Exam 3 Practice

Which of the following reactions will have a positive value of ΔS?

 

I. Pb(s) + Cl₂(g) → PbCl₂(s)

II. 2H₂S(g) + 3O₂(g) → 2H₂O(g) + 2SO₂(g)

III. K₂SO₄(s) → 2K⁺(aq) + SO₄^2-(aq)

• III only

• I and III

• II only

• II and III

The enthalpy of vaporization of carbon tetrachloride (CCl₄) is 30.0 kJ/mol at its boiling point (77.0°C) (the liquid is in equilibrium with the vapor). Determine ΔS_sys, ΔS_surr, and ΔS_univ when 1.00 mol of carbon tetrachloride is vaporized at 77.0°C and 1.00 atm.

ΔS_{sys   _______________}

 J/K·mol

ΔS_{surr  _______________}

 J/K·mol

ΔS_{univ  _______________}

 J/K·mol

Tags

NGSS.HS-PS3-4

The standard entropy change, ΔS°(reaction) J/(K·mol), for the formation of SF₆(g) from the elements at 298.15 K is given below.

S(s) + 3 F₂(g) → SF₆(g) ΔS° = -348.7 J/(K·mol)

Calculate the standard molar entropy of SF₆(g) given that S°[S(s)] = 32.1 J/(K·mol) and S°[F₂(g)] = 202.8 J/(K·mol).

• -988.6 J/K*mol

• +291.8 J/K*mol

• -291.8 J/K*mol

• -113.23 J/K*mol

• +113.8 J/K* mol

For the reaction,

 

Fe₂O₃ (s) + 3 H₂(g)  2 Fe(s) + 3 H₂O(g), with
ΔG° = 63 kJ and ΔH° = 100 kJ at 25 °C.

 

Which of the following is completely true about the relationship between ΔG and T for this reaction?

 

• A. ΔG < 0 when T > 810 K 

• B. ΔG > 0 when T > 810 K

• C. ΔG < 0 when T > 0.8 K

• D. ΔG < 0 when T < 800 K 

• E. ΔG < 0 when T < 0.8 K

Calculate the value of ΔG° (in kJ) for the following reaction,

SiO₂(g) + 4HCl(g)  SiCl₄(g) + 2H₂O(g),

using the values of ΔG°_f (in kJ/mol) given below.

 

ΔG°_f [SiO₂(g)] = -86.                

ΔG°_f [HCl(g)] = -9.                           

ΔG°_f[SiCl₄(g)] = -62.

ΔG°_f [H₂O(g)] = -24.

Tags

NGSS.HS-PS1-4

At a temperature of 298K, a certain reaction has ΔG° = +29.4 kJ/mol and ΔH° = +80.4 kJ/mol. This reaction is predicted to become spontaneous at a temperature of ________

The standard free energy for a reaction is ΔG° = - 33.0 kJ. At 25°C the equilibrium constant for this reaction ,
K_p =

What is the overall cell reaction for the galvanic cell given in shorthand below?

Pt(s) ∣ H₂(g) ∣ H⁺(aq) ∣∣ Cl₂(g) ∣ Cl^-(aq) ∣ Pt(s)

• Pt(s) + H₂(g) + Cl^-(aq) → Pt(s) + 2 H⁺(aq) + 2 Cl₂(g)

• 2 H⁺(aq) + 2 Cl₂(g) → 2 HCl(aq)

• H₂(g) + Cl₂(g) → 2 H⁺(aq) + 2 Cl^-(aq)

• None of the other choices is correct.

Tags

NGSS.HS-PS1-7

If a constant current of 1.50  10⁸ A is passed through graphite electrodes into a molten mixture of aluminum oxide and cryolite for 4.00 hour, what mass of aluminum can be produced?

2Al₂O₃ + 3C → 4Al + 3CO₂

When a solution containing M(NO₃)₂ of an unknown metal M is electrolyzed, it takes 74.1 s for a current of 2.00 A to to plate out 0.0863 g of the metal. The metal is

• Mo

• Rh

• Cd

• Zn

• Cu