4liquids and solutions - tep-tepe, faculty of … hydrogen electrode figure 3 half standard hydrogen...

SC 123 Fundamental Chemistry Asst. Prof. Peerasak Paoprasert 1

Solution

Figure 10 Solutions.

Solubility


Figure 11 Hexane, water, and CCl4

Temperature and solubility of solid

Figure 12 Temperature and solubility of solid

Temperature and solubility of gas


Figure 13 Temperature and solubility of gas

Pressure and solubility of gas

Figure 14 Pressure and solubility of gas


Figure 15 kH of gases

Energy of solution


Figure 16 Energy of solution

Solution of ionic compounds


Table 1 Enthalpy of hydration of ions

Enthalpy of Hydration (KJ/mol)

Cations Anions

H+ -1130 F- -483

Li+ -580 Cl- -340

Na+ -444 Br- -309

Mg2+ -2003

Ca2+ -1557

Al3+ -2537

Practice

1. Calculate the energy of solution of MgCl2 with a lattice energy of 3250 kJ/mol

Types of solution


Units of solubility (concentration)

Practice

1. Calculate the concentrations of methanol (CH3OH) 50 g in water 1000 g in mass

fraction, mole fraction, molal, molar, and ppm


Colligative properties

1. Depression of vapor pressure

Figure 17 Depression of vapor pressure of solution

2. Boiling-point elevation

3. Freezing-point depression


Figure 18 Kb and Kf of some liquids

Figure 19 Red blood cells in normal solution (left), salt solution (middle), and pure water

(right)

4. Osmotic pressure


Figure 20 ความดันออสโมติก

Practice

1. Calculate the boiling point, freezing point, and osmotic pressure of a solution of

methanol (CH3OH) 50 g in water 1000 g

Colloid


Practice

1. Calculate the concentrations of glucose (molecular weight =180 g/mol) 90 g in water

1000 g in mass fraction, mole fraction, molal, molar, and ppt

2. Calculate the volume of 0.1 M HCl in human stomach to digest magnesium

hydroxide 500 mg. Molecular weight of magnesium hydroxide is 58.3 g/mol.

3. Calculate the freezing point, boiling point, and osmotic pressure of a solution of

ethylene glycol 478 g in water 3202 g. Molecular weight of ethylene glycol is 62.01 g


4. For a 5.86 M ethanol solution (C2H5OH) with a density of 0.927 g/mL, calculate the

concentration of this solution in molal.

5. A unknown solution with 18 g of unknown and 150 g of water has a boiling point of

100.34 ˚C. Calculate the molecular weight of the unknown.

6. A solution of protein 1.00x10-3 g and water 1.00 mL has an osmotic pressure of 1.12

torr at temperature of 25.0 ˚C. Calculate the molecular weight of this protein

SC123 Fundamental Chemistry Asst. Prof. Peerasak Paoprasert 1

Electrochemistry

Electrochemical reactions

Figure 1 Redox reaction between Zn and Cu2+


Oxidation number

Balance redox equations


Practice

1. Balance redox reactions

a. H2O2 + Fe2+ Fe3+ + H2O (in acidic solution)

b. CN- + MnO4- CNO- + MnO2 (in basic solution)


Electrochemical cell

Table 1 Comparison between galvanic cell and electrolyte cell

Galvanic cell Electrolyte cell


Figure 2 Comparison between galvanic cell and electrolyte cell

Cell diagram

Standard hydrogen electrode

Figure 3 Half standard hydrogen cell

Standard half cell potential, E0


Figure 4 Measurement of standard half cell potential


Figure 5 Reduction potential


Cell potential, Ecell

Practice

1. Calculate cell potential of

a. Zn and Cu2+

b. MnO2 and Cu

c. Fe2+ and Cl-


Nernst equation

Thermodynamics and electrochemistry


Figure 6 Relationship between ΔG0 and E0cell

Practice

1. Calculate the equilibrium constant of 2H2O(l) 2H2(g) + O2(g) with Gibbs

free energy = -237.2 kJ/mol

2. Determine whether or not the following reaction is spontaneous at 298 K

Co(s) + Fe2+(aq) Co2+(aq) + Fe(s) when [Co2+]=0.15 M and [Fe2+] =0.68 M

Faraday law


Practice

1. Calculate the amount of zinc generated at cathode for current of 2.0 A passing

through ZnSO4 solution for 20 minutes.

