Since you can staff LibraryH3lp using any XMPP/Jabber client, you can staff your service from a mobile device if you so desire. Popular mobile apps include Xabber (Google Play store), IM+ (all platforms), and Trillian (all platforms) but others may work as well.
For Android, the Xabber app is very nice and recommended.
While your mobile web browser might work in a pinch or for short periods of time, it is not ideal. You really need good push (background) notifications for new chat messages, and that requires a mobile chat app. Push notifications will allow you to do things like allow the device to go idle, lock the device, make another app active, etc, while still receiving reliable alerts of new chat messages. Test your app's notifications thoroughly.
You will also have a difficult time answering questions from your guests using a web browser on a mobile device, because if you need to bring another mobile browser window to the front in the process of answering the question, you might disrupt your network connection to the chat server.
service or protocol = Jabber or XMPP
login = firstname.lastname@example.org (just replace your_username with your actual LibraryH3lp username)
password is your LibraryH3lp password
host = libraryh3lp.com
port = 5222
use old-style SSL = off
If available in your app, you'll want to make sure that you have push notifications turned on for any mobile client you install. That way you'll be notified of incoming chats from guests. These clients will have have various settings you can configure for push notifications, including sounds, alerts, and badges. You might have to check in the app's settings AND in your device's general settings for Notifications (especially for iPhone and iPad).