Reaction Balancing and Molecular Weight Calculation Tool
A really quite useful webMathematica application by Theodore Gray
Images taken from my Periodic Table Table
Enter a chemical reaction in the field below and the system will automatically balance the reaction for you, calculating the appropriate coefficient to put in front of each compound to balance the total number of atoms of each element on both sides. Enter the formula using the standard element abbreviations (case matters!) and use -> for the reaction arrow, as in the default example.
You can also just enter a single compound to get its molecular weight and composition.
Don't include any coefficients in front of the reactants: The system will add them automatically for you.