TOPIC

Ammonio

E ttttuhiple Choice Questions

Which method is least likely to produce ammonia gas?

A. heating ammonium sulfate with lithium hydroxideB. heating concentrated ammonium chlorideC. heating ammonium nitrate with dilute nitric acidD. heating a mixture of sodium nitrate, aluminium foil and aqueous sodium hydroxide

Diammonium hydrogen phosphate, (NH4)2HPO4, is a widely used fertiliser. Which of the followingsubstances could be added to this compound to produce a mixture that provides the three principalelements needed for plant growth?

A. ammonium sulfate

B. magnesium nitrate

C. ammonium phosphate

D. potassium chloride

In the Haber process, ammonia is separated from the hydrogen and nitrogen reactants byA. dissolving hydrogen and nitrogen in water.

B. passing the gaseous mixture through fused calcium chloride.C. passing the gaseous mixture through calcium oxide.D. cooling the gaseous mixture.

5. The flowchart below shows how a salt which is used as a fertiliser can be produced from three elementsA, B and C.

l.

2

4.

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Acompound of

AandBB salt

reaction withan acid

compound ofBandC

Cwater

Ammonia

3. Ammonia is manufactured by the Haber process using iron catalyst. Which of the following statementsis incorrect?

A. Nitrogen is reduced by hydrogen.

B. It is not possible to obtain a lO0 Vo yietd of ammonia.

C. A higher temperature will increase the yield of ammonia.D. The iron catalyst is used to increase the speed of the reaction.

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hydrogennitrogenA. oxygen

oxygen nitrogenB hydrogen

oxygenC. nitrogen hydrogen

oxygennitrogenD. hydrogen

7

6.

8.

What could be elements A, B and C?

In the Haber process for the manufacture of ammonia, which of the following statements are colrect?

I The catalyst used is a transition metal.

II Unreacted nitrogen and hydrogen are circulated back into the system.

m Both reactants are obtained from the fractional distillation of liquefied air.

IV The reaction is never complete and the yield achieved is only about I 0 - 15 7o .

A. I, II and III only

B. I, II and IV only

C. II, III and IV only

D. All of the above

A test-tube with a stopper is known to consist of at least one of the following gases

. nitrogen

. hydrogen

. ammonia

Tests were carried out and the results are shown below

Which of the following gases can be found inside the test-tube?

A. ammonia and hydrogen

B. nitrogen and ammonia

C. hydrogen only

D. ammonia only

A fertiliser containing ammonium sulfate and calcium carbonate is sometimes used by agricultural

farmers. Why is this fertiliser useful?

A. It provides nitrogen required for plant growth while reducing the acidity of the soil.

B. It provides all the essential nutrients required for plant growth.

C. It provides both nitrogen and carbon dioxide required for plant growth.

D. It helps to reduce excess acidity of the soil.

extinguishes with a 'pop'soundlighted splint

remains reddamp red litmus paper

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Element A Element B Element C

Test Observation

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9. The diagram below shows some of the important stages in the manufacture of ammonium sulfatefertiliser.

pipe 1 pipe2

pipe 5

pipe 3 pipe 4

From which of the connecting pipes would a major leak cause the highest increase in the pH of rain?

A. pipe 2 only

B. pipes I and 2 only

C. pipes 3 and 4 only

D. pipes 4 and 5 only

E Stn ctrrred Questions

1. Ammonia is an extremely useful chemical. It is made industrially by the Haber process.

(a) Write a balanced chemical equation with state symbols for the formation of ammonia.(b) State the sources ofnitrogen and hydrogen.

(c) What are the optimum conditions for the Haber process?

(d) A mixture of ammonia, nitrogen and hydrogen is obtained at the end of the reaction. Ammonia isthen separated from nitrogen and hydrogen by cooling down the mixture to -45 oC and changinggaseous ammonia into a liquid. Comment on the boiling points of ammonia and its reactants.

(e) It is known that the volumes of nitrogen and hydrogen are mixed in the ratio of I : 3. What is the

reason for doing so?

