When 10 mL of ethyl alcohol (density = 0.7893 g ml-1) is mixed with 20 mL of water (density 0.9971 g mL-1) at 25oC, the final solution has a density of 0.9571 g mL-1. The percentage change in total volume on mixing is

Total weight of alcohol and water=10×0.7893+20×0.9971 Volume of mixture =10×0.7893+20×0.99710.9571=29.08 mL Change in volume =(20+10)−29.08 =0.92 mL % change in volume =0.92×10030≈3.06%                                                              ≈3.1%