Question

74 Percent Concentration -The amount of solute dissolved in a fixed amount of solvent is called the concentration of the solution. Concentrations are typically expressed as Mass al.) (% m/m) which is the mass of the solute (g) divided by the mass of the solution [solute+ solvent] (g)x 1000/0; or as Volume ol.) (% v/v ) which is the volume of the solute in a fixed volume of solution (1O0mL of solution) x 1000/0; or less commonly in the laboratory, but common in hospitals and pharmacies, as a Mass Volume () (m/v 6) which is the mass in g of the solute in 100mL of the solution Q3 Whar is the mass % (m/w % ) of 1.0 mole of NaCl dissolved in 141.5g of water? The molar mass of NaCI is 23.0 35.5 58.5g Therefore the total solution is the 58.5g of NaCl plus the 141.5g of H,0 200.0 g of sohution and the mass %=58.5 g NaC/ 200 g solution x 100 0.293x 100 29.3 % 04-What is the volume % % ) of lquid fertilizer when 10 ml. is added to 250ml of water? The total volume of solution is 10.ml 250 ml -260 ml. The wv%- 10. ml/ 260 ml. x 100-3.8% os -A hand cream contains 60 mg of aloe vera per 300 ml. Of solurion. What is the my% 60wg-0.06g and hus my%-0.06g/300 ml x 100-0.02% In calculations of solute or solution, the percemt concentration is often used as a conversion factor. XCH2-fa gardener needs 50 gallons of dilated liquid fertilicer (see Q4 above) to fertilize the grass and plants in the yard how much o fthe undiluted fertiliz er must he buy? [Note that 50. gallons 200 qt, 200g x0.946 Liqt189L ar 190L (2 SF) dilted fertilizer S Molarity and Dilution -Molarity is the moles of solute in 1 liter (L) of solution. The units of molarity are moles liter, and are used in coaversion factors to solve for moles of solute or volume of solution. In dilution, the amount of solute does not change, but the volume of solvent increases and the solute concemtration decreases. Cv.-CV2or MVM;V Q7-Ifthe salution formed in Q3 above is diluted to a total valume of IL, 11'lwt is the NaCmolarity? Since the solution aiready contains 1.0 mole of NaCL and is diluted to a a toal volme of IL the molarity is exactly 1.0 M NaC Q8-What is the molarity of a solution comtaining 59.5g KBr dissolved in 250ml of solution? The molar mass of KBr is 39.1 g+ 79.9 g - 119.0g there/are 59.5g xI inole/119.0g-0.500 moles 0.500 moles KBr /0.250 L-2.00moles/ IL-2.00 M KBr. Q9-What volume of a 2.93% (ml l ) NaCl solution is prepared bv dluting 100. nil Of 29.3% solution: V2-V, x C/c-100.ml x (293 % / 2.93% ) - 100. ml (10.0)-1.00 L 6 Solutions in Chemical Reactions -We use the volume and molarity of a solution to determine the moles of the substance in solution. If the mass or solution volume and molarity of the substances in a reaction are known, a balanced equation can now peovide the quantities or concentrations of any of the other substances in the reaction. XCH3 How many L af0.125M BaC is needed to react with 0.65L of 0.320 M Na, SO, solation? 7 Properties of Solutions -Colloids contain particles that do not settle out, will pass through filters, but not pass through semipermeable membranes (such as cellular membranes). Suspensions are very large particles that settle out of solution In osmosis, solvent (water) passes through a semipemeable (allows passage of certain substances. while blocking others) membrane from the solution of a lower solute concentration to a solute of higher concentration (atempting to balance the concentrations on each side of the membrane). Osmotic pressure is the pressure that prevents any further flow of water imo the concentrated solution. The greater the # of particles dissolved in the water, the higher the osmotic pressure. If a pressure greaten than the osmotic pressure is applied, the flow will reverse, sending water from the more concentrated to the more dilute side. This process is known as reverse osmosis, sometimes used to purify salt water Because the cell membranes in biological systems are semipermeable, osmosis is an important peocess in biological systems. Key Words: Isotonic -A solution that has the same osmotic pressure as that of sed blood cells in the body. Hypotenic -A solution that has a lower osmotic pressure than the red blood cells (RBC ) of the body. A RBC will swell and may burst (hemolyze) in a hypotonic solution. Hypertenic -A solution that has a higher osmotic pressure than the RBCs of the body. A RBC will shrink (crenates) in a hypertonic solution Dialysis-A process whese water and small particles pass throagh a semipermeable membrane, typically to clean out contaminants (which will not pass throagh the membrane), such as in the blood stream.