General Chemistry Answers

Given the ΔH° and ΔS°, calculate the G° values for the following reactions and indicate whether the reaction is spontaneous at standard conditions. If a reaction is not spontaneous, state what may be done to make the reaction spontaneous.

H° (kJ)

a. C (graphite) + 2 H2(g) ➡️ CH4(g) -74.9

b. CH3CH3(g) ➡️ H2(g) + C2H4(g) +137

c. N2(g) + 2 H2(g) ➡️ N2H2(L) +50

S°(kJ)

a. C (graphite) + 2 H2(g) ➡️ CH4(g)

+186.3

b. CH3CH3(g) ➡️ H2(g) + C2H4(g)

+121

c. N2(g) + 2 H2(g) ➡️ N2H2(L)

-331

Determine the pH of the buffer solution produced by the reaction of 5 mL 0.1 M KOH and 30 mL 0.1 M CH3COOH . The pKa of acetic acid is 4.76.

Find the pH of a solution produced by the reaction of 250 mL 0.1 M NaOH and 150 mL 0.03

M acetic CH3COOH Note that the pKa of acetic acid is 4.76.

Write the oxidation half-reaction and reduction half-reaction, and shorthand electrochemical notation for the following.

1. Mg+H^+ -> Mg^ 2+ +H 2

2. KI + Cl2 -> KCl + I2

3. Cr^ + +Sn^ 4+ Cr^ 3+ +Sn^ 2+

4. 3 Hg^ 2+ +2 Fe (s) 3 Hg 2 +2 Fe^ 3+

5. 2 As (n) + 3 Cl₂ (g) → 2 AsCla

6. NaBr + Cl₂ ⇒ NaCl + Br₂

7. F*e_{2}*O_{3} + CO -> Fe + C*O_{2}

8. CO + I_{2}*O_{5} -> C*O_{2} + I_{2}

2 Fe^ 3+ (aq) +Sn^ 2+ 2 Fe^ 2+ +Sn^ 4+ (aq)

10. Chlorine gas oxidises Fe2+ ions to Fe³+ ions. In the process, chlorine is reduced to chloride ions.

The following practice problems are prepared for you to polish and enrich your understanding in determining the oxidizing state of elements and further widen your understanding about the differences between an oxidizing agent and a reducing agent.

Assign oxidation state to the underlined element.

1) Cl₂

2) SO₂

3) K₂0₂

4) Cr₂07-²

5) Na₂O₂

6) Na₂S₂O3

7) NaN3

8) CH4

9) Fe₂O3

10) MnO₂

Why is the mass of the vinegar sample measures instead of its volume?

3.The heat of fusion of water is 6.01 kl/mol.The heat capacity of liquid water is 75.3 J/mol-K.The conversion of 50.0g of ice at 0.00°C to liquid water at 22.0°C requires _______ kj of heat.

A work of 657 J is done on a system that releases 434 J of heat. What is the energy change in the system?

An unknown fluid, of mass 0.952 is ignited in a 4-liter bomb calorimeter. Both the liquid inside the calorimeter and the calorimeter itself increased in temperature by 3.914K. Previously, the same calorimeter was calibrated using 1.951 grams of benzoic acid and both the water and the calorimeter increased in temperature by 8.209K. Assume that the density of the water inside the calorimeter is not temperature-dependent. Heat of combustion for benzoic acid is 3226kJ per gram.

a.Find the heat of combustion of the fluid.

b.Which compound releases more heat, the unknown fluid or benzoic acid?

Arrange the following species in order of (a) increasing ionic radius, and (b) increasing ionization energy: O2-, F-, Na+, Mg2+. Explain your answer in terms of nuclear charge and charge of ions.