1) how many structures are possible for a square planar molecule with a formula of ax2y2?
2)how many structures are possible for a tetrahedral molecule with a formula of ahxyz?

1) Two structures are possible with the molecular formula having square planar geometry.

2) Only one structure is possible for the formula having tetrahederal geometry.

Explanation: For both the cases, we are fixing the position of A-atom which is the central metal atom.

1) When A is fixed and we are ought to surround 2 X and 2 Y-atoms around it. There are 2 possible ways in which can be done.

When both the X-atoms are adjacent to each other, it is known as cis-conformation.

When both the X-atoms are anti to each other, it is known as trans-confirmation.

2) When A is fixed and four different groups are surrounding this atom, only 1 structure is possible which have a tetrahederal geometry.

The structure are shown in the given image below.

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.