Deck 4: Physical Transformations

Question 1

The density of liquid carbon disulfide, CS₂, is 1293 kg m^-3. Calculate the change in the molar Gibbs energy of carbon disulfide when it is compressed by a change in pressure from 1.00 bar to 2.00 bar.

A) +17.0 kJ mol^-1
B) +77.3 J mol^-1
C) +5.89 J mol^-1
D) +76.1 J mol^-1

Answer 1

C

Question 2

The densities of white and red phosphorus are 1.823 and 2.340 g cm^-3 respectively. Calculate the change in the molar volume for the transformation of white into red phosphorus.

A) 5.990 m³ mol^-1
B) 5.990  10^-2 m³ mol^-1
C) 5.990  10^-6 m³ mol^-1
D) 5.990  10^-4 m³ mol^-1

Answer 2

C

Question 3

Calculate the change in the molar Gibbs energy of a perfect gas when it expands isothermally at a temperature of 25 °C from a molar volume of 1.00 dm³ to a molar volume of 10.0 dm³.

A) 479 J mol^-1
B) +5.71 kJ mol^-1
C) +2.48 kJ mol^-1
D) +208 J mol^-1

Answer 3

B

Question 4

The molar Gibbs energy of tribromomethane, CHBr₃, decreases by 4.44 kJ mol^-1 when the temperature is increased from 288 to 308 K. Determine the molar entropy of tribromomethane.

A) -222 J K^-1 mol^-1
B) 222 J K^-1 mol^-1
C) 0.222 J K^-1 mol^-1
D) 22.2 J K mol^-1

Question 5

The molar entropy of 1,3-dioxane, C₄H₈O₂, is 196.6 J K^-1 mol^-1. What is the change in the molar Gibbs energy of 1,3-dioxane when it is heated from 298 K to 323 K?

A) -3.93 kJ mol^-1
B) -9.83 kJ mol^-1
C) -196.6 kJ mol^-1
D) -63.5 kJ mol^-1

Question 6

The normal boiling temperature of benzene, C₆H₆, is 353.3 K, whilst the triple point occurs at a temperature of 278.5 K and pressure of 4813 Pa. Determine the average value for the enthalpy of vaporization of benzene over this range.

A) 33.3 kJ mol^-1
B) 4.01 kJ mol^-1
C) 30.7 kJ mol^-1
D) 57.1 kJ mol^-1

Question 7

The normal boiling temperature of liquid bromine, Br₂, is 332 K and the standard enthalpy of vaporization is 29.45 kJ mol^-1. Use the Clausius-Clapeyron equation to determine the vapour pressure of liquid bromine at a temperature of 298 K.

A) 0.300 bar
B) 1.01 bar
C) 3.42 bar
D) 0.296 bar

Question 8

The vapour pressure p of liquid diethyl ether, (C₂H₅)₂O, may be calculated for different temperatures T using the expression
Log (p/bar)=A-B/T
Where, for the temperature range 24 to 48 °C, A = 4.743 and B = 1466.30 K. What is the vapour pressure of liquid diethyl ether at 25 °C?

A) 1.01 bar
B) 4.74 bar
C) 0.175 bar
D) 0.668 bar

Question 9

Estimate the normal boiling temperature of propan-1-ol, C₃H₇OH, given that its vapour pressure is 2701 Pa at 298 K and 9129 Pa at 318 K.

A) 393 K
B) 323 K
C) 367 K
D) 420 K

Question 10

For the equilibrium
CaCO₃(s) ∏ CaO(s) + CO₂(g)
How many phases are present?

A) 1
B) 2
C) 3
D) The number of phases cannot be determined

Question 11

When 15.0 cm³ of benzene, C₆H₆, is added to 125 cm³ of water, H₂O, at 20°C, the final volume of the liquid mixture is 137 cm³. Calculate the partial molar volume of benzene in dilute aqueous solutions given that the density of benzene and of water are 0.879 g cm^-3 and 0.998 g cm^-3 respectively, and the partial molar volume of water is 17.8 cm³ mol^-1 at this temperature.

A) 88.9 cm³ mol^-1
B) 81.8 cm³ mol^-1
C) 14.6 cm³ mol^-1
D) 86.8 cm³ mol^-1

Question 12

Calculate the change in the chemical potential of a perfect gas when its partial pressure doubles at a temperature of 200°C.

A) +2.73 kJ mol^-1
B) +1.15 kJ mol^-1
C) +0.50 kJ mol^-1
D) +0.30 kJ mol^-1

Question 13

Determine the molar Gibbs energy of mixing for the formation of an equimolar mixture of two perfect gases at a temperature of 298 K.

A) -0.745 kJ mol^-1
B) -0.372 kJ mol^-1
C) 0
D) -1.72 kJ mol^-1

Question 14

An ideal solution is prepared by mixing 15.6 g of toluene, C₆H₅CH₃, and 136.2 g of butan-1-ol, C₄H₉OH at 25 °C. The vapour pressure of pure butan-1-ol is 885 Pa at this temperature. Calculate the partial pressure of butan-1-ol in the vapour above the mixture.

A) 885 Pa
B) 811 Pa
C) 74.6 Pa
D) 90.9 Pa

Question 15

The Henry's law constant for pentan-3-one, C₂H₅COC₂H₅, in aqueous solution may be expressed in terms of concentration as 19.6 mol dm^-3 kPa^-1. Calculate the vapour pressure of pentan-3-one above an aqueous solution that contains 5.23 g of pentan-3-one in 250 cm³ of solution.

A) 12.4 kPa
B) 51.0 kPa
C) 31.1 kPa
D) 3.00 kPa

Question 16

What partial pressure of hydrogen, H₂, is required above an aqueous solution in order to ensure that the concentration of hydrogen in the solution is 1.00 mmol dm^-3? The Henry's law constant for hydrogen is 7.78 10^-3 mol m^-3 kPa^-1.

A) 129 Pa
B) 12.9 kPa
C) 129 kPa
D) 129 MPa

Question 17

Estimate the change in the normal boiling temperature of an aqueous solution made by dissolving 12.6 g of phenol, C₆H₅OH, in 250 cm³ of water. The ebullioscopic constant of water is 0.51 K kg mol^-1.

A) +0.27 K
B) +0.068 K
C) -1.6 K
D) -0.65 K

Question 18

Calculate the mass of sodium chloride, NaCl, required to lower the freezing temperature of ice by 0.50 K. The cryoscopic constant of water is 1.86 K kg mol^-1.

A) 8.1 g per kg water
B) 58 g per kg water
C) 16 g per kg water
D) 0.27 g per kg water

Question 19

Use the following data for the osmotic pressures of solutions of different mass concentrations of an enzyme in water at 298 K to determine the molar mass of the enzyme.
$\begin{array}{llllll}c_{\mathrm{B}} /\left(\mathrm{g} \mathrm{dm}^{-3}\right) & 2.00 & 4.00 & 6.00 & 8.00 & 10.0 \\\Pi / \mathrm{Pa} & 46 & 124 & 236 & 380 & 558\end{array}$

A) 212 kg mol^-1
B) 102 kg mol^-1
C) 121 kg mol^-1
D) 169 kg mol^-1

Question 20

At a temperature of 214 K, carbon disulfide, CS₂, and acetone, CH₃COCH₃, are not fully miscible and, instead, form separate liquid phases with mole fractions of carbon disulfide of 0.403 and 0.833. Use the lever rule to calculate the relative amounts of the two phases when 10.0 g of carbon disulfide and 10.0 g of acetone are mixed together at this temperature.

A) 13.8:1
B) 2.08:1
C) 1.31:1
D) 14.8:1