What is the percent by mass of KBr if 58.2 grams are dissolved in 344 grams of water?

2 Answers
Apr 20, 2018

Answer:

#14.5%#

Explanation:

The idea here is that you need to determine how many grams of potassium bromide will be present for every #"100. g"# of this solution, which is what the solution's percent concentration by mass represents.

If you dissolve #"58.2 g"# of potassium bromide in #"344 g"# of water, the total mass of the solution will be

#"58.2 g + 344 g = 402.2 g"#

So this solution contains #"58.2 g"# of potassium bromide in #"402.2 g"# of the solution, which means that in #"100. g"# of this solution you will have

#100. color(red)(cancel(color(black)("g solution"))) * "58.2 g KBr"/(402.2 color(red)(cancel(color(black)("g solution")))) = "14.5 g KBr"#

You can thus say that the solution's percent concentration by mass is equal to

#color(darkgreen)(ul(color(black)("% m/m = 14.5% KBr")))#

The answer is rounded to three sig figs, the number of sig figs you have for your figures.

Apr 20, 2018

Answer:

The percent by mass of #"KBr"# is #"14.4%"#.

Explanation:

#"%(m/m)"=("mass of solute")/("mass of solution")xx100#

The mass of the solution is the mass of the solute and solvent.

The given mass of the solute #"KBr"# is #"58.2 g"#.

The mass of the solution is #"58.2 g KBr + 344 g H"_2"O"="404.2 g"#

Plug in the known values and solve.

#"%(m/m)"=(58.2"g KBr")/(404.2"g solution")xx100=14.4%#