Video Transcript
Which of the following combinations of chemicals would not make a complete NPK fertilizer? (A) D, E, and F; (B) B, C, and D; (C) B, E, and F; (D) C, E, and F; or (E) A, B, and E.
A fertilizer is a substance or a mixture of substances added to soil that provides plants with essential nutrients. An important type of fertilizer is an NPK fertilizer. N, P, and K are the atomic symbols for nitrogen, phosphorus, and potassium. So a complete NPK fertilizer is a fertilizer which contains all three elements. Many synthetic fertilizers contain nitrogen, phosphorus, and/or potassium in the form of various compounds.
We’ve been given six different compounds, and each contains at least one of these elements. We need to determine which combination of compounds would not make a complete NPK fertilizer. To start, we’ll need to know the chemical formula of each compound. Ammonium phosphate has the chemical formula (NH4)3PO4. We can see that this compound is a source of both nitrogen and phosphorus. Potassium nitrate has the chemical formula KNO3. This chemical is a source of both potassium and nitrogen. Both ammonium sulfate, (NH4)2SO4, and sodium nitrate, NaNO3, are sources of nitrogen. Potassium chloride, KCl, is a source of potassium, and sodium phosphate, Na3PO4, is a source of phosphorus.
Now that we know the element or elements that each chemical can provide, let’s evaluate the answer choices. The combination of chemicals D, E, and F would contain the elements nitrogen, phosphorus, and potassium. Thus, this combination is a complete NPK fertilizer, but we want to know which combination of chemicals would not make a complete NPK fertilizer. As such, we can eliminate answer choice (A).
The combination of chemicals B, C, and D would provide the elements nitrogen and potassium but not phosphorus. Thus, this combination of chemicals is not a complete NPK fertilizer and is likely the answer to this question. But just to be sure, let’s take a look at answer choices (C), (D), and (E).
The combination of chemicals B, E, and F would contain the elements nitrogen, phosphorus, and potassium. This is a complete NPK fertilizer, so answer choice (C) is not correct. The combination of chemicals C, E, and F would also contain nitrogen, phosphorus, and potassium. Thus, the combination of chemicals in answer choice (D) is a complete NPK fertilizer and is not the answer to this question. The combination of chemicals A, B, and E also contains nitrogen, phosphorus, and potassium. This is a complete NPK fertilizer. Thus, answer choice (E) cannot be the answer to this question.
So the combination of chemicals that would not make a complete NPK fertilizer is answer choice (B) B, C, and D.
