Sublimation temperature of dry ice (solid CO2) is ____________ °C?

Related Mcqs:

1. The wet bulb temperature is lower in dry air than in wet air at the same temperature. A dry bulb thermometer registers a higher temperature than a wet bulb thermometer except at ______________ percent relative humidity ?

   A. 0
   B. 100
   C. 50
   D. None of these

2. Choose the condition that must be specified in order to liquify CO2 (triple point for CO2 is – 57°C and 5.2 atm) ?

   A. Pressure must be kept below 5.2 atm
   B. Temperature must be kept above – 57°C
   C. Pressure must be kept below 5.2 atm. and temperature must be kept above 57°C
   D. Pressure and temperature must be kept below 5.2 atm. and – 57°C respectively

3. Consider the reaction, C + O2 ⇌ CO2; ΔH = – 94 kcal. What will be the value of ΔH for the reaction CO2 → C + O2 ?

   A. -94 kcal
   B. +94 kcal
   C. > 94 kcal
   D. < -94 kcal

4. Specific ____________ does not change during a phase change (e.g. sublimation, melting, vaporisation etc.)?

   A. Entropy
   B. Internal energy
   C. Enthalpy
   D. Gibbs free energy

5. “Dry ice” is________________?

   A. Moisture free ice
   B. Solid helium
   C. Solid carbon dioxide
   D. None of these

6. The combustion equations of carbon and carbon monoxide are as follows: C + O2 = CO2, ΔH = – 394 kJ/kg .mole CO + ½ O2 = CO2, ΔH = – 284.5 kJ/kg. mole. The heat of formation of CO is _____________ kJ/kg. mole?

   A. -109.5
   B. +109.5
   C. +180
   D. +100

7. Assuming that CO2 obeys perfect gas law, calculate the density of CO2 (in kg/m3) at 263°C and 2 atm ?

   A. 1
   B. 2
   C. 3
   D. 4

8. ____________ does not change during phase transformation processes like sublimation, melting & vaporisation?

   A. Entropy
   B. Gibbs free energy
   C. Internal energy
   D. All (A), B. & (C)

9. The molar composition of a gas is 10% H2, 10% O2, 30% CO2 and balance H2O. If 50% H2O condenses, the final mole percent of H2 in the gas on a dry basis will be_______________?

   A. 10%
   B. 5%
   C. 18.18%
   D. 20%

10. Joule-Thomson co-efficient which is defined as, η = (∂T/∂P)H = 1/Cp (∂H/∂T)P, changes sign at a temperature known as inversion temperature. The value of Joule-Thomson co-efficient at inversion temperature is ___________________?

    A. 0
    B. ∞
    C. +ve
    D. -ve