Q: A galvanic cell is constructed using a Zn/Zn$$^{2+}$$ and Cu/Cu$$^{2+}$$ half-cell. The standard cell potential ($$E^ ext{cell}_ ext{std}) is 1.10 V. If $$the concentration of Zn$$^{2+} is 0.10 M $$and Cu$$^{2+} is 1.0 M at 25$$°C, what is the cell potential ($$E^ ext{cell}) $$using the Nernst equation? (Assume $$n = 2$$ and $$R = 8.314 J/$$mol·K, $$F = 96485 C/$$mol, $$T = 298 K)$$

$$E^ ext{cell} = 1.04\ \text{V}$$

Q: A reaction has $$\Delta G = -25\ \text{kJ/mol}$$ and $$E_ ext{cell} = 0.26\ \text{V}. $$Which equation relates these quantities?

$$\Delta G = -nFE_\text{cell}$$

Q: A reaction has $$K = 1.0 \times 10^5$ at 298 K. What is $$\Delta G$$ for this reaction? (R = 8.314$ J/mol·K)

$$\Delta G = -28.6\ \text{kJ/mol}$$

Question 1

A galvanic cell is constructed using a Zn/Zn$$^{2+}$$ and Cu/Cu$$^{2+}$$ half-cell. The standard cell potential ($$E^	ext{cell}_	ext{std}) is 1.10 V. If $$the concentration of Zn$$^{2+} is 0.10 M $$and Cu$$^{2+} is 1.0 M at 25$$°C, what is the cell potential ($$E^	ext{cell}) $$using the Nernst equation? (Assume $$n = 2$$ and $$R = 8.314 J/$$mol·K, $$F = 96485 C/$$mol, $$T = 298 K)$$

Accepted Answer

$$E^	ext{cell} = 1.04\ 	ext{V}$$

Question 2

The rate constant $$k$$ for a reaction increases from $$1.2 	imes 10$$^{-3}$$\ 	ext{s}^{-1} at 300 K to$$ $$4.8 	imes 10$$^{-3}$$\ 	ext{s}^{-1} at 320 K. $$Using the two-point Arrhenius equation, what is the activation energy ($$E_a) in kJ/$$mol? ($$R = 8.314 J/$$mol·K)

Accepted Answer

$$E_a = 34.6\ 	ext{kJ/mol}$$

Question 3

A buffer solution is prepared by mixing 0.50 mol of acetic acid ($$	ext{p}K_a = 4.76) $$and 0.30 mol of sodium acetate in 1.0 L of water. What is the pH of the solution using the Henderson-Hasselbalch equation?

Accepted Answer

$$	ext{pH} = 4.52$$

Question 4

The emission spectrum of hydrogen shows a line at $$486\ 	ext{nm}. $$Using the Rydberg equation, which electronic transition does this correspond to?

Accepted Answer

$$n=4 \rightarrow n=2$$

Question 5

Which equation correctly relates Gibbs Free Energy ($$\Delta G) to $$the equilibrium constant ($$K) at $$temperature $$T$$?

Accepted Answer

$$\Delta G = -RT \ln K$$

Question 6

A first-order reaction has a rate constant $$k = 0.693\ 	ext{hr}^{-1}. If $$the initial concentration is $$[A]_0 = 0.80\ 	ext{M}$$, what will $$[A] be $$after 2 hours? (Use the integrated rate law for first-order reactions)

Accepted Answer

$$[A] = 0.20\ 	ext{M}$$

Question 7

Which constant is defined as the number of particles in one mole of a substance?

Accepted Answer

Avogadro's number

Question 8

A reaction has $$\Delta G = -25\ 	ext{kJ/mol}$$ and $$E_	ext{cell} = 0.26\ 	ext{V}. $$Which equation relates these quantities?

Accepted Answer

$$\Delta G = -nFE_	ext{cell}$$

Question 9

Which equation is used to calculate the energy of a photon given its frequency ($$
u$$)?

Accepted Answer

$$E = h
u$$

Question 10

A second-order reaction has an initial concentration $$[A]_0 = 0.50\ 	ext{M}$$ and a rate constant $$k = 0.20\ 	ext{M}^{-1}	ext{s}^{-1}. $$What is the concentration of $$A$$ after 10 seconds? (Use the integrated rate law for second-order reactions)

Accepted Answer

$$[A] = 0.25\ 	ext{M}$$

Question 11

Which constant has the value $$6.022 	imes 10$$^{23}$$\ 	ext{mol}^{-1}$$?

Accepted Answer

Avogadro's number

Question 12

Which equation is used to calculate the energy change in a system where heat ($$q) $$and work ($$w) $$are exchanged?

Accepted Answer

$$\Delta U = q + w$$

Question 13

A medical device uses a redox reaction to generate electricity. If the device operates at $$E_	ext{cell} = 0.50\ 	ext{V}$$ and transfers 2 moles of electrons, how much work (in kJ) can be done? ($$F = 96485 C/$$mol)

Accepted Answer

$$-96.5\ 	ext{kJ}$$

Question 14

Which equation is used to relate the wavelength ($$\lambda) $$and frequency ($$
u) of $$light?

Accepted Answer

$$c = \lambda 
u$$

Question 15

Which constant is defined as $$6.626 	imes 10$$^{-34}$$\ 	ext{J}\cdot	ext{s}$$?

Accepted Answer

Planck's constant

Question 16

A reaction has $$K = 1.0 	imes 10^5$ at 298 K. What is $$\Delta G$$ for this reaction? (R = 8.314$ J/mol·K)

Accepted Answer

$$\Delta G = -28.6\ 	ext{kJ/mol}$$

Question 17

Which constant is defined as $$8.314\ 	ext{J/mol}\cdot	ext{K}$$?

Accepted Answer

Ideal gas constant

Question 18

Which constant is defined as $$3.00 	imes 10^8$\ 	ext{m/s}$$?

Accepted Answer

Speed of light

Question 19

Which constant is defined as $$96485\ 	ext{C/mol}$$?

Accepted Answer

Faraday's constant

Essential Equations and Constants in General Chemistry

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