Charge is applied to a circular disk of ebonite of radius by rubbing it while it is rotating. in
this way the surface charge density becomes proportional to the radial distance from the
center. show that the electric field strength on the axis of the disk at an axial distance ℎ from
the center is
√
−
√ .

I dont get the question need more info sorry.

The molecules contain like 54 of water 

The activity series is shown in the attached picture. if the element is below the other, then you can displace the other. following the activity series as a guide, the reactions are as follows: nickel and aluminum chloride3 ni + 2 alcl₃  → 3 nicl₂ + 2 albarium and copper bromideba + cubr  →  no reaction because cu is less oxidizable than bapotassium nitrate and aluminum3 kno₃ + al  → al(no₃)₃ + 3 ksodium phosphate and zincnaso₄ + zn  → znso₄ + na