# Question #45384

##### 1 Answer

#### Explanation:

I'll assume you mean to say **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

#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%" ")|)#