Sodium metal dissolves in liquid mercury to form a solution called a sodium amalgam. The densities of Na(s) and Hg(l) are 0.97 g/cm3 and 13.6 g/cm3, respectively. A sodium amalgam is made by dissolving 1.0 cm3 Na(s) in 20.0 cm3 Hg(l). Assume that the final volume of the solution is 21.0cm3. (a) calculate the molality of Na in the solution. (b) calculate the molarity of Na in the solution. (c) for dilute aqueous solutions, the molality and molarity are generally nearly equal in value. Is that the case for sodium amalgam described here?
3 answers
determine the final concentration of a 20.ml 5.M NaCl solution if 30Mml of water has is added to the solution?
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Find grams Na and grams Hg.
g Na = 0.97 g/cc x 1 cc = 0.97g
g Hg = 13.6 g/cc x 20 cc = about 270 g (all of this is about. You should redo the math on your calculator. It will be better than my estimates.)
molality = moles Na/kg solvent.
moles Na = g Na/molar mass Na.
kg solvent = 0.270
Substitute and solve for m.
For molarity. M = moles/L soln
moles Na you calculated above.
L soln = 21 cc = 0.021 L.
Substitute into M = moles/L and calculate.
The c part you can answer after you've completed a and b parts.
Post your work if you get stuck.
g Na = 0.97 g/cc x 1 cc = 0.97g
g Hg = 13.6 g/cc x 20 cc = about 270 g (all of this is about. You should redo the math on your calculator. It will be better than my estimates.)
molality = moles Na/kg solvent.
moles Na = g Na/molar mass Na.
kg solvent = 0.270
Substitute and solve for m.
For molarity. M = moles/L soln
moles Na you calculated above.
L soln = 21 cc = 0.021 L.
Substitute into M = moles/L and calculate.
The c part you can answer after you've completed a and b parts.
Post your work if you get stuck.
0 answers