[Kaleyrvt]

The solubility product of calcium hydroxide, Ca(OH)2, is 7.9 x 10-6 at 25ºC. Will a precipitate form when 100mL of 0.10 mol/L of CaCl2 solution and 50.0 mL of 0.70 mol/L of NaOH solution are combined? Show your work.

This is my work, but I dont know if I am even close-can someone check it to ensure I did it right?

[CaCl2] = 0.10 mol/L x 100 ml(0.1 L)   =  0.066 mol/L
                               150 mL(0.15 L)

[NaOH] = 0.70 mol/L x 50 ml(0.05 L)    =  0.233 mol/L
       150 mL(0.15 L)

Ksp = [CaCl2] [NaOH] = 0.015 => 1.5 x 10 -2

Since Ca(OH)2 = 7.9 x 10-6   which is < 1.5 x 10 -2 then no precipitate will form.

Thanks all ! hope to hear form you soon!

[AWK]

Ksp = [Ca²⁺] [OH^-]² = ?

A final answer is correct, but your calculations are wrong

syntax corrected

[Borek]

Ksp = [Ca²⁺][OH^-]²

[Kaleyrvt]

so then where did I go wrong??All of it??? How do I find values for [Ca2+][OH-]2
Sorry, just don't quite understand where to fix it...

[Borek]

You mix dissociated salt with dissociated base - you have to calculate concentrations of ions and put them into Ksp formula.

[Kaleyrvt]

I am sorry i am completely lost--god I feel like an idiot..

[Borek]

You have 0.233M solution of NaOH - what ions and in what concentrations does it contain?

[Kaleyrvt]

The NaOH contains [Na+] and [OH-] ions...how do I figure out the concentrations?
I really am trying----I am even looking through my notes

[Borek]

If there is 1 mole of NaOH dissolved - how many moles of Na⁺ appeared in the solution?

Note: [Na⁺] usually means concentration of Na⁺, you don't need square brackets around ions when you refer to them.

[Kaleyrvt]

0.5 moles of Na+?

[Borek]

How many Na atoms per NaOH molecule?

[Kaleyrvt]

1 Na atom in NaOH

[Borek]

So how 1 mole of NaOH could produce 0.5 mole of Na⁺?

[Kaleyrvt]

divide 0.233M by 2= # of moles of Na+???

[Dan]

Think about this:

If every apple has one stalk, how many stalks do a dozen apples have?

Similarly if one NaOH unit has one Na, how many Na⁺ ions will 1 mol of NaOH units form?