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Surface Chemistry — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistrySurface Chemistry3 Marks
Question
Consider the adsorption isotherms given alongside and interpret the variation in the extent of adsorption $\Big(\frac{\text{x}}{\text{m}}\Big)$ when:
  1.  
  1. Temperature increases at constant pressure.
  2. Pressure increases at constant temperature.
  1. Name the catalyst and the promoter used in Haber’s process for manufacture of ammonia.
✓

Answer

  1.  
  1. At constant pressure, extent of adsorption $\Big(\frac{\text{x}}{\text{m}}\Big)$decreases with increase in temperature as adsorption is an exothermic process.
  2. At constant temperature, first adsorption $\Big(\frac{\text{x}}{\text{m}}\Big)$increases with increase in pressure up to a particular pressure and then it remains constant.
At low pressure, $\Big(\frac{\text{x}}{\text{m}}\Big)=\text{kp}$

At intermediate range of pressure, $\Big(\frac{\text{x}}{\text{m}}\Big)=\text{kp}^\frac{1}{\text{n}}(\text{n}>1)$

At high pressure, $\Big(\frac{\text{x}}{\text{m}}\Big)=\text{k}$ (Independent of pressure)
  1. Finely divided iron is used as a catalyst and molybdenum is used as promoter.

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