Question

Joe Chemist wants to make 3 different saturated solutions of Ca(OH)2. He places the same mass of solid Ca(OH)2 into each of 3 different beakers (A, B, C). Into beaker A, he adds 100 mL of water, into beaker B he adds 120 mL of water, and into beaker C he adds 150 mL of water. After stirring each solution for 30 minutes there is still some solid present on the bottom of beakers A and B.

Which beakers contain saturated solutions of Ca(OH)2?

Does it matter how much water is used in making a saturated solution? Explain.

Is the [OH-] the same or different in beakers A and B? Explain.

Answer 1

if beakers A and B have solids, then, the solid is no longer soluble in such amount of volume, 100, 120 mL

then, they msut be saturted solutions

choose A + B = Saturated

b)

If we talk about mass, then it does

if we talk about concentration, it will not matter, since solubility is the same at constant Temperature

c)

[OH-] amount is the same in A and B, since they are saturated

it is not the same as in C, since all [OH-] is present in solution, whereas in A and B there is OH- in solid state