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8 Ammonia can be produced from the reaction of hydrogen with nitrogen - Edexcel - GCSE Chemistry - Question 8 - 2023 - Paper 2
Question 8
8 Ammonia can be produced from the reaction of hydrogen with nitrogen. (a) What is the percentage by mass of nitrogen in ammonia, NH₃? (relative atomic masses: H =... show full transcript
Worked Solution & Example Answer:8 Ammonia can be produced from the reaction of hydrogen with nitrogen - Edexcel - GCSE Chemistry - Question 8 - 2023 - Paper 2
Step 1
(a) What is the percentage by mass of nitrogen in ammonia, NH₃?
Answer
To determine the percentage by mass of nitrogen in ammonia (NH₃), we first need to calculate the molar mass of ammonia:
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The atomic mass of hydrogen (H) is 1.0 g/mol, and there are 3 hydrogen atoms in NH₃, which contributes:
3 × 1.0 g/mol = 3.0 g/mol
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The atomic mass of nitrogen (N) is 14 g/mol.
Thus, the total molar mass of NH₃ is:
Next, we calculate the percentage by mass of nitrogen:
ext{Percentage of nitrogen} = rac{ ext{mass of N}}{ ext{mass of NH₃}} imes 100 = rac{14.0}{17.0} imes 100 \approx 82\%
Therefore, the answer is D 82%.
Step 2
(b)(i) Which arrow represents the activation energy for the reaction?
Answer
In the reaction profile shown in Figure 13, the activation energy is represented by the difference in energy between the reactants and the peak of the curve. This is depicted by arrow R, indicating the energy barrier that must be overcome for the reaction to occur. Thus, the answer is C arrow R.
Step 3
(c) Explain why the boiling points of ammonia and silicon dioxide are so different.
Answer
The boiling point differences between ammonia (NH₃) and silicon dioxide (SiO₂) can be attributed to the types of intermolecular forces present in each compound.
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Intermolecular Forces in NH₃: Ammonia exhibits hydrogen bonding due to the presence of a nitrogen atom bonded to hydrogen atoms. While hydrogen bonds are relatively strong compared to other van der Waals forces, they are weaker than the bonds present in silicon dioxide.
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Intermolecular Forces in SiO₂: Silicon dioxide forms a covalent network structure, meaning that it consists of a large number of atoms bonded together throughout the solid lattice. This results in extremely strong covalent bonds, making it require much more energy to break these bonds and transition to the gaseous state.
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Conclusion: Hence, ammonia has a much lower boiling point of -33°C, while silicon dioxide’s strong covalent bonds lead to a boiling point of 2230°C. The stark contrast in boiling points is a reflection of the different types of bonding and intermolecular forces at play.