Question

H. to prepare the 5% sucrose solution called for in question 1a, how many moles of sugar did you add? what was the molarity of that solution?

Answer 1

When the concentration is expressed in percent, then that would represent the amount of solute per 100 of the amount of the solution. For 5% sucrose solution, that is 5 g sucrose per 100 g solution. Assuming there is 100 g of solution, the moles of solute is determined using the molar mass of sucrose equal to 342.3 g/mol.

Amount of moles = 5 g sucrose * 1 mol/342.3 g = 0.0146 moles sucrose

The concentration in molarity is the moles of solute per liter solution. Since the solution is very dilute, then we can assume that the density of the solution is almost equal to that of water which is 1,000 g/L.

Molarity = 0.0146 moles/[100g solution * 1 L/1,000 g]
Molarity = 0.146 M sucrose solution