What is the value of [oh–] in a 0.820 m solution of sr(oh)2?

Strontium Hydroxide Ionizes as follow,

                                       Sr(OH)₂   →   Sr²⁺  +  2 OH⁻
So,
1 mole of Sr(OH)₂ produces 2 moles of Hydroxides,

If the concentration of 1 M Sr(OH)₂ produces 2 M OH⁻ ions then, 0.082 M Sr(OH)₂ will produce,

                                  [OH⁻]  =  2 × 0.082

                                  [OH⁻]  =  0.164 M

Aphysical change is one that you can put in and remove like a ham sandwich. the stuff you put in there can be changem its not permanet. a chemical change is on that can't be change thats permanet. like when you make a cake and bake it. you can't get those ingredients back.