A potassic fertiliser sample contains 50% K2O (potash) by analysis. Which product is consistent with this K2O content under standard commercial specifications?
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Apotassium sulphate (K2SO4)
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Bpotassium chloride (KCl)
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Ca mixture of NaCl + KCl
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Dnone of these
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Epotassium nitrate (KNO3)
Answer
Correct Answer: potassium sulphate (K2SO4)
Explanation
Introduction / Context:Potassic fertilisers are often reported as % K2O (potash) equivalent. Recognising which commercial salts align with a given K2O analysis helps in selecting products for chloride-sensitive crops and in interpreting fertiliser labels across markets.
Given Data / Assumptions:
- K2SO4 (sulphate of potash, SOP) typically assays ~50–52% K2O.
- KCl (muriate of potash, MOP) typically assays ~60–62% K2O.
- Mixed salts (NaCl + KCl) do not have a fixed K2O content and usually indicate diluted potash.
Concept / Approach:Match the reported K2O percentage to standard assay values for common potassic products. A 50% K2O analysis aligns with potassium sulphate, which is preferred for chloride-sensitive crops such as tobacco, certain fruits, and potatoes.
Step-by-Step Solution:
Recall typical analyses: SOP ≈ 50% K2O; MOP ≈ 60% K2O.Compare to given value: 50% K2O → SOP.Exclude KCl due to higher assay; exclude generic mixtures lacking a standard 50% value.Select potassium sulphate (K2SO4).Verification / Alternative check:Product datasheets and fertiliser regulations list SOP at ~50% K2O and MOP at ~60% K2O, corroborating the identification.
Why Other Options Are Wrong:
- Potassium chloride: typically ~60–62% K2O.
- NaCl + KCl mixture: variable K2O; not a standard 50% grade.
- None of these and KNO3: KNO3 has ~46% K2O equivalent and significant nitrogen, not exactly 50%.
Common Pitfalls:Confusing K2O equivalent with elemental potassium percentage; labels conventionally use K2O equivalents.
Final Answer:potassium sulphate (K2SO4)