Question

Which of the following is a single replacement reaction?Fe2O3 + 3H2O yields 2Fe(OH)3

Answer 1

Mg + 2HCl yields MgCl2 + H2 since chlorine is being displaced

Answer 2

Answer: $Mg+2HCl\rightarrow MgCl_2+H_2$

Explanation:

1. Synthesis reaction is a chemical reaction in which two reactants are combining to form one product.

Example: $Fe_2O_3+3H_2O\rightarrow 2Fe(OH)_3$  

$2Mg+O_2\rightarrow 2MgO$

2. Double displacement reaction is one in which exchange of ions take place.  

Example: $FeS+2HCl\rightarrow FeCl_2+H_2S$

3. Single replacement reaction is a chemical reaction in which more reactive element displaces the less reactive element from its salt solution.

Example: $Mg+2HCl\rightarrow MgCl_2+H_2$