Stuck on chemistry problem due tonight

Question

What is the pH and pOH of a solution made by adding water to 23.2 grams of calcium hydroxide until the volume of the solution is 2500 ? (Hint: solve for molarity first !

pOH?round to 1 decimal place

pH?round to 1 decimal place

Answer 1

Hi Avery!

This is a great question!

First I am going to assume the volume is in mL.

Now the first thing is to remember calcium hydroxide is a strong base (i.e. it fully dissociates in water).

Ca[OH]2 -> [Ca]2+ + 2[OH]-

Now we can calculate the moles of OH- (hydroxide ion)

Molar Mass of Calcium Hydroxide is 74.093 g.

23.2 g Ca[OH]2 * (1 mole/74.093 g) * 2 moles of Hydroxide/1 mole of calcium hydroxide = n

Now we calculate the molarity of hydroxide.

M [OH-] = n/V

where M is molarity

n is moles of hydroxide

V is volume of solution in liters

V = 2.5 L

M = 23.2*(1/74.093)*2/2.5

From the molarity, we can figure out the pOH

pOH = -log(M).

Once we have pOH, we can figure out pH.

pH + pOH = 14

pH = 14 - pOH