A solution is prepared by adding 2 grams of substance a to 18 grams of water. How do you calculate the mass percent of the solute?

Percent by mass is the mass of the solute divided by the mass of the solution, multiplied by 100.

##"% by mass" = "mass of solute"/"mass of solution" × 100 %##

##="mass of solute"/"mass of solute + mass of solvent"× 100 %##

Step 1 — Determine the mass of the solute.

The mass of solute is 2 g.

Step 2 — Determine the mass of solution.

##"mass of solution" = "mass of solute + mass of solvent "="2 g + 18 g = 20 g"##.

Step 3 — Determine percent by mass of the solute.

##"% by mass" = "mass of solute"/"mass of solution" × 100 % = (2 color(red)(cancel(color(black)("g"))))/(20 color(red)(cancel(color(black)("g")))) × 100 % = 10 %##

The mass percent of the solute is 10 %.