Stoichiometry table
Short answer: Draw the reaction, then press Ctrl+K and pick Reaction stoichiometry table, or right click the canvas and pick Stoichiometry table. Set the limiting reagent and its mmol or mass. MolDraw fills in MW, equivalents, mmol, mass, volume and the theoretical yield.
The stoichiometry table turns your reaction drawing into the amounts you weigh out. It reads each structure on the canvas and its molecular weight. You type the scale and the equivalents.
- Draw the reactants, a reaction arrow and the product. Put reagents above or below the arrow.
- Press Ctrl+K and pick Reaction stoichiometry table. Or right click the canvas and pick Stoichiometry table….
- In the Lim. column, pick the limiting reagent.
- Type its mmol, or type its Mass (mg).
- Type Equiv for each other reactant or reagent.
- After the reaction, type the Isolated (mg) mass of the product to see the yield.
How MolDraw sorts the structures#
Each separate structure becomes one row. Its place relative to the reaction arrow sets its role.
| Place on the canvas | Row name |
|---|---|
| Behind the tail of the first arrow | Reactant 1, Reactant 2 |
| Above, below or between arrows | Reagent 1, Reagent 2 |
| Past the head of the last arrow | Product 1, Product 2 |
Only splitting arrows count: Straight, Curved, S-curve and Retro. With no such arrow, every structure is a reactant. Reagents typed as text on the arrow do not get a row. Draw them as structures if you need their amounts.
Columns#
| Column | What it shows | You can edit |
|---|---|---|
| Lim. | The limiting reagent. Its equivalents are fixed at 1.00. | Pick one |
| Compound | Row name and formula | No |
| MW | Molecular weight in g/mol | No |
| Equiv | Equivalents relative to the limiting reagent. Default 1. | Yes, except the limiting row |
| mmol | Limiting mmol times equivalents. Default scale is 1 mmol. | Yes, on the limiting row |
| Mass (mg) | mmol times MW | Yes. On the limiting row it sets the scale. On other rows it sets the equivalents. |
| Density (g/mL) | Optional, for liquids | Yes |
| Volume (µL) | Mass divided by density | No |
The product table shows Theor. mmol, Theor. mass (mg), Isolated (mg) and Yield. The yield assumes one product per limiting reagent, a 1:1 ratio. Check the theoretical yield calculator for other ratios.
Share the table#
- Copy table copies tab separated text. Paste it into a spreadsheet or your lab notebook.
- Add to canvas places the table as text next to your scheme.
MolDraw remembers your inputs for each formula in this browser. Open the table again later and your equivalents and densities are still there.
Common problems#
| Problem | Fix |
|---|---|
| Draw the structures of the reaction first. | The canvas is empty. Draw at least one structure. |
| No product table | Draw the product past the arrow head. |
| A reagent shows as a reactant | Move it above or below the arrow, or check that the arrow is a Straight arrow. |
| Two rows for one compound | You drew it twice. Delete the copy, or treat each row on its own. |
For the formula and weight of a single structure, see Names, formula and properties. To learn the maths, try the stoichiometry calculator and the limiting reagent calculator.
Questions and answers
How do I calculate equivalents in MolDraw?
Open the Reaction stoichiometry table, pick the limiting reagent and set its mmol. Type the equivalents of each other row, or type its mass and MolDraw works out the equivalents.
How does MolDraw calculate percent yield?
It divides the isolated mass you type by the theoretical mass and multiplies by 100. The theoretical mass assumes one mole of product per mole of limiting reagent.
Can I export the stoichiometry table to Excel?
Yes. Click Copy table and paste into Excel or Google Sheets. The text is tab separated, so each value lands in its own cell.
Where does MolDraw get the molecular weight?
It calculates the MW from the structure you drew. Check each structure if a value looks wrong.
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