Video: GCSE Chemistry Higher Tier Pack 1 • Paper 2 • Question 8

GCSE Chemistry Higher Tier Pack 1 • Paper 2 • Question 8


Video Transcript

Phosphorus is a key nutrient for growing plants. Ammonium phosphate is a common source of phosphorus in NPK fertilizers. Complete the word equation for the reaction used to produce ammonium phosphate. Blank plus blank react to form ammonium phosphate.

As this is a word equation, we only need to find the chemical names of the components required to react to produce ammonium phosphate. You should recall that in order to produce sulfates, you use sulfuric acid. So what do we use in order to produce phosphates? Phosphoric acid.

And now, we have one part of the word equation complete. Now, we need to work out what reacts to produce ammonium. The answer is ammonia. We know this because an acid and a base react to produce a salt. Ammonium phosphate is a salt. Phosphoric acid is obviously an acid and the base that produces ammonium ions is ammonia.

So the complete word equation for the reaction used to produce ammonium phosphate is ammonia plus phosphoric acid react to form ammonium phosphate.

Tomato plants produce more fruit when grown in soil with a high potassium content. Explain why NPK values are useful to farmers seeking to maximize tomato yields.

The first thing we need to do is deconstruct the name NPK. Using your periodic table, you can see that the letters N, P, and K refer to nitrogen, phosphorus, and potassium. Remember that potassium is one of those unusual elements whose symbol doesn’t quite match up to its name.

So we now know that a fertilizer’s potassium content would be referred to in its NPK value. So a farmer might find these NPK values useful because a high K value would indicate that it’s good for growing tomatoes. NPK fertilizers are formulations with different percentages of nitrogen, phosphorus, and potassium, which are indicated by their NPK values. Recall that formulations are used for mixtures prepared according to a recipe. A farmer could maximize tomato yields by choosing fertilizers with high K values, high potassium.

Figure one shows how the worldwide use of ammonia per person and global mortality rate vary between 1961 and 1990. Explain the relationship between ammonia use and global mortality rate shown in Figure one.

There need to be two parts to this answer. The first is to describe the relationship between one factor and another. The second is to describe the reason why there is that relationship. The relationship is the easy part. We can see that as ammonia use increases, global mortality decreases. Now, let’s look at the reason why.

As we saw in a previous question, ammonia is used to make fertilizers. Fertilizers are in turn used to increase food production. And broadly speaking, the more food there is, the less death there is from malnutrition. So as ammonia use per person increases, the global mortality rate decreases.

Ammonia is used in the production of fertilizers, which increase the yield of food crops. Increasing use of ammonia reduces global mortality because more food is available per person, lowering rates of malnutrition.

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