Question

Please solve these questions, I try a lot to answer all of them but I couldn’t answer it.

Thanks in advance.

 

Propanoic acid (C₂H₅COOH) is described as a weak acid. Define the term weak acid.

 

Write a balanced chemical equation to show the dissociation of propanoic acid (C₂H₅COOH). Physical states must be included.

 

A solution of propanoic acid and sodium propanoate (C₂H₅COONa) behaves as a buffer. Describe the term buffer solution. No chemical equations are needed.

 

Write a balanced chemical equation to show the dissociation of sodium propanoate (C₂H₅COONa). Physical states must be included.

 

Explain how a solution containing propanoic acid and sodium propanoate can function as a buffer solution. Your answer must include balanced chemical equations, physical states included.

Answer 1

Carboxylic acids are weak acids because they only partially ionise in solution. Their solutions do not contain many hydrogen ions compared to a solution of a strong acid at the same concentration. In a solution of strong acid, the molecules are fully ionised. In a weak acid, few of the molecules are ionised.

CH3CH2COOH + H2O <--> CH3CH2OO− + H3O+

Because propanoic acid is weak -- and therefore does not completely dissociate in water -- the formula is written with a forward/ reverse arrow to indicate that there is no particular favour of the products in equilibrium.

A buffer solution is a solution that only changes slightly when an acid or a base is added to it. For an acid-buffer solution, it consists of a week acid and its conjugate base. The added acid or base is neutralized.

C2H5COONa =C2H5COO^- + Na^+

Basically the first make is given by saying that C2H5COOH dissociates into C2H5COO- and H+ from which the H+ ion reacts with an OH- ion when present producing H2O and keeping the pH of the solution the same.