Answers

2014-03-03T20:15:03+08:00
to solve for percent by mass of a solution, we have the following formula:

Pm = (mslt / msln) x 100

Pm is percent by mass
mslt is mass of solute
msln is mass of solution (that means, mass of solute + mass of solvent)
in words, the equation is:
percent by mass is equal to mass of solute multiplied by mass of solution multiplied by 100

Given:
mass of sodium chloride (NaCl) = mass of solute = 3.785 grams
volume of water (volume because it's in terms of mL = 43.7 mL
density of water = 1.0 g/mL

we need all given to be in terms of grams because the formula requires "mass" not volume
so, the volume of water must be converted to its mass

to compute for the mass of water let us derive the formula from the formula of density

d = m/v
v = m/d
v = 43.7/ 1
so volume is 43.7 grams (it is given that when the substance is water volume is equal to mass) :-)

given:
mslt = 3.785
mslv (solvent) = 43.7
therefore, msln (solute + solvent) = 3.785 + 43.7 = 47.485

Pm = (3.785/ 47.485) *100
= 0.079709381910076866378856480993998 * 100
= 7.9709381910076866378856480993998
= 7.97%

okay? thanks

2014-03-08T14:46:45+08:00
Percentage by mass of solutes divided by the total mass of the solution times 100.
mathematically:
% by mass of solute= mass of solute  x 100
mass of solution