O Levels Chemistry (5070)•5070/12/M/J/20

Explanation
Comparing %N and %S by mass in fertilizers X and Y
Steps:
- Calculate %N in NH4NO3: (2×14)/80 = 35%; in (NH4)2SO4: (2×14)/132 ≈ 21.2%.
- For X (500 g each): total N = (500×0.35) + (500×0.212) ≈ 281 g (28.1%); %S from (NH4)2SO4 = (500×32/132) ≈ 12.1%.
- For Y: %N from NH4NO3 = 24.5%; %S from CaSO4 = (300×32/136) ≈ 7.1%.
- X has higher %N (28.1% > 24.5%) and higher %S (12.1% > 7.1%).
Why A is correct:
- Calculations show X provides more N from dual sources and more S from sulfate, exceeding Y's single-source N and lower S content.
Why the others are wrong:
- B: Y has lower %N than X.
- C: X has higher %S than Y.
- D: X has higher %N than Y.
Final answer: A
Topic: Relative masses of atoms and molecules
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