This page is an exercise in using a balanced chemical equation and a K value to calculate a concentration. When you press "New Question", a window with a chemical equation, a K value, and a set of concentrations will appear. You will be asked to calculate the value of one the the species in the chemical equation, using the data given. Determine the needed value, enter it in the cell and press "Check Answer". Results appear in the table on the main window. The smaller window can be dragged out of the way, if it covers up any part of the main window.