gchem questions

[mgdent]

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When asked to calculate ksp, I am somewhat confused about when to use each of the following. For instance...

When given PbF2- --> Pb2+ + 2F- and told that the [Pb2+]=1x10-3, Calculate ksp for PbF2 I would go right to MX2=4x^3 so 4(1x10-3)^3

but you could also use an ICE table and get Ksp= (1x10-3)(2x^2). Is this the same thing? I dont have a calculator in front of me (sorry if this is a dumb question lol)

Also, I am using the Kaplan book and it has an example for calculating the density at NON stp
ex- What is the density of HCl gas at 2 atm, 45 C?
V2= (1 atm)(22.4 L/mol)(318 K) all over (273 K)(2 atm) ... What I dont understand here is why the values for P1 V1 T1 are the STP values.

Thanks SO much!

 

[PreDental88]

When asked to calculate ksp, I am somewhat confused about when to use each of the following. For instance...

When given PbF2- --> Pb2+ + 2F- and told that the [Pb2+]=1x10-3, Calculate ksp for PbF2 I would go right to MX2=4x^3 so 4(1x10-3)^3

but you could also use an ICE table and get Ksp= (1x10-3)(2x^2). Is this the same thing? I dont have a calculator in front of me (sorry if this is a dumb question lol)

Also, I am using the Kaplan book and it has an example for calculating the density at NON stp
ex- What is the density of HCl gas at 2 atm, 45 C?
V2= (1 atm)(22.4 L/mol)(318 K) all over (273 K)(2 atm) ... What I dont understand here is why the values for P1 V1 T1 are the STP values.

Thanks SO much!

For the first question, the products are the same, 4x^3 is a more simplified form of (1x10-3)(2x^2) and since x=1x10-3, it is essentially x^3

For the second question, I'm not too sure why they used STP values for P1, V1, and T1, but could you use the equation d = P(MM) / RT to solve for density? using R=.08 molK/Latm