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 = 1.0, N = 14) A 18% B 42% C 51% D 82% (b) The reaction between hydrogen and nitrogen is exothermic. Figure 13 shows the reaction profile of this exothermic reaction. energy reactants Q R products P S time Figure 13 (i) Which arrow represents the activation energy for the reaction? A arrow P B arrow Q C arrow R D arrow S (c) Ammonia, NH₃, and silicon dioxide, SiO₂, are both compounds that are made of two non-metallic elements. Ammonia has a boiling point of -33°C. Silicon dioxide has a boiling point of 2230°C. Explain why the boiling points of ammonia and silicon dioxide are so different.

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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

What is the percentage by mass of nitrogen in ammonia, NH₃?

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Answer

To find the percentage by mass of nitrogen in ammonia (NH₃), we first calculate the molar mass of NH₃.

The molar mass of nitrogen (N) is 14 g/mol.
The molar mass of hydrogen (H) is 1 g/mol, and there are three hydrogen atoms in ammonia.

Thus, the molar mass of NH₃ is calculated as:

$\text{Molar mass of NH₃} = (1 \times 1) + (1 \times 14) = 14 + 3 = 17 \text{ g/mol}$

Next, we calculate the percentage by mass of nitrogen:

$\text{Percentage by mass of N} = \left( \frac{\text{mass of N}}{\text{molar mass of NH₃}} \right) \times 100 = \left( \frac{14}{17} \right) \times 100 \approx 82\%$

Therefore, the answer is D 82%.

Step 2

Which arrow represents the activation energy for the reaction?

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Answer

The activation energy is represented by arrow R. This is the energy required to initiate the reaction, which can be identified as the energy difference between the reactants and the peak of the energy profile.

Step 3

Explain why the boiling points of ammonia and silicon dioxide are so different.

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Answer

Ammonia (NH₃) and silicon dioxide (SiO₂) have significantly different boiling points due to the nature of their intermolecular forces.

Intermolecular Forces in NH₃: Ammonia has hydrogen bonding, which is a strong type of dipole-dipole interaction. This occurs because of the significant electronegativity difference between nitrogen and hydrogen, allowing for strong interactions between molecules.
Intermolecular Forces in SiO₂: In contrast, silicon dioxide has a giant covalent structure. The atoms are held together by strong covalent bonds in a network structure, requiring a considerable amount of energy to break these bonds. Hence, the boiling point is extremely high.

In summary, NH₃ requires a lower amount of energy to overcome its hydrogen bonds, while SiO₂'s covalent network requires much more energy to break its bonds, leading to a significantly higher boiling point.

8 Ammonia can be produced from the reaction of hydrogen with nitrogen - Edexcel - GCSE Chemistry - Question 8 - 2023 - Paper 2

Worked Solution & Example Answer:8 Ammonia can be produced from the reaction of hydrogen with nitrogen - Edexcel - GCSE Chemistry - Question 8 - 2023 - Paper 2

What is the percentage by mass of nitrogen in ammonia, NH₃?

Which arrow represents the activation energy for the reaction?

Explain why the boiling points of ammonia and silicon dioxide are so different.

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