How are mixtures different than pure substances?

Question 5 options:

Mixtures contain only one type of atom.

Mixtures can be separated physically.

Mixtures are less dense than pure substances.

Mixtures have lower boiling points.

Using a value of ksp = 1.8 x 10-2 for the reaction pbcl2 pb+2(aq) + 2cl -(aq). if the value of ksp was determined to be only 1.2 x 10-2: too much solid has dissolved. additional precipitate is forming. the solution is unsaturated. the ions are now combining to reduce their concentrations.

Which type of substance ionizes partially and gives off hydrogen ions when dissolved in water? a. strong acid b. strong base c. weak acid d. weak base

Can someone me with 3 and 4 plz. this is for masteries test.