A potassic fertiliser sample contains 50% K2O (potash) by analysis. Which product is consistent with this K2O content under standard commercial specifications?

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:

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)