chem molarity

Consider 1 dm3 (1000 cm3) of the concentrated hydrochloric acid.

Mass of the conc. HCl = volume x density = 1000 x 1.21 = 1210 g
Mass of HCl in the conc. HCl = 1210 x 32.3 % = 391 g
Molar mass of HCl = 1 + 35.5 = 36.5 g mol-1
No. of moles of HCl = mass/(molar mass) = 391/36.5 = 10.7
Molarity of HCl = mol/(V in dm3) = 10.7/1 = 10.7 mol dm-3

2007-03-19 13:41:14 補充：
你可以考慮不同的體積（1 dm^3, 1 cm^3, x dm^3, x cm^3等等），選用 1 dm^3 只是方便計算而己。例如選用 y cm^3 的話：1210 g 變成 1.21y g310 g 變成 0.31y g10.7 mol 變成 0.0107y mol最後摩爾濃渡是 (0.0107y mol) / (1 x 10^-3 y dm^3) = 10.7 mol dm^-3答案是相同的。