(a) (i) Draw the abbreviated structural formula, in truncated form, of the compound that would be produced from the reaction of one molecule of glycerol with one molecule each of A, B and C .Circle and name the new functional group(s) produced. What type of reaction is represented by the reactions of A, B, and C with glycerol, and what other product is generated by these reactions?
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A CH3 -(CH2)7 -CH2 -C -OH
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B CH3- (CH2)15- CH2- C -OH
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C CH3- (CH2)7- CH= CH -(CH2)6- CH2- C- OH
Figure 4 Compounds, A, B and C. (ii) Explain, in terms of the type of molecule you have drawn, its chemical bonding and potential interaction with water, why the compound with the molecular structure you have drawn in part (a)(i) is not soluble in water. (
(b) Glycerol reacts with nitric acid (HNO3) to produce a colourless liquid, Compound D (Reaction 1). This reaction is undertaken in the presence of a catalyst (sulfuric acid, H2SO4).
C3 HO (l) + 3HNO3 (l) <=>C3 H3 (NO3 )3 (l) + 3H2 O(l) ΔH =− 364 kJ mol−1 (1)
Compound D
(i) State whether Reaction 1 is exo- or endothermic and draw a fully labelled diagram to show how the internal energy changes during the process represented by Reaction 1. Indicate the energy barrier for the reaction.
(ii) Explain the role of sulfuric acid in terms of the energy barrier of Reaction 1.
(iii) Reaction 1 is used commercially, but the vessel in which it is undertaken is cooled to maintain a steady temperature of 22 °C. Assuming Reaction 1 is reversible, as indicated, explain, in terms of Le Chatelier’s principle and the product yield, why this cooling is required.
(iv) When Reaction 1 is complete, Compound D can only be isolated once the acids have been removed. This is achieved by adding a strong base (sodium hydroxide, NaOH(aq)).
Explain what is meant by a strong base . Write balanced chemical equations, including state symbols, to illustrate (1) the reaction that occurs when solid sodium hydroxide is dissolved in water and (2) the reaction that occurs when sodium hydroxide solution is added to sulfuric acid. What type of reaction is represented by the equation you have written in (2)?
(c) Compound D decomposes rapidly to produce nitrogen, carbon dioxide, water vapour, oxygen and heat energy according to Reaction 2, with an energy change known as the enthalpy of decomposition. The temperature of this reaction can exceed 5000 °C.
4C3 H5 (NO3 )3 (l) = 12CO2 (g) + 10H2 O(g) + 6N2 (g) +O2 (g) + heat (2)
3533 22 22
Calculate the volume occupied by the gaseous products from the complete decomposition of 4 moles of Compound D, as shown in Reaction 2, when cooled to 25 °C and at atmospheric pressure.
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As you can see structural formulas cannot be drawn on the board because of spacing problems.
The fact you found this means you googled the question as well!
(a) (i) To draw the abbreviated structural formula of the compound produced from the reaction of glycerol with A, B, and C, we need to consider the reaction between glycerol and each compound individually.
Glycerol is C3H8O3, and let's denote the molecule produced by the reaction as D. The reaction between glycerol and A can be represented as:
C3H8O3 + A -> D
Similarly, the reactions between glycerol and B and C are:
C3H8O3 + B -> D
C3H8O3 + C -> D
To draw the abbreviated structural formula of D, we need to combine the molecular structures of A, B, and C with glycerol. Since the question does not provide the structures of A, B, and C, we cannot accurately draw the structure of D.
(ii) The new functional group(s) produced in the reaction of glycerol with A, B, and C are not given in the question. To determine the functional groups, you would need to know the structures of compounds A, B, and C.
The type of reaction represented by the reactions of A, B, and C with glycerol is also not provided in the question. To determine the type of reaction, you would need to know the reaction conditions and the chemical mechanisms involved.
(b) (i) The reaction between glycerol and nitric acid to produce compound D (C3H3(NO3)3) is exothermic because the enthalpy change (ΔH) is negative (-364 kJ mol-1). In an exothermic reaction, the internal energy decreases as heat is released to the surroundings.
In terms of the internal energy changes during the process represented by Reaction 1, you can draw a potential energy diagram. The diagram would show the reactants (glycerol and nitric acid) at a higher energy level, the transition state at the energy barrier, and the products (compound D and water) at a lower energy level. The energy barrier represents the activation energy required for the reaction to occur.
(ii) Sulfuric acid (H2SO4) acts as a catalyst in Reaction 1. A catalyst lowers the activation energy required for a reaction to proceed, increasing the rate of the reaction. By providing an alternative reaction pathway with lower activation energy, sulfuric acid facilitates the reaction between glycerol and nitric acid and allows the production of compound D.
(iii) Cooling the vessel in which Reaction 1 is undertaken is required to maintain a steady temperature of 22 °C. According to Le Chatelier's principle, when a system at equilibrium is disturbed by a change in temperature, pressure, or concentration, the system will shift to counteract the change.
In this case, cooling the vessel helps maintain a lower temperature, which favors the exothermic reaction (Reaction 1) and improves the yield of compound D. The reverse reaction, which is endothermic, would be less favored at lower temperatures.
(iv) Adding a strong base, such as sodium hydroxide (NaOH(aq)), helps remove the acids and isolate compound D.
A strong base is a substance that completely dissociates into ions when dissolved in water. In the case of sodium hydroxide, it dissociates into sodium ions (Na+) and hydroxide ions (OH-).
The chemical equation for the reaction when solid sodium hydroxide is dissolved in water is:
NaOH(s) + H2O(l) -> Na+(aq) + OH-(aq)
The reaction that occurs when sodium hydroxide solution is added to sulfuric acid can be represented as:
2NaOH(aq) + H2SO4(aq) -> Na2SO4(aq) + 2H2O(l)
This reaction is a neutralization reaction, where the base (sodium hydroxide) reacts with the acid (sulfuric acid) to form a salt (sodium sulfate) and water.
(c) To calculate the volume occupied by the gaseous products from the complete decomposition of 4 moles of Compound D (C3H5(NO3)3), we need to use the ideal gas law equation, PV = nRT.
Since the question does not specify the pressure or the value of R, it is not possible to calculate the volume accurately. To calculate the volume, you would need to know the pressure and temperature conditions.
The balanced chemical equation for the decomposition of Compound D (Reaction 2) is:
4C3H5(NO3)3(l) -> 12CO2(g) + 10H2O(g) + 6N2(g) + O2(g) + heat
The equation does not provide enough information to accurately calculate the volume without the given conditions.