A 45.0g aqueous solution is made using 10.0g of ethanol. What percentage of the solution is ethanol?
Your aim here is to find the mass of ethanol present in
Now, this solution has a uniform composition, meaning that the solvent and the solute are evenly mixed. This implies that you can use this given composition to figure out how many grams of ethanol would be present in
#100 color(red)(cancel(color(black)("g solution"))) * overbrace("10.0 g ethanol"/(45.0color(red)(cancel(color(black)("g solution")))))^(color(purple)("known composition")) = "22.2 g ethanol"#
#color(green)(bar(ul(|color(white)(a/a)color(black)("% m/m" = "mass of ethanol in 100 g solution" = 22.2%)color(white)(a/a)|)))#
The answer is rounded to three sig figs.