Write complete and balanced equatons for each of the following reactions:

(1) P₂O₅ + H₂O --->

(2) NaCl + AgNO₃ --->

(3) H₂SO₄ + NaOH (limited)

(4) FeCl₂ + AgNO₃ --->

There are four train lines between X and Y; and three train lines between Y and Z. Find the number of ways a person can travel:

(1) by train from X to Z by way of Y

(2) roundtrip by train from X to Z by way of Y

How many ways can the roundtrip by train be taken from X to Z by way of Y, given that you do not use the same train line more than once?

Sketch and name all the possible linkage and stereoisomers of the following coordination compunds:

(a) [Pt(NH₃)₂(SCN)₂]

(b) [Co(en)(H₂NCH₂CO₂)₂]CI