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Chemistry > Ammonia > Flashcards

Ammonia Flashcards

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1
Q

Joseph priestly??

A

prepared ammonia by heating slaked lime. he called it alkaline air.

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2
Q

Claude Berthelot??

A

studied chemical properties of the gas

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3
Q

Davy??

A

established basic composition

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4
Q

lab prep of ammonia (using ammonium salts)

A

ammonium salt (NH4Cl) with an alkali (Ca(OH)2) , releasing CaCl2, H20 and NH3.

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5
Q

why is NH4NO3 not used in lab prep

A

explosive and decomposes

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6
Q

how and why is ammonia collected

A

downward displacement of air
1. lighter than air
2. highly soluble in water

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7
Q

why is more weight of alkali used in prep using ammonium salts

A

to counteract the loss by sublimation of NH4Cl on heating in solid state

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8
Q

why is Ca(OH)2 used in lab prep

A

cheap and not deliquescent

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9
Q

why is flask kept inclined in lab prep

A

so that water vapour may not trickle down and crack the hot flask

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10
Q

drying agent used for ammonia

A

quicklime

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11
Q

V.D of ammonia

A

8.5

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12
Q

lab prep of ammonia(metal nitrides)

A

Mg3N2 with warm water, releasing Mg(OH)2 and NH3

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13
Q

precaution of lab prep using metal nitrides

A

thistle funnel should dip below level of water

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14
Q

why is lab prep using metal nitride rarely used?

A

nitrides are expensive

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15
Q

what is the process of manufacture of ammonia called?

A

Haber’s process

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16
Q

Haber’s process

A

Nitrogen and hydrogen combine in a ratio of 1:3. 2 vols of ammonia is released.

17
Q

conditions of haber’s process

A

reversible, exothermic(22,400 cals), decrease in volume
temp: 450-500 degrees
pressure: 200-900 atmos.
catalyst: Fe/Mo

18
Q

precaution in haber’s process

A

CO, CO2, H2S poisons the catalyst, so mixture must be free of them

19
Q

how is ammonia in haber’s process condensed

A

mixture of NH3, and residual nitrogen and hydrogen is allowed to expand suddenly under high pressure, through a small nozzle into a region of low pressure.

20
Q

how is nitrogen of haber’s process obtained?

A

fractional distillation of air

21
Q

Le Chatelier’s principle

A

if a reaction is exothermic, it is favoured by lowering the temperature

22
Q

methods of seperation of ammonia from uncombined nitrogen and hydrogen in haber’s process

A
  1. liquefaction- it condenses at -33 degrees, at 8 atmos. p
  2. dissolving in water- 1 vol. of water dissolves 702 vols. of ammonia, at 20 degrees and 1 atmos. p
23
Q

physical properties of ammonia

A

colourless, strong pungent odour, slight alkaline taste
non poisonous, affects respiratory system

24
Q

freezing point and boiling point of ammonia

A

freezes: -77.7 degrees
boils: -33.5 degrees

25
Q

chemical properties of ammonia

A

neither combustible, nor a supporter of combustion
burns in oxygen and undergoes catalytic oxidation

26
Q

when is ammonia neutral to dry litmus

A

perfectly dry ammonia OR ammonia in liquefied form

27
Q

what is liquor ammonia

A

an aqueous solution of ammonia in water. it is prepared by dissolving ammonia gas in water using funnel arrangement

28
Q

why is ammonia basic?

A

aqueous solution of ammonia is alkaline and acts as a weak base, since it undergoes partial dissociation in aq. soln. to give hydroxyl ions in low concentration

29
Q

what happens when excess ammonia is passed through aqueous salt solutions

A

it precipitates hydroxides of metals from the solution of their salts

30
Q

why is ammonium hydroxide used in qualitative analysis for identifying positive cations

A

it reacts with metallic salt solutions to give insoluble precipitates of respective metallic hydroxides. precipitates vary in colour and solubility in excess NH4OH

31
Q

reducing nature of ammonia

A

reduces metallic oxides and chlorine

32
Q

what happens when ammonia reacts with excess chlorine

A

HCl is formed, along with explosive yellow liquid Nitrogen Trichloride

33
Q

how to prepare nitrogen from unstable ammonium nitrite

A

first prepare NH4NO2 by mixing NH4Cl with NaNO2. The ammonium nitrite decomposes into water and nitrogen

34
Q

nessler’s reagent

A

potassium mercuric iodide (turns pale brown in ammonia; brown precipitate is formed in excess)

35
Q

industrial uses of ammonia

A

source of hydrogen and nitric acid, explosives, urea, dyes and drugs, baking soda, washing soda, artificial silk, fertilizers

36
Q

uses of liquor ammonia

A
  1. emulsifies and dissolves fats, grease, removes oil stains
  2. cleans windows and porcelain
37
Q

uses of liquid ammonia

A

used as refrigerant, since
1. highly volatile and high latent heat of evaporation
2. easily liquefies under pressure, at low temperatures
therefore, when liquid ammonia evaporates, it absorbs a lot of heat from the surroundings and reduces the temperature

38
Q
A

Chemistry (11 decks)

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