alkanoic acid with metal

Reaction of Mg with methanoic acid :
Mg(s) + 2HCOOH(aq) → (HCOO)2Mg(aq) + H2(g)

Reaction of Mg with ethanoic acid :
Mg(s) + 2CH3COOH(aq) → (CH3COO)2Mg(aq) + H2(g)

Reaction of Mg with propanoic acid :
Mg(s) + 2CH3CH2COOH(aq) → (CH3CH2COO)2Mg(aq) + H2(g)

===========
In writing the required equations, two points must be noticed:

Firstly, the symbol for a reversible reaction is “→” but not “=”. “→” is read as “change to”. The symbol “=” is used in very old chemistry books, and is also used in Yahoo to represent the equilibrium sign (double arrows) because we cannot type the sign in Yahoo.

Secondly, the formula of a magnesium alkanoate should be written as (RCOO)2Mg instead of Mg(RCOO)2. Stictly speaker, Mg(RCOO)2 is incorrect. For acids like HCl, H is written before Cl. When Mg2+ replaces the H+ of the acid, Mg should take the position of H, i.e. MgCl2. For alkanoic acid RCOOH, H is written at the end. When Mg2+ replaces the H+ of the acid, Mg should take the position of H, i.e. (RCOO)2Mg.

With methanoic acid:
Mg + 2HCOOH = Mg(HCOO)2 + H2
With Ethanoic acid:
Mg + 2CH3COOH = Mg(CH3COO)2 + H2
With Propanoic acid:
Mg + 2CH3CH2COOH = Mg(CH3CH2COO)2 + H2