ENVIRSC 2Q03 Lecture Notes - Lecture 4: Sodium Hydroxide, Iron Sulfide, Hematite
12 Dec 2016
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Concentration units (3) mole concentration units u(cid:374)its (cid:396)efle(cid:272)ti(cid:374)g p(cid:396)opo(cid:396)tio(cid:374)s i(cid:374) (cid:449)hi(cid:272)h (cid:272)o(cid:373)(cid:271)i(cid:374)e (cid:894)(cid:396)e(cid:373)e(cid:373)(cid:271)e(cid:396) the (cid:862)(cid:373)ole(cid:863)? (cid:895); 2 variants, molarity & molality (a) molarity = (cid:894)(cid:373)ol/l o(cid:396) (cid:862)m(cid:863)(cid:895) (cid:373)ole a(cid:373)ou(cid:374)t su(cid:271)sta(cid:374)(cid:272)e solute i(cid:374) (cid:1005)l sol(cid:448)e(cid:374)t, (cid:373)ola(cid:396) (cid:272)o(cid:374)(cid:272)e(cid:374)t(cid:396)atio(cid:374); m calculation requires formula weight (fw) Given: ca = 400ppm = 400mg/l; k = 380ppm = 380mg/l. Fw (or aw): mgfwca = 40. 078mg/mmol; mgfwk = 39. 098mg/mmol. Ca(mol/l) = 400mgca/l x 1mmolca/40. 078mgca x 1mol/1000mmol = 0. 00998m = 9. 98x10-3m=9. 98mm. K(mol/l) = 380mgk/l x 1mmolk/39. 098mgk x 1mol/1000mmol = 0. 00972m = 9. 72x10-3m=9. 72mm. Uses same prefixes or power of 10 notation to convert molar (mol/l, m) to millimolar (mmol/l or mm) Ex2: 2. 5 grams aluminum sulfate or alum, al2(so4)3 was completely dissolved in 1 l water. Find molar concentrations of al(aq) & so4(aq) using appropriate units. 2- gfwal2(so4)3 = 2(26. 98)+(32. 07 + (16x4))x3 = 342. 17g (in 1 mol) mol al2(so4)3 = 0. 0073mol or 7. 3mmol. Hw: transpose dissolved [al] & [so4] above to mass concentration in units (mg/l).
