Which of the following compounds will form [tex][tex]$CO_2$[/tex][/tex] and [tex][tex]$H_2O$[/tex][/tex] when it reacts with an acid?

A. [tex][tex]$Mg(OH)_2$[/tex][/tex]
B. [tex][tex]$NH_3$[/tex][/tex]
C. [tex][tex]$NaC_2H_3O_2$[/tex][/tex]
D. [tex][tex]$CaCO_3$[/tex][/tex]



Answer :

To determine which compound will form [tex]\( CO_2 \)[/tex] and [tex]\( H_2O \)[/tex] when it reacts with an acid, we need to consider the chemical reactions involved for each compound.

Let's analyze the reactions:

1. [tex]\( Mg(OH)_2 \)[/tex] (magnesium hydroxide):
- When [tex]\( Mg(OH)_2 \)[/tex] reacts with an acid (e.g., HCl), the reaction is:
[tex]\[ Mg(OH)_2 + 2HCl \rightarrow MgCl_2 + 2H_2O \][/tex]
- This reaction produces [tex]\( MgCl_2 \)[/tex] and [tex]\( H_2O \)[/tex], but no [tex]\( CO_2 \)[/tex].

2. [tex]\( NH_3 \)[/tex] (ammonia):
- When [tex]\( NH_3 \)[/tex] reacts with an acid (e.g., HCl), the reaction is:
[tex]\[ NH_3 + HCl \rightarrow NH_4Cl \][/tex]
- This reaction produces [tex]\( NH_4Cl \)[/tex], but neither [tex]\( H_2O \)[/tex] nor [tex]\( CO_2 \)[/tex].

3. [tex]\( NaC_2H_3O_2 \)[/tex] (sodium acetate):
- When [tex]\( NaC_2H_3O_2 \)[/tex] reacts with an acid (e.g., HCl), the reaction is:
[tex]\[ NaC_2H_3O_2 + HCl \rightarrow NaCl + HC_2H_3O_2 \][/tex]
- This reaction produces sodium chloride ([tex]\( NaCl \)[/tex]) and acetic acid ([tex]\( HC_2H_3O_2 \)[/tex]), but neither [tex]\( H_2O \)[/tex] nor [tex]\( CO_2 \)[/tex].

4. [tex]\( CaCO_3 \)[/tex] (calcium carbonate):
- When [tex]\( CaCO_3 \)[/tex] reacts with an acid (e.g., HCl), it undergoes the following reaction:
[tex]\[ CaCO_3 + 2HCl \rightarrow CaCl_2 + H_2O + CO_2 \][/tex]
- This reaction produces calcium chloride ([tex]\( CaCl_2 \)[/tex]), water ([tex]\( H_2O \)[/tex]), and carbon dioxide ([tex]\( CO_2 \)[/tex]).

Given the reactions above, the only compound that forms both [tex]\( CO_2 \)[/tex] and [tex]\( H_2O \)[/tex] when it reacts with an acid is [tex]\( CaCO_3 \)[/tex].

Therefore, the correct answer is [tex]\( \boxed{4} \)[/tex].