assign04a-comp1200

// Paul Jernigan, GROUP: none
// Other group members: none
// assign04a.c
// September 22, 2017
// This project was done alone with no outside assistance
// This file adds onto project 3 by using a do-while loop to make sure the temperature input is within the required range.
#include <stdio.h>
#include <math.h>
//*****CONSTANTS*****
#define R 0.08314472    // the ideal-gas constant

int main()
{

   //*****INPUT*****
   // Get input variables as given in instructions
   double moles  = 2,         // mol
          volume = 1,         // L
          a      = 5.536,     // L2atm/mol2
          b      = 0.03049,   // L/mol
          temp;               // Fahrenheit
   // Print user input for temperature fahrenheit
   do {
   printf("Enter the gas temperature (1500 F - 2500 F): ");
   scanf("%lf", &temp);
   } while (temp < 1500 || temp > 2500);


   // Get a and b for gas #2
   printf("Enter a and b for the second gas: ");
   scanf("%lf %lf", &a, &b);
   double absTemp;            // Kelvin
   // Output variables
   double pressureWaalsH20,      // pressure for H20
          pressureWaalsGas2,
          pressureIdeal,      // atmosphere
          pressDiff,          // Difference between H20 and ideal
          pressDiff2,         // Difference between gas 2 and ideal
          diff3,              // Difference between gas 2 and h20
          diff4;
   // Other variables, if needed
   double p,                  // pressure
          nRT;                // nRT


   //*****COMPUTE*****
   // Convert F temp to absolute temp K
   absTemp = fabs((( temp - 32) / 1.8) + 273.15);
   // Van der Waals pressure for H20:
   nRT = (moles * R) * absTemp;
   pressureWaalsH20 = ( nRT / (volume - moles * 0.0305)) - (5.46 * pow(moles, 2) / pow(volume, 2)) ;
   // Van der Waals pressure for gas #2:
   pressureWaalsGas2 = ( nRT / (volume - moles * b)) - (a * pow(moles, 2) / pow(volume, 2)) ;
   // Ideal pressure:
   pressureIdeal = (moles * R) * absTemp;
   // Difference for H20 and ideal pressure
   pressDiff = pressureWaalsH20 - pressureIdeal;
   // Difference for gas #2 and ideal pressure
   pressDiff2 = pressureWaalsGas2 - pressureIdeal;
   diff3 = pressDiff2 - pressDiff;
   diff4 = pressureIdeal - pressureWaalsH20;

   //*****OUTPUT*****
   // Blank line
   printf(" \n");
   // Display Waals pressure with label for H20
   printf("The Waals pressure (atm) for H20: %.2lf \n", pressureWaalsH20);
   // Display Waals pressure with label for gas #2:
   printf("The Waals pressure (atm) for gas #2: %.2lf \n", pressureWaalsGas2);
   // Display ideal pressure with label
   printf("The ideal pressure (atm) Ideal Gas Law: %.2lf \n", pressureIdeal);
   // Blank line 2
   printf(" \n");
   // Identify which gas pressure is greater and the difference, or that they're the same
   if (pressDiff2 > pressDiff) {
      printf("Gas#2 pressure is %.2lf atm higher than H20. \n", diff3);
   }
   else if (pressDiff2 < pressDiff) {
      printf("Gas#2 pressure is %.2lf atm lower than H20. \n", diff3);
   }
   else {
      printf("Gas#2 pressure is the same as H20. \n");
   }
   // Determine which Waals pressure is closer to Ideal pressure
   if (pressureWaalsH20 == pressureWaalsGas2) {
    printf("The Ideal Gas Law describes H20.");
   }else if (pressDiff2 < diff4) {
      printf("The Ideal Gas Law better describes Gas#2.");
   }
   else if (pressDiff2 > diff4) {
      printf("The Ideal Gas Law better describes H20.");
   }


   return 0;
}