Chemistry Answers

What is the percent by volume of ethanol in a solution that contains 45mL of ethanol dissolved in 125mL of water?

2. If a sample of helium gas has a volume of 120 mL and a pressure of 850 mm Hg, what is the new

volume if the pressure is changed to 425 mm Hg ?

How many milliliters of a 6.75 M NaOH solution would be needed to prepare 575 mL of a 3.01 M solution?

For a certain process at 127°C, ΔG = -16.20 kJ and ΔH = -17.0 kJ. What is the entropy change for this process at this temperature? Express your answer in the form, ΔS = ____________________ J/K.

Calculate ΔG⁰ at 298 K for the reaction below.

Fe₂O₃(s) + 13CO(g) > 2Fe(CO)₅(g) + 3CO₂(g)

ΔH⁰_f (kJ/mol) -824.2 -110.5 -733.8 -393.5

S⁰ (J/mol•K) 87.4 197.6 445.2 213.6

Calculate the ΔG⁰_f at 298 K for the PbCI₂(s) from the following information. ΔG⁰ for the reactions below is -58.4 kJ at 298 K.

PbS(s) + 2HCI(g) > PbCI₂(s) + H₂S(g)

ΔG⁰_f (kJ/mol) 97.82 149.0 0 -228.6

Calculate the Standard Gibbs free energy change for the following reaction at 25 degree celcius.

CaCO₃ + 2HCI(g) > CaCI₂(s) + CO₂(g) + H₂O(I)

ΔG⁰_f (kJ/mol) 1129 -95.3 -750.2 -394.4 -237.2

Solve the following problems.

1. A voltaic cell is based on a Co2+ /Co half-cell and an AgCl/Ag half-cell.

a. What reaction occurs at the anode?

b. What is the standard cell potential?

2. Using the standard reduction potentials, calculate the standard emf for each of the following reactions:

a. 2Al3+ + 3Cd ⟶ 2Al + 3Cd2+

b. Cr + 2Cr3+⟶3Cr2+

c. H2 + I2 ⟶ 2H+ + 2I

Determine if each of the following redox reactions is spontaneous or not.

1. Cu + 2Ag+ ⟶ Cu2+ + 2Ag

2. Al3+ + Fe ⟶ Al + Fe2+

3. Zn + Ni2+ ⟶ Zn2+ + Ni

4. 3Pb + 2Au3+ ⟶ 3Pb2+ + 2Au

5. Hg + Pb2+⟶ Hg2+ + Pb

Determine if each of the following redox reactions is spontaneous or not.

1. Cu + 2Ag+ ⟶ Cu2+ + 2Ag

2. Al3+ + Fe ⟶ Al + Fe2+

3. Zn + Ni2+ ⟶ Zn2+ + Ni

4. 3Pb + 2Au3+ ⟶ 3Pb2+ + 2Au

5. Hg + Pb2+⟶ Hg2+ + Pb