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# van der waals problem2

## van der waals problem

(OP)
hello i am new at this and i cant solve van der waals equation
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

### RE: van der waals problem

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.

### RE: van der waals problem

(OP)
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

### RE: van der waals problem

(OP)
the equation is

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

i need to find volume by use this

### RE: van der waals problem

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(Pj,Ti)=

### RE: van der waals problem

(OP)
it not works
says func isnt defined

### RE: van der waals problem

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

### RE: van der waals problem

(OP)
my worksheets are here thanks for your interest

### RE: van der waals problem

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

(OP)

### RE: van der waals problem

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.

### RE: van der waals problem

(OP)
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

### RE: van der waals problem

(OP)
perfect thanks for help
but it will help me to understand
and problem is solved
thanks and thanks again

### RE: van der waals problem

(OP)
thanks this sheet is very helpful to me

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