## General, Organic, and Biological Chemistry: Structures of Life (5th Edition)

Published by Pearson

# Chapter 9 - Solutions - 9.6 Properties of Solutions - Questions and Problems - Page 360: 9.75

#### Answer

a. Freezing point = - 2.53 $^o C$ b. Freezing point = - 15.6 $^o C$ c. Freezing point = - 5.54 $^o C$

#### Work Step by Step

a. 1. Calculate the $\Delta T_f$ 1 mole of particles = 1.86 $^o C$ $CH_3OH$ is a nonelectrolyte: 1 mole $CH_3OH$ = 1 mole particles $$1.36 \space moles \space CH_3OH \times \frac{1 \space mole \space particles}{1 \space mole \space CH_3OH} \times \frac{1.86 \space ^o C}{1 \space mole \space particles} = 2.53 \space ^oC$$ 2. The freezing point of water is $0$ $^o C$, calculate the freezing point of the solution. $$T_{solution} = T_{water} - \Delta T_f$$ $$T_{solution} = 0 \space ^oC - 2.53 \space ^o C = -2.53 \space ^o C$$ b. 1. Find the molar mass for this compound: $C_3H_8O_2$ : ( 1.008 $\times$ 8 )+ ( 12.01 $\times$ 3 )+ ( 16.00 $\times$ 2 )= 76.09 g/mol 2. Calculate the $\Delta T_f$ 1 mole of particles = 1.86 $^o C$ $C_3H_8O_2$ is a nonelectrolyte: 1 mole $C_3H_8O_2$ = 1 mole particles $$640. \space g \space C_3H_8O_2 \times \frac{1 \space mole C_3H_8O_2}{76.09 \space g \space C_3H_8O_2} \times \frac{1 \space mole \space particles}{1 \space mole \space C_3H_8O_2} \times \frac{1.86 \space ^o C}{1 \space mole \space particles} = 15.6 \space ^oC$$ 3. The freezing point of water is $0$ $^o C$, calculate the freezing point of the solution. $$T_{solution} = T_{water} - \Delta T_f$$ $$T_{solution} = 0 \space ^oC - 15.6 \space ^o C = -15.6 \space ^o C$$ c. 1. Find the molar mass for this compound: $KCl$ : ( 35.45 $\times$ 1 )+ ( 39.10 $\times$ 1 )= 74.55 g/mol 2. Calculate the $\Delta T_f$ 1 mole of particles = 1.86 $^o C$ $KCl$ is an electrolyte that produces 2 ions: 1 mole $KCl$ = 2 moles particles $$111 \space g \space KCl \times \frac{1 \space mole KCl}{74.55 \space g \space KCl} \times \frac{2 \space mole s \space particles}{1 \space mole \space KCl} \times \frac{1.86 \space ^o C}{1 \space mole \space particles} = 5.54 \space ^oC$$ 3. The freezing point of water is $0$ $^o C$, calculate the freezing point of the solution. $$T_{solution} = T_{water} - \Delta T_f$$ $$T_{solution} = 0 \space ^oC - 5.54 \space ^o C = -5.54 \space ^o C$$

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