How many grams of #"KNO"_3# should be dissolved in water to make #"500.0 g"# of a #"20.0-ppm"# solution?
1) 1.00 x 10^-3 g
2) 1.00 x 10^-4 g
3) 1.00 x 10^-1 g
4) 1.00 x 10^-2 g
1) 1.00 x 10^-3 g
2) 1.00 x 10^-4 g
3) 1.00 x 10^-1 g
4) 1.00 x 10^-2 g
1 Answer
Explanation:
As you know, a solution's concentration in parts per million tells you the number of grams of solute present for every
#10^6 = 1,000,000#
grams of the solution. In your case, the target solution must have a concentration of
This means that the mass of potassium nitrate needed to make this solution is equal to
#500.0 color(red)(cancel(color(black)("g solution"))) * "20.0 g KNO"_3/(10^6color(red)(cancel(color(black)("g solution")))) = color(darkgreen)(ul(color(black)(1.00 * 10^(-2) quad "g")))#
The answer is rounded to three sig figs.
So, if you dissolve