Question #45384

1 Answer
Nathan L.
Aug 14, 2017

#15.0%#

Explanation:

I'll assume you mean to say #85.0# grams of water (units were left off).

We're asked to find the percent by mass of sucrose, given how much is dissolved in a known amount of water.

The formula for mass percentage of a substance #x# is given by

#ulbar(|stackrel(" ")(" "%"mass"color(white)(l)x = ("mass of"color(white)(l)x)/("total mass") xx 100%" ")|)#

(Here, #x# represents sucrose.)

The total mass of the solution is the mass of the *sucrose plus the mass of *water:

#"total mass" = overbrace(15.0color(white)(l)"g")^"sucrose" + overbrace(85.0color(white)(l)"g")^"water" = color(red)(ul(100.0color(white)(l)"g"#

The mass percentage of sucrose is therefore

#color(blue)(%color(white)(l)"mass sucrose") = (15.0color(white)(l)"g sucrose")/(color(red)(100.0color(white)(l)"g solution")) xx 100% = color(blue)(ulbar(|stackrel(" ")(" "15.0%" ")|)#

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