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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

mathematically:

% by mass of solute=