Question

Which of the following is a synthesis reaction? AgNO3 + NaCl → AgCl + NaNO3 BaO + H2O → Ba(OH)2 SO3 + H2O → H2SO4 Cu + AgNO3 → Ag + CuNO3

Answer 1

Answer : The synthesis reaction are,

$BaO+H_2O\rightarrow Ba(OH)_2$

$SO_3+H_2O\rightarrow H_2SO_4$

Explanation :

Synthesis reaction : It is a type of combination reaction where the two or more  reactants combine to form a single product. In this reaction, reactant may be an element or compound and product is always compound.

From the given reactions, we conclude that

$BaO+H_2O\rightarrow Ba(OH)_2$

$SO_3+H_2O\rightarrow H_2SO_4$

These two reactions are the example of synthesis reaction.

While,

$AgNO_3+NaCl\rightarrow AgCl+NaNO_3$ is a double displacement reaction in which the cation and anion of two different reactants exchange their places to give two different products.

And,

$Cu+AgNO_3\rightarrow Ag+CuNO_3$ is a single replacement reaction in which the most reactive metal displaces the least reactive metal form its solution.

Answer 2

SO3 + H2O → H2SO4 if im not mistaking