Weight conversion

[Nikanon]

I am fetid to figure out how to do weight conversions (mostly for self-interest). I have started by trying to convert an amount of sodium carbonate anhydrous to sodium carbonate monohydrated, being sure to keep the same amount of chemical. I started by adding up the weight of sodium carbonate (Na2CO3 = 105.9869g/mol) and then dividing this by monohydrated sodium carbonates weight to get the percentage and then subtracted it from 100 to see the increase of weight by percentage. (Na2CO3 + H2O = 124.002 g/mol). The equation was 105.986/124.002 = 0.8547 = 85.47%. 100% - 85.47% = 14.53%. So based on my findings, if I had 50g of anhydrous sodium carbonate, I would need 14.53% more in grams of monohydrated to equal 57.3g, giving me the same amount of chemical. Am I accurate in my calculations? Or did I mess up somewhere?

 

[degruyl]

124.002/105.986*50 = 58.5 (because that is all you could measure anyway)

Are you sure of the molecular weight (or, more to the point the water content) of the monohydrated sodium carbonate? (actually, I just checked: your numbers look fine).

 

[hrst]

Forget the percentages and take one step at a time to make it easier, so, just first convert the amount called in the recipe from grams to mols, using the molar weight of the chemical called in the recipe.

Then, convert the mols back to grams, using the molar weight of the chemical you have.

 

[Christopher Walrath]

The old Amphoto data guides had these conversions in them. I copied one up onto my own website.

 

[Gerald C Koch]

Eliminate the step calculating the percentage! If you wish to calculate the weight of the monohydrate then multiply by the factor MW monohydrate / MW of anhydrous. To go the other way invert the fraction.