5.0 grams of sugar are dissolved in 150 grams of water what is the mass percent of sugar in the solution?

Question

 5.0 grams of sugar are dissolved in 150 grams of water what is the mass percent of sugar in the solution?

Answer 1

Mass percent means exactly what it says. 

It is the mass fraction converted to a percent:

 

some weight / total weight = the percent number / 100

 

They want the mass percent of sugar -- 

mass sugar/ total mass = x / 100

 

The mass of the sugar is given = 5.

 

Be careful on the total mass of the solution.  You HAD 150 grams of water.  But you ADD the 5 grams of sugar.  So the solution now weighs 150 + 5 = 155 grams.

 

(Always make sure you are dealing in the same units and they haven't tried to trick you by throwing in some numbers in grams and others in kilograms.)

 

 

So the equation you need to solve by cross multiplying is:

 

5/155 = x/100

 

(write those sideways slanted fractions as up and down fractions and you will see the cross multiplying more easily.)