CHE+104+Chapter+13 - CHE 104 Chapter 13 Dr Mark Shuman Solutions A solution is a homogeneous mixture of two or more substances If I look at any

# CHE+104+Chapter+13 - CHE 104 Chapter 13 Dr Mark Shuman...

This preview shows page 1 - 15 out of 47 pages.

CHE 104 Chapter 13 Dr. Mark Shuman Solutions A solution is a homogeneous mixture of two or more substances. If I look at any microscopic portion of the solution, it will have the same composition as any other portion. A solution contains a solvent and one or more solutes. The solvent determines the state of the solution. If the solvent is a gas, the solution is a gas. If the solvent is a liquid, the solution is a liquid. If the solvent is a solid, the solution is a solid. Solutions (cont.) The solvent can be a gas, a liquid or a solid. The solute(s) can be gaseous, liquid or solid. Solutions (cont.) It is necessary to specify the solution composition. i.e. we must specify the relative amounts of solvent and solute in a solution. There are many ways to specify solution composition Molarity (M) Molality (c m ) Mole fraction ( ) Mass % And others Molarity (M) Molarity of a solute, A • M A = n soluteA /V solution “moles of solute per liter of solution” Solution volume typically depends on temperature so molarity should be specified for a given temperature. Molality (c m ) Molality of a solute, A – c mA = n soluteA /kg of solvent “moles of solute per kilogram of solvent” Moles of solute and mass of solvent are temperature independent so molality is temperature independent. Mole Fraction ( ) Mole Fraction of a solute, A A = n soluteA /n total here n total = total moles of solution. Moles are temperature independent so mole fraction is temperature independent. Mass Percent Mass % of a solute, A – % A = (mass A /mass solution ) * 100 Mass is temperature independent so mass % is temperature independent. Problem Assume you add 1.2 kg of ethylene glycol, HOCH 2 CH 2 OH, as an antifreeze to 4.0 kg of water in the radiator of your car. What are the mole fraction, molality and weight percent of the ethylene glycol? Problem You dissolve 1.0 mol of urea, H 2 NCONH 2 , in 270 g of water. What are the mole fraction and molality of the urea? Problem Suppose you dissolve 2.56 g of succinic acid, C 2 H 4 (CO 2 H) 2 , in 500. mL of water. Calculate the molality, mole fraction and weight percent of acid in the solution. Problem What mass of Na 2 CO 3 must you add to 125 g of water to prepare 0.200 m (molal) Na 2 CO 3 ?What is the mole fraction of Na 2 CO 3 in the resulting solution? Problem Concentrated sulfuric acid has a density of 1.84 g/mL and is 95% by weight H 2 SO 4 . What are the molality and molarity of this solution? Solubility If a solute is soluble in a solvent at any composition. The solute and solvent are said to be miscible . If a solute is not soluble in a solvent at any composition. The solute is said to be insoluble in that solvent.  #### You've reached the end of your free preview.

Want to read all 47 pages?

• Spring '08
• SHUMAN
• • •  