identify what kind of reaction each of the following is:
a. X + Y - XY
b. + XY - X + Y
c. AB + XY - AY + XB
d. AB + X - AX + B
e. AB + CD - AD + BC
f. Acid + base - salt + water

1) X + Y $\to$XY = It is a combination reaction
2) XY $\to$X + Y = It is a decomposition reaction
3) AB + XY $\to$AY + XB = It is a double displacement reaction.
4) AB + X $\to$AX + B = It is a displacement reaction
5) AB + CD $\to$AD + BC = It is a double displacement reaction. 
6) Acid + Base $\to$Salt + water = It is a neutralisation reaction