10. Answer any two of the parts (a), (b) and (c) - Leaving Cert Chemistry - Question 10 - 2011

The type of catalyst responsible for the increased rate of reaction is known as a heterogeneous catalyst. It provides a surface on which the reactants can adsorb, lowering the activation energy required for the reaction.

1. The reactants adsorb onto the surface of the platinum catalyst, forming activated complexes. This allows for better orientation and concentration of reactants at the reaction site.

2. By lowering the activation energy, the catalyst speeds up the reaction, as the energies required for the bonds to break and form new bonds are reduced.

3. During the reaction, the catalyst remains unchanged and can continuously facilitate the reaction without being consumed.

A reaction profile diagram should consist of two curves: one for the uncatalyzed reaction, showing a higher energy barrier (activation energy) and one for the catalyzed reaction, showing a lower activation energy. The x-axis represents the reaction progress while the y-axis represents energy.

• Label the maximum energy point as the ‘activation energy’ for each reaction.
• Indicate the energy of the reactants and products on each curve.

The balanced chemical equation for the fermentation of glucose (C₆H₁₂O₆) to produce ethanol (C₂H₅OH) and carbon dioxide (CO₂) is:

$C₆H₁₂O₆ \rightarrow 2C₂H₅OH + 2CO₂$

The primary metabolite of ethanol in the human liver is acetaldehyde (C₂H₄O).

1. First, calculate the total volume of ethanol in the wine:

   • Volume of wine = 2 glasses × 175 ml/glass = 350 ml
   • Ethanol content = 12.5% (v/v)
   • Volume of ethanol = 350 ml × 0.125 = 43.75 ml
   • Density of ethanol = 0.8 g/ml
   • Mass of ethanol = 43.75 ml × 0.8 g/ml = 35 g

2. The rate of processing ethanol in a woman is 5.3 g/hour.

3. Time taken to metabolize ethanol = Total mass of ethanol / Rate of processing

   • Time = 35 g / 5.3 g/hour ≈ 6.6 hours.

1. If 90% of the ethanol is distributed in the woman's body fluids:

   • Ethanol distributed = 35 g × 0.90 = 31.5 g

2. Considering her total body fluid volume is 28 litres (or 28,000 ml):

   • Concentration in grams per 100 ml = (31.5 g / 28,000 ml) × 100 ml = 0.1125 g/100 ml.