Can anyone help me to get this PV=nRT working? please.

Just to let you know this is the first time that iam using matlab and have very basic knowledge, if any at all ahah. But basically i have to find the P constant at volume changes between 3 and 5 litres, and at two temperature constants 372k and 472k.

Yet the way i have put it into matlab is does not seem to work and help on this would be appreciated, ill put what ive writen below.

%Ideal gas equation
% a program for calculating the pressure distribution in the ideal gas equation 
%define the tempurature

T1 =372; % units of temperature in kelvi
T2 =427; % units of temperature in kelvin
% define R
R=0.08206; % units L.atm.mol^-1
% define n
n=1;
% define the array of volume in litres
V=3:.01*5:5;
% calculate the pressure disribution (when P is the subject in the ideal % gas equation)
for j=1:10
    P1(j)=T1*R*n/V(j);
    P2(j)=T2*R*n/V(j);
end
% plot the two graphs on the one axis
plot(3,P1)
hold
plot(V,P2)

Answer 1

[Matt Fig]

Change your FOR loop to this:

for jj=1:length(V)   % Note, length(V), not 10!
    P1(jj)=T1*R*n/V(jj);
    P2(jj)=T2*R*n/V(jj);
end

And your call to PLOT to this:

plot(V,P1,'b',V,P2,'r')

Now you can also do things in a more MATLAB-ish way, without loops. This is called vectorization:

P1 = T1*R*n./V;  % Note the ./ rather than /
P2 = T2*R*n./V;

[adam]

Thanks alot for the help, you dont know how much it has helped me out :)

Answer 2

[Image Analyst]

You don't need the for loop, and you need ./ instead of / to do an element by element divide. Try it this way:

%Ideal gas equation % a program for calculating the pressure distribution in the ideal gas equation %define the tempurature
T1 = 372; % units of temperature in kelvin
T2 = 427; % units of temperature in kelvin
% define R
R=0.08206; % units L.atm.mol^-1
% define n
n=1;
% Define the array of volume in litres
V = 3 : .01*5 : 5;
% Calculate the pressure disribution (when P is the subject in the ideal % gas equation)
P1 = T1 * R * n ./ V;
P2 = T2 * R * n ./ V;
% Plot the two graphs on the one axis
plot(V, P1, 'r-', 'LineWidth', 2)
hold
plot(V,P2, 'b-', 'LineWidth', 2)
grid on;
legend('P1', 'P2');
xlabel('V', 'FontSize', 20);
ylabel('P', 'FontSize', 20);
title('PV=nRT', 'FontSize', 20);

By the way, you can highlight your code and click the {}Code icon above the text box so that you don't have to put blank lines in between your lines of code to get them to show up on separate lines.

[Arda Güçlü]

My school project is to write a general function for the ideal gas equation. Have you got any examples about it ?

[Image Analyst]

No. But programming PV=NRT sounds pretty trivial, or could be depending on how simple or fancy you want the program to be.

I don't know what kind of output you are expecting, like a contour plot or image or whatever. If you want, you could start a new question with your attempt at code and a good description of what you want to show/visualize.

Answer 3

[jackie]

can anyone give a loop for this one thankyou

clc; clear all; close all;  
 
% Make a Design program that will Calculate for the value of Pressure, Volume, and Temperature using Ideal gas Law.  
 
% Program Data 
fprintf('This program will be used to calculate for the values of Pressure, Volume, and Temperature using the Ideal Gas Law equation PV=nRT. \n');  
 
% R Constant to be utilized 
R=0.0821; % 
 
% Equation Calculating Code 
fprintf('Choose Variable to Solve. \n'); 
fprintf('Type in P for Pressure \n'); 
fprintf('Type in V for Volume \n'); 
fprintf('Type in T for Temperature \n\n');  
 
Variable = input('Variable: ', 's');  
 
if strcmp(Variable,'P'); 
 fprintf('Calculate for Pressure.\n'); 
 n=input('Type in Number of Moles (mol): '); 
 T=input('Type in Temperature value in deg Celsius (°C): '); 
 V=input('Type in Volume value in Liters (L): '); 
 P=[n*R*(T+273)]/V; % Calculating for Pressure with converted Temperature from °C to K 
fprintf('Pressure = %f atm \n', P); % Final Answer 
elseif strcmp(Variable,'V'); 
    fprintf('Calculate for Volume.\n'); 
    n=input('Type in Number of Moles (mol): '); 
    T=input('Type in Temperature value in deg Celsius (°C): '); 
    P=input('Type in Pressure value in Atmospheric Pressure (atm): '); 
    V=[n*R*(T+273)]/P; % Calculating for Volume with converted Temperature from °C to K 
    % fprintf('Volume = %f L \n', V); % Final Answer 
elseif strcmp(Variable,'T'); 
    fprintf('Calculate for Temperature.\n'); 
    P=input('Type in Pressure value in Atmospheric Pressure (atm): '); 
    V=input('Type in Volume value in Liters (L): '); 
    n=input('Type in Number of Moles (mol): '); 
    T=(P*V)/(n*R)-273; 
end

[Image Analyst]

@jackie here is one way:

% Make a Design program that will Calculate for the value of Pressure, Volume, and Temperature using Ideal gas Law.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;
% R Constant to be utilized
R=0.0821; %
button = 'Yes';
while strcmpi(button, 'Yes')
    % Program Data
    fprintf('This program will be used to calculate for the values of Pressure, Volume, and Temperature using the Ideal Gas Law equation PV=nRT. \n');
    % Equation Calculating Code
    fprintf('Choose Variable to Solve. \n');
    fprintf('Type in P for Pressure \n');
    fprintf('Type in V for Volume \n');
    fprintf('Type in T for Temperature \n\n');
    Variable = input('Variable: ', 's');
    if strcmpi(Variable,'P')
        fprintf('Calculate for Pressure.\n');
        n=input('Type in Number of Moles (mol): ');
        T=input('Type in Temperature value in deg Celsius (°C): ');
        V=input('Type in Volume value in Liters (L): ');
        P=[n*R*(T+273)]/V; % Calculating for Pressure with converted Temperature from °C to K
        fprintf('Pressure = %f atm \n', P); % Final Answer
    elseif strcmpi(Variable,'V')
        fprintf('Calculate for Volume.\n');
        n=input('Type in Number of Moles (mol): ');
        T=input('Type in Temperature value in deg Celsius (°C): ');
        P=input('Type in Pressure value in Atmospheric Pressure (atm): ');
        V= n*R*(T+273) / P; % Calculating for Volume with converted Temperature from °C to K
        % fprintf('Volume = %f L \n', V); % Final Answer
    elseif strcmpi(Variable,'T')
        fprintf('Calculate for Temperature.\n');
        P=input('Type in Pressure value in Atmospheric Pressure (atm): ');
        V=input('Type in Volume value in Liters (L): ');
        n=input('Type in Number of Moles (mol): ');
        T=(P*V)/(n*R)-273;
    end
    % Tell user the results and ask if they want to keep going.
    message = sprintf('T = %f\nP = %f\nV = %f\nn = %f\n', T, P, V, n);
    fprintf('%s', message);
    reply = questdlg(message, 'Results', 'OK - Continue', 'Quit', 'OK - Continue');
    if strcmpi(reply, 'Quit')
        % User said Quit, so exit.
        break;
    end
end