If 0,5kg of dextrose is dissolved in 600ml of water to produce a solution with a final volumeof 1000ml what is the percentage w/w strength of the solution?

1 Answer
Feb 15, 2018

=45.5%=45.5%

Explanation:

Since the problem calls for the concentration of the solution in %(ww); the suitable formula to solve it is the following:

color(red)(%(w/w)=("mass solute")/("mass solution")%(ww)=mass solutemass solution

where:where:

"mass solute=mass of dextrose"_(solute)=0.5kg=500gmass solute=mass of dextrosesolute=0.5kg=500g

"mass solution"="mass.solute_(dextrose)+mass. solvent_(water)mass solution=mass.solutedextrose+mass.solventwater
"mass solution"=0.5kg+"mass of solvent"_(water)mass solution=0.5kg+mass of solventwater

But, given the volume of water and on the assumption that the density of water @4^oC=1"g/ml"=1"kg/L"4oC=1g/ml=1kg/L, the mass of the solvent (water) can be obtained as shown below.

"mass "=("density")("volume")mass =(density)(volume)
"mass solvent"_(water)=((1kg)/cancel(L)) (600cancel(mL)xx(1cancel(L))/(1000cancel(mL)))
"mass"=0.6kg

This time, masses composing the solution are already known; thus,

"mass solution=mass solute+mass solvent"

"mass solution=mass dextrose+mass water"

"mass solution"=0.5kg+0.6kg

"mass solution"=1.1kg

Therefore:

1.1kg " final mass solution"-=1L " final volume solution"
or
1100g " final mass solution"-=1000mL " final volume solution"
rho " solution"=(1.1g)/(mL)=(1.1kg)/(L)

Using the formula highlighted above, the concentration of the solution is:

color(red)(%(w/w)=("mass solute")/("mass solution")xx100
color(red)(%(w/w)=(0.5cancel(kg))/(1.1cancel(kg))xx100
color(red)(%(w/w)=0.4545xx100
color(red)(%(w/w)=45.5%

Therefore; the concentration of the solution is 45.5%