The molar mass of sodium bicarbonate (NaHCO3) is 84.006 g/mol.
Case matters: CO is carbon monoxide, Co is
cobalt. Brackets and hydrates are fine — try
or
.
| Element | Atoms | Atomic mass | Mass contributed | Percent |
|---|---|---|---|---|
| Carbon (C) | 1 | 12.011 | 12.011 | 14.30% |
| Hydrogen (H) | 1 | 1.0080 | 1.008 | 1.20% |
| Sodium (Na) | 1 | 22.98976928 | 22.990 | 27.37% |
| Oxygen (O) | 3 | 15.999 | 47.997 | 57.13% |
| Total | 6 | 84.006 | 100.00% |
12.011 + 1.008 + 22.990 + 47.997 = 84.006 g/mol
Grams and moles
25 g of sodium bicarbonate is 0.2976 mol, because 25 ÷ 84.006 = 0.2976.
These elements have no single atomic weight. Their isotopic mix varies slightly depending on where on Earth the sample came from, so the figure used here is the conventional value IUPAC publishes for when one number is needed: carbon is 12.011, and really lies between 12.0096 and 12.0116; hydrogen is 1.0080, and really lies between 1.00784 and 1.00811; oxygen is 15.999, and really lies between 15.99903 and 15.99977.
Baking soda is 84.006 g/mol. Sodium accounts for 27.37% of that, oxygen 57.13%, carbon 14.30% and the single hydrogen 1.20%.
Heat it above about 50 degrees Celsius and two formula units decompose into one sodium carbonate, one water and one carbon dioxide. The mass arithmetic is worth doing: 168.012 grams of bicarbonate produce 105.988 of carbonate, 18.015 of water and 44.009 of gas, which sums back to 168.012. Nothing is lost, but two thirds of the original mass leaves the pan as vapour and gas, which is what makes a cake rise.
The proper name is sodium hydrogen carbonate, and the older name sodium bicarbonate survives mostly through cooking. The hydrogen in the middle of the formula is the reason it works as a mild antacid: it can accept a proton from stomach acid and release carbon dioxide, which is also why swallowing too much of it is uncomfortable.