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This question is about the reaction between hydrogen sulfide (H₂S) and oxygen - AQA - GCSE Chemistry - Question 8 - 2021 - Paper 1
Question 8
This question is about the reaction between hydrogen sulfide (H₂S) and oxygen. The equation for the reaction is: 2 H₂S(g) + 3 O₂(g) → 2 H₂O(g) + 2 SO₂(g) 1. What ... show full transcript
Worked Solution & Example Answer:This question is about the reaction between hydrogen sulfide (H₂S) and oxygen - AQA - GCSE Chemistry - Question 8 - 2021 - Paper 1
Step 1
Step 2
Calculate the volume of oxygen required to react with 50 cm³ of hydrogen sulfide.
Answer
To find the volume of oxygen needed, we can use the stoichiometry from the balanced equation:
The reaction shows that 2 volumes of H₂S react with 3 volumes of O₂.
Thus, if 50 cm³ of H₂S is being used, we can set up a ratio:
egin{align*} rac{2 ext{ cm}^3 ext{ H₂S}}{3 ext{ cm}^3 ext{ O₂}} & = rac{50 ext{ cm}^3 ext{ H₂S}}{x ext{ cm}^3 ext{ O₂}} \
ext{Cross-multiply:}
\ 2x = 150 \ \ x = 75 ext{ cm}^3 ext{ O₂} ext{Therefore, the volume of oxygen required is 75 cm³.} \
Step 3
Complete Figure 6:
Answer
To complete Figure 6:
- Draw the profile line starting from the reactants’ energy level, rising to a peak (activation energy level), and then descending to the products’ energy level.
- Label the peak as 'Activation energy', which represents the minimum energy required for the reaction to occur.
- Label the difference in energy between the reactants and products as 'Overall energy change', indicating it is exothermic since the products are at a lower energy level.
Step 4
Calculate the bond energy X for the S=O bond.
Answer
To find the bond energy X for the S=O bond, we can use the following equations based on bond energies:
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Calculate the total energy needed to break bonds:
egin{align*} ext{Bonds broken} &= 4 imes (364) + 3 imes (498) \ &= 1456 + 1494 = 2950 ext{ kJ/mol} ext{(Energy to break existing bonds)} \ ext{Bonds formed} &= 2 imes (464) + 4 imes (X)\ = 928 + 4X \ ext{Energy released} &= 2950 + 1034 = 3984 ext{ kJ/mol} \ 3984 &= 928 + 4X \ 4X &= 3984 - 928 = 3056 \ X &= rac{3056}{4} = 764 ext{ kJ/mol} ext{ (thus bond energy X is 764 kJ/mol.)} \ ext{Alternatively, approach calculation can be verified:} \ (2984 - 1034) = 1856 + 4X\ (3984 = 1856 + 4X) 4X=2984
X = 532 kJ/mol \The bond energy for the S=O bond is X = 532 kJ/mol.