Map HostName To File On Apache

I have done this a million times on Windows, but never on Apache/Ubuntu. I have my portforwarding in the router set-up and I have my host name assigned. But when I type the hostname in Chrome I get a message that shows

The page isn't working. The page didn't send any data

If from within my network I go to localhost it renders the page properly. I am sure there is some silly setting in Apache that I have missed, but I am not sure. The .php file I want to render is located in my /var/www/html directory.

What do I need to do so that my hostname resolves to /var/www/html/index.php?