Fertilisers are concentrated forms of plant nutrients
Which of the following ions do plants need for growth?
Tick one box.
| Cu2+ | |
| PO43– | |
| SO42- | |
| OH– |
Potassium nitrate is used as a fertiliser. The potassium ion has the formula K+ and the nitrate ion has the formula NO3–.
Give the formula for potassium nitrate.
What property must fertilisers have in order for plants to take up the ions through their roots.
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Fertilisers are used to promote plant growth.
Two fertilisers are ammonium phosphate, (NH4)3PO4, and calcium dihydrogenphosphate,Ca(H2PO4)2.
Describe a test to distinguish between these two fertilisers.
test ..................................................
result ..................................................
Many fertilisers are manufactured from ammonia.
Describe how ammonia is made in the Haber process. Give the essential conditions and an equation for the process.
State the essential plant nutrient not supplied by ammonium phosphate.
The soluble compound, calcium dihydrogenphosphate is made by heating the insoluble mineral rock phosphate, Ca3(PO4)2, with sulfuric acid.
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The Atacama desert in Chile has deposits of the salt sodium nitrate.
Very large amounts of this salt were exported to Europe for use as a fertiliser. After the introduction of the Haber process in 1913, this trade rapidly diminished.
5 marksThe equation for the decomposition of copper(II) nitrate is given below.
2Cu(NO3)2 → 2CuO + 4NO2 + O2
Copper(II) nitrate forms a series of hydrates with the formula Cu(NO3)2.xH2O.
All these hydrates decompose to form copper(II) oxide.
1 mole of Cu(NO3)2.xH2O forms 1 mole of CuO.
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Groundwater can contain fertilisers washed from fields. An example of a fertiliser that can be found is ammonium nitrate.
3 marksDrinking water extracted from rivers in agricultural areas often contain nitrates. The first legal standard for nitrate in drinking water was set in 1980. The current UK drinking water standard is 50 mg / dm3 to safeguard against cases of methaemoglobinaemia or blue baby syndrome.
Calculate the maximum mass in grams of nitrate that would be safe in a 240 cm3 glass of water. Give your answer to two significant figures.
An alternative fertiliser is ammonium phosphate.
3 marksPhosphates can be found in reservoirs from which drinking water is obtained. A maximum of 0.025 mg / dm3 of phosphate ions is allowed by water companies.
A sample of reservoir water has a concentration of 0.00014 mol / dm3.
Calculate the percentage of the maximum mass allowed of phosphate ions in the sample of reservoir water.
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Plants require three main elements for healthy growth which be provided by fertilisers.
Give the formulae of three ions used to make fertilisers which provide the three required elements.
Calcium nitrate is used as a fertiliser to help prevent blossom end rot in tomatoes which causes browning of the bottom of the fruit. It provides both calcium and nitrogen.
Write the formula for calcium nitrate.
2 marksUsing your answer to part (b) calculate the percentage by mass of nitrogen in calcium nitrate.
(Ar: Ca = 40, N = 14, O = 16)
Explain why salts from fertilisers end up in bodies in groundwater.
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