(f) If the above process is carried out in the school laboratory, state a method other than cooling that canbe used to separate ammonia from its reactants.

(g) The catalyst used in the Haber process is usually finely divided. Explain this requirement based onthe Collision Theory.

(h) An engineer explains that this reaction does not go towards 100 7o completion. An experiment was

carried out in the laboratory to confirm the engineer's claim. 1.00g of hydrogen gas was reactedwith excess nitrogen gas. At the end of the reaction, 1.00 dm3 of ammonia was formed and collected.What was the percentage yield of ammonia at room temperature and pressure?

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nitrogen andhydrogen ammonia

ammonlumsulfate

sulfur and

oxygensulfur dioxideand oxygen

sulfuricacid

Ammonia

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3.

Ammonia is used to make fertilisers which are extremely important in agriculture to improve crop

yield.

A new agricultural farmer went to a fertiliser factory to source for fertilisers as well as other substances

that will be able to help him increase his crop yield. The factory salesperson introduced the following

fertilisers, which come in 1 kg bags, to be added to the soil to improve the crop yield.

. ammonium nitrate, NH4NOT

. ammonium chloride, NH4C/

. diammonium sulfate, (NH4)2SO1

. diammonium hydrogen phosphate, (NH4)2HPO4

o urs&r (NHr)rCO

He explained that the above fertilisers are essential for plants because they provide nitrogen vital for

plants to make proteins necessary for growth and repair of plant cells.

(a) Show by calculation which one of these fertilisers is most suitable for the farmer. Show your working

and reasoning clearly.

(b) Write the chemical formulae of the ions present in diammonium hydrogen phosphate.

(c) (i) The salesperson also recommended that the farmer purchase calcium hydroxide as the farm

area is situated near industrial factories. Why was calcium hydroxide recommended?

(ii) The farmer was also advised by the salesperson not to add the above ammonium-based

fertilisers to the soil together with calcium hydroxide' Explain why.

(iii) Write the ionic equation for the reaction that takes place when calcium hydroxide is added to

ammonium nitrate.

(d) The farmer also leamed that fertilisers with the label NPK (for nitrogen, phosphorus and potassium)

on them is good for plants. Decide whether the following bags containing mixtures of compounds

are NPK fertilisers.

Bag A: contains ammonium chloride and potassium hydrogen phosphate

Bag B: contains sodium phosphate and potassium nitrate

Bag C: contains ammonium sulfate and potassium chloride

Bag D: contains potassium hydrogen sulfate and ammonium hydrogen phosphate

Solid urea, (NHrrCO is a very useful nitrogenous-based fertiliser and can be prepared by reacting

ammonia with carbon dioxide. Water is the other product from this reaction.

In an experimerfi,72.O dm3 of carbon dioxide is converted to urea at room temperature.

(a) Write the chemical equation, including the state symbols, for the formation of urea.

(b) Calculate the volume of ammonia reacted.

(c) Calculate the mass of urea formed.

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4. The graph below shows the yield of ammonia produced at different temperatures and pressures in the Haberprocess. Each curve represents a change of yield with changing pressure at a constant temperature.

yield ofammonnia I Vo

100

90

80

70

60

50

40

30

20

l0

0

200 "c

300'c

400'c

500.c

25 100 200 300 400

pressure / atm

500

Use the graph to answer the following questions.

(a) One factory operates at 400 "C and 200 atm. What is the yield of ammonia under these conditions?(b) (i) What is the effect on the rate of reaction by increasing the pressure of the reacting gases?

Explain with reference to the colliding particles.

(ii) What is the effect on the yield of ammonia by increasing the pressure of the reacting gases?

(iii) Give one disadvantage of carrying out the reaction under a higher pressure.

(c) What is the effect of increasing the temperature? Discuss.

(d) Explain why the yield of ammonia is never l00Vo.

(e) Write down the equations for both the forward and backward reactions.

(f) The reactants, hydrogen and nitrogen are not used up and are recycled back into the system. Givetwo reasons for doing so.

(g) Is the Haber process a redox reaction? Explain your answer using oxidation states.

Ammonia!,

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