Question

Chapter 13: Homework 13.1: The Solution Process 1. (13.16 Brown) Indicate the principal type of solute-solvent interaction in each of the following solutions and rank the solutions from weakest to strongest interaction: KCI in water b. CH, Cl, in benzene (CH) c. Methanol (CH,OH) in water a. 2. (13.22 Brown) The enthalpy of solution of KBr in water is about +198 kl/mol. Nevertheless, the solubility of KBr in water is relatively high. Why does the solution process occur even though it is endothermic? More book problems: 15 13.2 and 13.3:Saturated Solutions; Factors Affecting Solubility 3. (13.26 Brown) By referring to Figure 13.18, determine the mass of each of the following salts required to form a saturated solution in 250 g of water at 30°C a. KClO, b. Pb(NO) c. Ce,(SO.). 4. (13.34 Brown) Which of the following in each pair is likely to be more soluble in water: a. Cyclohexane (CH) or Glucose (CH20.) fig 13.12 b. Propionic acid (CH,CH,COOH) or sodium propionate (CH,CH,COONa) C.HCl or ethyl chloride (CH,CH,CI) 5. (13.37) The Henry's law constant for helium gas in water at 30.0°C is 3.7x10*M/atm and the constant for N, at 30.0*C is 6.0x10*M/atm. If the two gases are each present at 1.5 atm pressure, calculate the solubility of each gas. More book problems: 23, 25, 27, 29, 31, 33, 35; sample exercises 13.1, 13.2 13.4: Concentrations of Solutions 6. (13.40 Brown) What is the mass percentage of iodine (V) in a solution containing 0.035 mol l in 125 g of CCI? b. Seawater contains 0.0079 g Sr per kilogram of water. What is the concentration of Sr? measured in ppm? 1

Answer 1

(a) KCl is an ionic compound. It completely dissociates in water and results in ionic dipole interaction. It is considered one of the strogest interaction in which the dipole moment of a covalent compound,here water is changed due to the presence of ions.

(b) Between CH₂Cl₂ and benzene, the force that is acting is dipole Induced dipole force in which CH₂Cl₂ being polar in nature induces dipole moment in non-polar benzene. It is the weakest intermolecular force.

(c) Methanol in water has hydrogen bonding. It is one of the strongest interaction but not as strong as ionic dipole interaction.

So, The strongest force order is as follows.

ionic dipole interaction> hydrogen bonding> dipole induced dipole.

.H-W H ㅈ polar Dipole Non-polar Induced Dipole H -8 +8 S +8 co --H. CH U 2+2 oto HT "con-dipole interaction Depole Induced Dipole interaction. CH, CO H Hydrogen bonding

(2) Eventhough the enthalpy of solution of KBr in water is +198 KJ/mol, still the reaction proceeds. This is because the randomness or disorder increases due to the dissolving process. When a system gets increased in randomness, its spontaneity increases and hence entropy. So, the overall reaction proceeds as free energy decreases due to increase in entropy.

G

G= AH - TAS

where H is the enthalpy of solution

S is the entropy of the solution due to dissociation of KCl that increases the disorder.