The Museum of HP Calculators


Ideal Gas Equation of State for the HP-33E/C

This program is Copyright © 1978 by Hewlett-Packard and is used here by permission. This program was originally published in "HP-33E Student Engineering Applications".

This program is supplied without representation or warranty of any kind. Hewlett-Packard Company and The Museum of HP Calculators therefore assume no responsibility and shall have no liability, consequential or otherwise, of any kind arising from the use of this program material or any part thereof.

Overview

Many gases obey the ideal gas laws quite closely at reasonable temperatures and pressures. This program calculates any one of the four variables when data for the other three and the universal gas constant are entered. Likewise the value of the universal gas constant can be determined by entering data for the four variables.

Equation:

PV = nRT

Where:
       P is the absolute pressure
V is the volume
n is the number of moles present
R is the universal gas constant
T is the absolute temperature

Values of the Universal Gas Constant

Value of R

Units of R

Units of P

Units of V

Units of T

8.314

N-m/g mole- K

N/m2

m3/g mole

K

83.14

cm3-bar/g mole- K

bar

cm3/g mole

K

82.05

cm3-atm/g mole- K

atm

cm3/g mole

K

0.08205

l-atm/g mole- K

atm

l/g mole

K

0.7302

atm-ft3/lb mole-°R

atm

ft3/lb mole

°R

10.73

psi-ft3/lb mole-°R

psi

ft3/lb mole

°R

1545

psf-ft3/lb mole-°R

psf

ft3/lb mole

°R

Remarks:

Instructions

Step

Instructions

Input Data/Units

Keys

Output Data/Units

1

Enter program

     

2

Set display and initialize

 

f FIX 2 f PRGM

 

3

Input variables*

 

 

 

 

 Pressure

P

ENTER  

 

 

 Volume

V

R/S

 

 

 Number of moles

n

ENTER  

 

 

 Universal gas constant**

R

ENTER

 

 

 Absolute temperature

T

 

 

4

a) To calculate P or V

 

R/S

P or V

 

 or

 

 

 

 

 b) To calculate n, R or T

 

R/S R/S

n, R or T  

5

To change conditions:

 

 

 

 

a) Go to step 3, or,

 

 

 

 

b) Store new variable in proper register (see register contents) and store 1 in register of variable to be calculated, then,

 

 

 

 

for P or V

 

GSB 16

P or V

 

 or,

 

 

 

 

for n, R or T

 

GSB 16 R/S

n, R or T 

 

* Note: variables must be input in order shown. Input zero for variable to be calculated.

 

 

 

 

** Be sure R is in units compatible with units of variables.

 

 

 

Example

0.63 moles of air are enclosed in 25000 cm3 at 1200K. What is the pressure in bars? In atmospheres? Assume and ideal gas. (R = 83.14 cm3-bar/g mole-K or 82.05 cm3-atm/g mole-K)

Keystrokes          Display
f FIX 2 f PRGM
0 ENTER
25000 R/S
.63 ENTER
83.14 ENTER
1200 R/S            2.51    (bars)
82.05 STO 4
GSB 16              2.48    (atm)

The Program

LINE    CODE    KEYS
 00             f CLEAR PRGM
 01     12 28   GSB 28
 02     23  2   STO 2
 03        22   Roll dn
 04     12 28   GSB 28
 05     23  1   STO 1
 06        22   Roll dn
 07        74   R/S
 08     12 28   GSB 28
 09     23  5   STO 5
 10        22   Roll dn
 11     12 28   GSB 28
 12     23  4   STO 4
 13        22   Roll dn
 14     12 28   GSB 28
 15     23  3   STO 3
 16     24  3   RCL 3
 17     24  4   RCL 4
 18        61   x
 19     24  5   RCL 5
 20        61   x
 21     24  1   RCL 1
 22     24  2   RCL 2
 23        61   x
 24        71   ÷
 25        74   R/S
 26     15  3   g 1/x
 27     13 00   GTO 00
 28     15 61   g x!=0
 29     15 12   g RTN
 30        22   Roll dn
 31         1   1
 32     15 12   g RTN

Register Use

R1  P
R2  V
R3  n
R4  R
R5  T

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