Ishwar S. answered • 06/06/19
University Professor - General and Organic Chemistry
By definition, a 12%-(w/w) sucrose solution contains 12 g of sucrose dissolved in 100 g of solution.
How much sucrose will be present in 65 g of this 12%-(w/w) sucrose solution?
65 g solution x (12 g sucrose / 100 g solution) = 7.8 g of sucrose
A solution consists of a solute (sucrose) and a solvent (water). In a w/w-solution, the mass of the solvent is:
g of solution = g of sucrose + g of water
65 g = 7.8 g + ? g of water
? g of water = 65 - 7.8 = 57.2 g water
To summarize, take 7.8 g of sucrose and dissolve it in 57.2 g of water to give 65 g of the 12%-(w/w) sucrose solution.
To confirm that the math is correct, calculate the %-(w/w) concentration using these numbers,
%-w/w = (7.8 g sucrose / 65 g solution) x 100% = 12% !!
