Menentukan Bj Alkohol

Menentukan bj alkohol 80% dari larutan alkohol 96%

Dik          :       %₁ alk    = 96%

                        %₂ alk    = 80%

                        V₂ alk     = 50mL

                        W piknometer kosong   = 23,170mg

Dit          :       bj alk 80% ?

Jwb         :       V₁ . %₁ = V₂ . %₂

                        V₁ . 96 = 50mL . 80

                        V₁ = 50ml . 80 / 96

                        V₁ = 4000/96 mL

                        V₁ = 41,6ml

                         

                  Di pipet alkohol 96% sebanyak 41,6ml dan diencerkan dengan aquadest sampai 50ml. 

                  Di timbang alkohol pengenceran menggunakan piknometer 25mL, didapat hasil  penimbangan sebesar 44.320mg sehingga bj dapat dihitung dengan :

                         

                       W alkohol 80%   = (W alcohol+pikno) – (W pikno kosong)

                                                        = (44,320 – 23,170) mg

                                                        = 21,150mg

                        bj     = W / V

                                = 21,150mg / 25ml

                                = 0,8460 g/L (bj alk 80% literatur = 0,8631 g/L)

                  Penyimpangan bj alkohol :

                        (%) Penyimpangan bj       = bj literatur – bj real x 100%bj literatur

                                                                  = 0,8631 – 0,8460 x 100%

                                                                            0,8631

                                                                  = 1,98%