Molaritas
1. Hitunglah molaritas dari masing-masing larutan berikut ini.
a. gliserol (C3H8O3) 72 gram dilarutkan dalam 1.000 ml air,
Jawab :
Mr = ((Ar C x 3 + (Ar H x 8) + (Ar O x 3))
= ((12 x 3) + (1 x 8) + (16 x 3))
= 92
mol (n) = massa : Mr
= 72 : 92
= 0,78 mol
molaritas = n : v (dalam liter)
= 0,78 : 1
= 0,78 M
b. metanol (CH3OH) 20 gram dilarutkan dalam 100 ml air. (Ar C = 12, Ar H = 1, Ar O = 16)
Mr = ((Ar C x 1) + (Ar H x 4) + (Ar O x 1))
= ((12 x 1) + (1 x 4) + (16 x 1))
= 32
mol (n) = massa : Mr
= 20 : 32
= 0,625 mol
molaritas = n : v (dalam liter)
= 0,625 : 0,1
= 0,0625 M
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