Examples of electrochemical cells in daily life

1. Battery

Figure 7 Batteries

2. Rust protection


Figure 8 Rust protection of metal pipeline

3. Metal coating

Figure 9 Metal coating

Practice

1. Balance the redox equations

a. CH3CH2OH + Cr2O72- CH3COOH + Cr3+ (in basic solution)

b. Mg + O2 Mg2+ + H2O (in acidic solution)


2. Calculate E0 for the reaction between mercury and (a) 1 M HCl and (b) 1 M HNO3.

Which acid oxidize Hg to Hg22+ under standard condition

3. Calculate equilibrium constant of Sn(s) + 2Cu2+(aq) Sn2+(aq) + 2Cu+(aq)

4. Calculate the change of Gibbs free energy of

2Au(s) + 3Ca2+(aq, 1 M) 2Au3+(aq, 1 M) + 3Ca(s)


5. A galvanic cell with cell potential of 0.54 V at 25 ˚C ถ้า [Zn2+]=1.0 M and PH2 = 1.0

atm. Calculate the concentration of H+

6. Is this reaction spontaneous at 25 0C when [Fe2+] = 0.60 M and [Cd2+] = 0.010 M?

Fe2+ (aq) + Cd (s) Fe (s) + Cd2+ (aq)

7. Calculate equilibrium constant at 25 0C

Fe2+ (aq) + 2Ag (s) Fe (s) + 2Ag+ (aq)

8. For an electrochemical reaction of Na2SO4, there is oxygen gas and hydrogen gas

generated at anode and cathode, respectively. Write the corresponding redox

equations.


9. What is the cell potential of an electrochemical cell with Cd electrode and 1.0 M

Cd(NO3)2 solution and Cr electrode and 1.0 M Cr(NO3)3?

Cd2+ (aq) + 2e- Cd (s) E0 = -0.40 V

Cr3+ (aq) + 3e- Cr (s) E0 = -0.74 V

10. Calculate the current required to make 3 g of gold from AuCl3 solution in 20 minutes.

SC123 Fundamental Chemistry Asst. Prof. Dr. Peerasak Paoprasert 1

Chemical thermodynamics


Heat, q


Practice

1. Calculate heat capacity of 10 g of water at room temperature

2. Calculate heat required to boil 10 g of water from 30 degree Celsius


The First Law of Thermodynamics


Practice

1. Calculate ∆U of the following reaction at 25 C: N2(g) + 3H2(g) → 2NH3(g)

∆H° = −350 kJ


Practice

1. Calculate the enthalpy of the following reaction

CH4(g) + 4F2(g) → CF4(g) + 4HF(g)

Given (C-H) = 413 kJ, (F-F) =159 kJ, (C-F) =489 kJ, (H-F) =567 kJ


Practice

1. Calculate enthalpy C(gr) + 1/2O2(g) → CO(g) when

CO(g) + 1/2O2(g) → CO2 (g) ∆H2 = -283kJ

C(gr) + O2(g) → CO2 (g) ∆H3 = -393kJ


Practice


1. Calculate ∆H°rxn at 25°C of CaCO3(s) → CaO(s) + CO2(g) when ΔH°f, of

CaO(s)=-50.6 kJ/mol, ΔH°f of CO2(g)= -393.5 kJ/mol, and ΔH°f of CaCO3 = -120

kJ/mol


Practice

1. Calculate ∆S°rxn at 25°C of CaCO3(s) → CaO(s) + CO2(g) when ∆S°CaO(s)=39.8

J/K, ∆S°CO2(g)=213.6 J/K, ∆S°CaCO3 = 92.9 J/K


Practice

1. Predict whether or not this reaction is spontaneous if its enthalpy and entropy are

100 kJ/mol and 550 J/K, respectively.

Practice

1. Calculate ∆U at 25 C of 2CO(g) + O2(g) → 2CO2(g) at 25 oC ∆H° =

−566 kJ

2. Calculate w, q, ∆U when 1 mol of liquid water is turned into gas at 100 oC and 1

atm. Density of water at100 oC = 9.583 × 10-3 kg.m-3 and latent heat of water vapor=

40.63 kJ mol-1


3. What is the heat capacity of 60 g of water?

4. When 500 g of water is heated from 10 C to 90 C, how much heat is involved? Is this

an endothermic or exothermic process?

5. Calculate ΔH° of C(s) + 2H2(g) → CH4(g).

Given

C(s) + O2(g) → CO2(g) ΔH° = -393 kJ

H2(g) + 1/2O2(g) → H2O(l) ΔH° = -285 kJ

CH4(g) + 2O2(g) → CO2(g) +2H2O(l) ΔH° = -890 kJ

6. Predict the sign of ∆S°rxn of the following reactions

a. Ag+(aq) + Cl¯(aq) → AgCl(s)

b. NH4Cl(s) → NH3(g) + HCl(g)

c. H2(g) + Br2(g) → 2HBr(g)

7. Calculate entropy of the following reactions

a. N2(g) + 3H2(g) → 2NH3(g)

b. H2(g) + Cl2(g) → 2HCl(g)

4liquids and solutions - tep-tepe, faculty of … hydrogen electrode figure 3 half standard hydrogen...

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