van der waals problem 2

[silentnight83]

hello i am new at this and i cant solve van der waals equation
on mathcad
i tried R:=0.0821 Latm\mol K
P:=1,2...3 atm T:=283,287...333 K a:=3.59 b:=0.0427

and write the equation

f(V):=[(P+(a/V^2))*(V-b)]-[R*T]

now what should i do to get volume values from this equation
i tried everything i couldnt find some examples similar
plz help on it
thanks for helps

 

[IRstuff]

What do you mean "get volume" You've defined a function whose input is volume, which makes it an unknown. Unless you have values for the function, you have two unknowns and one equation.

TTFN

FAQ731-376

 

[silentnight83]

i see, it s my fault
ihave pressure, temparature ,R ,a,b
i defined all i have 3 diffent pressure value
and 10 diffrent temp value (it means 30 diffrent volume values)i want to find them with van der waals

if i had have volume values i could easly found temperature
or pressure parameters but when volume is variable , it
is more complex
i think it can be solved by given-root
but i don know how

 

[silentnight83]

the equation is

[P+(a/v^2)]*(V-b)=R*T

i need to find volume by use this
sorry about my poor english

 

[IRstuff]

The given-solve functionality is well documented in the help files. The only adder you need to do is to assign the find(V) to a function whose inputs are P and T, i.e.,
Given
[P+(a/v^2)]*(V-b)<CTRL>=R*T
func(P,T):find(V)
i:1;10 j:1;3

func(P_j,T_i)=

TTFN

FAQ731-376

 

[silentnight83]

it not works
says func isnt defined

 

[IRstuff]

You need to post the worksheet, preferrably in v11 format.

TTFN

FAQ731-376

 

[silentnight83]

my worksheets are here thanks for your interest

 

[IRstuff]

I don't have a version above 11, so I can't read the files you posted.

TTFN

FAQ731-376

 

[silentnight83]

then i copy them to word(.doc)

 

[IRstuff]

Did you even read the help files?

You need to supply a guess value for V. You futher compound whatever other problems you might have by not using units, but also using V, which is a built-in unit designating volts.

TTFN

FAQ731-376

 

[silentnight83]

i am working on it for P:=1 or P:=2 or P:=3
but when i want to find P:=1,2..3 it say
this value must be scalar or matris
my problem is finding V for different P and T (indices)
look at new worksheets

 

[excognito]

Is the attached of any assistance?

 

[silentnight83]

perfect thanks for help
i have no idea about vectors and matrises on mathcad
but it will help me to understand
and problem is solved
thanks and thanks again

 

[IRstuff]

Attached is the way your sheet is ought to be done.

TTFN

FAQ731-376

 

[silentnight83]

thanks this sheet is very helpful to me