pH calc (1 Viewer)

[indeed]

Answer is D

How would you solve this question using calculations (of course just by looking at it it's D cause basic pH, but im curious about calc)

Thanks

 

[SadCeliac]

View attachment 39174

Answer is D

How would you solve this question using calculations (of course just by looking at it it's D cause basic pH, but im curious about calc)

Thanks

ksp values and the Ksp dissociation equilibrium:

Ca(OH)2 solid <--> Ca2+ + 2OH-

You are given that
on the data sheet

Therefore [Ca2+][OH-]^2 = 5.02*10^-6

Therefore given Ca concentration is 0.0015, you can solve for OH-

 

[SadCeliac]

ksp values and the Ksp dissociation equilibrium:
You are given that
View attachment 39175 on the data sheet

Therefore [Ca2+][OH]^2 = 5.02*10^-6

Therefore given Ca concentration is 0.0015, you can solve for OH-

That's my best guess at least, although I kinda tried it now and couldn't get any of the given answers

 

[indeed]

Oh ok cheers, though doing it that way gives 12.76 and assumes Ca2+ conc is same as Ca(OH)2

I tried using RICE table but got relatively close to answer but not it

 

[SadCeliac]

Oh ok cheers, though doing it that way gives 12.76 and assumes Ca2+ conc is same as Ca(OH)2

I tried using RICE table but got relatively close to answer but not it

hmmmm I still assume it still has something to do with Ksp

I'll try it on paper again in a sec haha

 

[nsw..wollongong]

u know that Ca(OH)2 <--> Ca2+ + 2OH-
so pOH = -log(0.0015 x 2)
pH = 14 - that value

u get 11.48
u dont need to use Ksp

 

[SadCeliac]

u know that Ca(OH)2 <--> Ca2+ + 2OH-
so pH = -log(0.0015 x 2)
pOH = 14 - that value

u get 11.48
u dont need to use Ksp

I feel silly

 

[nsw..wollongong]

I feel silly

its okay ur just overthinking it

 

[indeed]

u know that Ca(OH)2 <--> Ca2+ + 2OH-
so pH = -log(0.0015 x 2)
pOH = 14 - that value

u get 11.48
u dont need to use Ksp

Oh ok thanks, but can you say that the conc of hydroxide ions is in molar ratio to Ca(OH)2 though (since 0.0015 is initial conc., would you need to logically do RICE)

 

[nsw..wollongong]

Oh ok thanks, but can you say that the conc of hydroxide ions is in molar ratio to Ca(OH)2 though (since 0.0015 is initial conc., would you need to logically do RICE)

no u don't even need to do rice, u just need to know that there's 2 of OH so u just multiply the given conc by 2

 

[indeed]

no u don't even need to do rice, u just need to know that there's 2 of OH so u just multiply the given conc by 2

Oh ok thanks