A cannon on a level plain is aimed 50 degrees above the horizontal and a shell is fired with a muzzle velocity of 1000m/s toward a vertical cliff 3214 metre away. How far above the bottom does the shell strike the side wall of the cliff. My answer is 4875m but I don't know if it is right

My tecaher wants us to split things into vertical and horizontal

So for HORIZONTAL I have
Displacement= 3214m
Velocity= 1000m/s * cos50 = 642m
Time= 5s

VERTICAL
Displacement= 4875
Acceleration = 10m/s^2
Initial velocity =1000m/s
Time= 5s
Final Velocity=950m/s

Your analysis of the horizontal is correct - it does indeed take 5 seconds to reach the cliff. But the vertical is not quite right - you set the vertical component of the initial velocity at 1000 m/s, but it's actually 1000*sin(50) m/s. Make that change and you'll get the correct answer.

When calcium hydroxide reacts with sulphuric acid in a lake what calcium salt is formed

The salt from the sulphuric acid. You should know that. Next time, start another thread please.