what is the concentarion of hyrdoxide ions in 250ml 1.1mol/l of calcium hydroxide

1.1 mole/L Ca(OH)2 has 1.1 mole/L Ca +2 ions and 2.2 mole/L OH -1 ions. It matters not if you have one thimble full or a lake, the concentration is 1.1 mole/L Ca(OH)2 before it separates into the ions.