Answers
1. A solution is prepared by mixing 1.00 g of ethanol, C2H5OH, with 100.0 g of water. Calculate the mass percent of ethanol in this solution.
Answer = 0.990% C2H5OH
2. A 135-g sample of seawater is evaporated to dryness, leaving 4.73 g of solid residue (the salts formerly dissolved in the seawater). Calculate the mass percent of solute present in the original seawater.
Answer = 3.50%
3. Although, milk is not a true solution (it is really a suspension of tiny globules of fat, protein, and other substrates in water), it odes contain a dissolved sugar called lactose. Cow's milk typically contains 4.5% by mass of lactose C12H22O11. Calculate the mass of lactose present in 175 g of milk.
Answer = 7.9 g lactose
4. What mass of water must be added to 425 g of formaldehyde to prepare a 40.0% (by mass) solution of formaldehyde? This solution is called formalin, is used to preserve biological specimens.
Answer= 638 g solvent