Question

What is the concentration of sugar (C₁₂H₂₂O₁₁) in mol L^–1 if its 20 g are dissolved in enough water to make a final volume up to 2L?

Answer 1

Solution: We know that 

Molarity of a solution = Number of moles of solute/Volume of solution in Litres

molar mass of C12H22O11 = 12*12. + 1*22 + 11*16  = 342 g / mol 

number of moles of solute = mass of solute / molar mass of solute

                                         = 20/342  = 0.0585 moles 

molarity (M ) of  the solution = 0.0585/2  = 0.0293 M