Answer:
Synthesis Reaction
Step-by-step explanation:
Here we see H2 and O2 are being combined H2O. Synthesis reactions are where we see a combination to make a single product.
So here it'd be A + B =AB
2Na(s)+Cl2(g)→2NaCl(s)
Decomposition would be the break down of a compound into 2, the opposite of synthesis.
AB = A + B
2HgO(s)→2Hg(l)+O2(g)
Single replacement is where 1 element replaces another in a reaction, or switches place with 1 element.
AY + B = A + BY
2 HCl(aq) + Zn(s) → ZnCl2(aq) + H2(g)
Double replacement is similar but 2 elements are switch/replaced.
AY + BX = AX + BY
CuCl2(aq) + 2 AgNO3(aq) → Cu(NO3)2(aq) + 2 AgCl(s)