bank
HF
H30+
F-
H2O

Answer 1

Reaction:
`\rm HF + H_2O \rightleftharpoons F^(-) + H_3O^(+)`.

• 
  `\rm HF`: Bronsted-Lowry Acid.
• 
  `\rm H_3O^(+)`: Bronsted-Lowry conjugate Acid of
• 
  `\rm F^(-)`: Bronsted-Lowry conjugate Base of
  `\rm HF`.
• 
  `\rm H_2O`: Bronsted-Lowry Base.

Step-by-step explanation:

In the Bronsted-Lowry acid-base theory, the acid in a reaction is the species that loses a proton,
`\rm H^(+)`. The resultant species would be the conjugate base of that acid.

On the other hand, the Bronsted-Lowry base in a reaction is the species that accepts a proton
`\rm H^(+)`. The resultant species would be the conjugate acid of that base.

Identify the conjugate acid-base pairs in this reaction. Note that the two species in each pair are related by the gain or loss of a single proton. Therefore, their formula should look similar to each other.

For this reaction,
`\rm HF` and
`\rm F^(-)`, as well as
`\rm H_2O` and
`\rm H_3O^(+)` form two similar-looking reactant-product pairs:

• The reactant
  `\rm HF` loses one proton to form the product
  `\rm F^(-)`. Therefore,
  `\rm HF\!` would be the Bronsted-Lowry acid, while
  `\rm F^(-)\!` would be its conjugate base.

• The reactant
  `\rm H_2O` gains one proton to form the product
  `\rm H_3O^(+)`. Therefore,
  `\rm H_2O\!` would be the Bronsted-Lowry base, while
  `\rm H_3O^(+)\!` would be the conjugate acid.