Chapter 1 Multiple Choice Questions

. Which of these properties is proportional to the area of a given surface?

Surface excess entropy

Specific surface energy

Surface strain

Surface tension

Surface stress

. Which of the following statements is necessarily true when measuring surface stress relative to the principal stress axes on any given surface?

The normal stress components are zero

The normal stress components are equal

The normal and shear stresses are equal

The shear stress components are maximised

The shear stress components are zero

. A Wilhelmy plate, of negligible thickness and with lateral dimension 1.0 cm, is partially immersed in warm olive oil (surface tension 0.031 J.m^-2). After correction for buoyancy effects, the increase in apparent weight of the plate is 0.60 mN. Which of the following contact angles between plate and liquid is most consistent with these results?

0⁰

15⁰

30⁰

45⁰

60⁰

. An air-filled bubble, of diameter 1.6 cm, is formed by a thin film of soapy water whose surface tension is 0.050 J.m^-2. By how much will the air pressure inside the bubble exceed that of the surrounding air?

0.100 mbar

0.125 mbar

0.175 mbar

0.225 mbar

0.250 mbar

. The saturated vapour pressure above a curved liquid surface should exceed that of the same liquid's flat surface by a factor that…

Decreases logarithmically with increasing curvature

Increases logarithmically with increasing temperature

Decreases linearly with increasing temperature

Increases linearly with increasing curvature

Increases exponentially with increasing reciprocal temperature

. In the low-concentration regime, the specific surface energy of a certain liquid varies linearly with the bulk concentration of a given surfactant at some fixed temperature and pressure. Which of these statements may be inferred from the Gibbs isotherm?

The surface excess of the surfactant varies quadratically with its bulk concentration

The surface excess of the surfactant is precisely zero

The surface excess of the surfactant is independent of its bulk concentration

The surface excess of the surfactant varies logarithmically with its bulk concentration

The surface excess of the surfactant varies linearly with its bulk concentration

. The relative coverage of a certain species on some given solid surface is measured to be 0.50 at a pressure of 7.5 × 10^-8 mbar. Assuming Langmuirian behaviour, what relative coverage would be expected at a pressure of 2.5 × 10^-7 mbar?

0.57

0.67

0.77

0.87

0.97

. The relative coverage of a certain species on some given solid surface is measured to be 0.33 at a pressure of 6.66 × 10^-8 mbar, rising to 0.50 at a pressure of 1.25 × 10^-7 mbar. Assuming that adsorption occurs via a precursor state, which of the following would be the best estimate for the Kisliuk parameter?

0.25

0.33

0.50

0.67

0.75

. Adsorption of a certain species on some given solid surface is found to conform closely to the Brunauer-Emmett-Teller isotherm, and it is believed that a relative coverage of unity is achieved when the gas-phase pressure of that species is precisely one quarter of its saturated vapour pressure. What must be the value of the parameter c in the expression for the isotherm?

6

7

8

9

10

. The Clausius-Clapeyron equation permits estimation of adsorption heat given which type of data?

Temperature/pressure pairs consistent with a single fixed surface coverage

Surface stress/strain pairs consistent with a single fixed pressure

Surface stress/strain pairs with a single fixed coverage

Coverage/temperature pairs consistent with a single fixed pressure

Pressure/coverage pairs consistent with a single fixed temperature

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