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Chemistry > Nitrogen > Flashcards

Nitrogen Flashcards

1
Q

how many bonds can N form and why is this so?

A

It can form 3 covalent bonds because it has 3 unpaired electrons at ground state since N has no d orbital it is unable to expand its covalency beyond 3

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2
Q

some uses of N

A
  • gaseous is used to create inert atmospheres for reactions in ; incandescent light bulbs
  • liquid N is a cryogenic liquid. mainly used as a refrigerant. also for cryopreservation of blood and cells,and for cryotherapy to remove cysts and warts
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3
Q

stability and lack of reactivity of nitrogen?

A

N is very stable and unreactive
due to very high bond enthalpy of diatomic N. the lack of reactivity is explained by the triple bond which is short and very strong.

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4
Q

mention as many N compounds and ions as possible

A

NO2- NO3- HNO2 HNO3 NO NO2 N2O N2O5 N2O4 N2O3 NH3 NH4+ NH2OH NH2NH2

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5
Q

obtain N in industry

A

fractional distillation of liquid air

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6
Q

characteristics of ammonia

A 
thermally stable 
less dense than air
pungent gas
weak lowry bronsted base
good monodentate ligand with Cu2+, Zn2+ and Ni2+
reducing agent
can act as a nucleophile
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7
Q

ammonia burning in O2 (no catalyst)

A

NH3 + O2—> N2 + H2O

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8
Q

ammonia passed over Pt catalyst, reaction between Nh3 and O2

A

gives NO and H2O

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9
Q

manufacture of ammonia; name of process, conditions and catalyst

A

haber process, 250 atm and 450 degrees, iron mixed with small amounts of promoters like K2O or Al2O3,,
some atmospheric carbon is also produced;; CO2 is regularly removed due to increasing partial pressures affecting yeild of NH3

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10
Q

overvew of haber process

A 
-obtain H2 and N2
purification of gases
heating of gases, then put in convertor
pressure and temp and catalyst
hot gas is cooled to -50
NH3 liquifies and collected
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11
Q

prep of ammonia in lab

A

warm ammonium salt with alkali,, pass over CaO/soda lime to dry

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12
Q

precipitating metal hydroxides

A

the OH- concentration in aq ammonia is usually enough to cause precitation of metal hydroxides. these metal hydroxides are amphoteric or can dissolve in excess strong alkali. eg Mg2+ + OH- to give Mg(OH)2

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13
Q

addition of ammonia solution to copper sulfate solution. then excess ammonia

A

pale blue precipitate of cu(OH)2 forms.

upon excess, the pp dissolves to form a deep blue soln of tetraamminecopperII ions [Cu(NH3)4]2+

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14
Q

ammonia with a stronger reducing agent such as Na

A

NH3 + Na to give NaNH2 and H2 (th eN remains in the same oxidation state)

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15
Q

ammonia acting as a reducing agent with CuO, Cl2 and ClO-

A

NH3 + CuO to give N2 + H2O + Cu
NH3 with Cl2 to give N2 + HCl
NH3 with ClO- to give N2 + Cl- and H2O

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16
Q

heat decomposition of ammonium salts ; ammonium carbonate, ammonium chloride

A

i) gives ammonia , CO2 and H2O
ii) gives NH3 and HCl
they are reversible reactions

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17
Q

thermal instability of NH4NO2(nitrate III) and NH4NO3 (nitrate V)

A

thsi occurs with ammonium salts of oxidising acids
the ammonia produces will be oxidised to N2 or an oxide of nitrogen
these 2 salts are explosive:
NH4NO2 —–> N2 and H2O
NH4NO3 —–> N2O and H2O

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18
Q

production of nitrogen from ammoinum nitrate III

A

using double decomposition. these are dissolved in water and heated gently
NaNO2 + NH4Cl —–> NaCl + N2 and H2O

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19
Q

methods of prep for N2

A
  • with ammonia acting as a reducing agent such as NH3 with Cuo or Cl2 or ClO-
  • heat decomposition of ammonium dichromate (red solid) to give Cr2O3, N2 and H2O
  • decomposition of ammonium nitrate III:: either directly or from prep and then decompsotiion of thesalt
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20
Q

production of N2O

A
  • heat together KNO3 and (NH4)2SO4 to produce ammonium nitrate V which will melt and decompose to form N2O, K2SO4 and H2O (heating ammonium nitrate V)
  • 4Mg+2NO3- + 10H+ ——> 4Mg2+ + N2O + 5H2O
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21
Q

nitrogen pentoxide N2O5 properties

A

unstable, decomposes to give NO2 nad O2

it is the anhydride of nitric V acid (dehydration product)

22
Q

nitrogen pentoxide N2O5 lab prep

A

dehydration of nitric V acid with phosphorus V oxide

HNO3 + P2O5 to give HPO3 and N2O5

23
Q

N2O5 with water

A

nitric V acid HNO3

24
Q

nitrogen dioxide properties

A

brown gas,
structure is a resonance hybrid
a mixed anhydride

25
Q

NO2 with water

A

HNO2 and HNO3 . shows it’s a mixed anhydride

26
Q

decomposition of NO2; what is needed

A

burning Mg or P, it will continue to burn since O2 is produced

27
Q

NO2 disproportionation with water or an alkali

A

water;;;; HNO2 nad HNO3

alkali;;;; NaNO2 and NaNO3 and H2O

28
Q

making N2O4

A

dimerisation of NO2. NO2 into N2O4 is exothermic so low temp and high pressure is preffered for NO2 to be produced

29
Q

lab prep of NO2

A
  • copper with conc HNO3 nitric V acid
    Cu + HNO3 to give NO2, Cu(NO3)2 and H2O
  • heat on anhydrous nitrate V salts (not group 1)
    lead II nitrate is usually used. the gases produced are poassed over a u tube immersed in a freezing mixture. NO2 liquifies and O2 goes out. PbO is preffered since it doesnt have water of crystallization

Pb(NO3)2 (s) heat PbO, NO2 and O2
YELLOW SOLID PbO

30
Q

nitrogen monoxide NO properties

A
  • –colourlesss gas that forms brown fumes with air

- –used to extinguish burning materials unless the flame i hot enough to decompose it

31
Q

how can NO decompsoe

A

using magnesium, or strongly burning Cu or red hot Cu

32
Q

lab prep of NO

A

copper with 50% nitric V aq acid

Cu + HNO3 —-> Cu(NO3)2 + 4H2O + NO

33
Q

name of manufacture of nitric V oxide

A

ostwald process

34
Q

properties of nitric V acid

A 
strong monoprotic acid
ionises completely to give nitrate ion
acid stuff;; neutralise alkalis, dissolve basic oxides and liberates CO2 from carbonates and hydrogencarbonates
oxidising agent 
nitrating agent
35
Q

nitric V acid being an oxidising agent with i) Cu, ii)Mg

A

50% HNO3;; gives Cu(NO3)2 H2O and NO
conc gives Cu(NO3)2, H2O and NO2

Ng + NO3- + H+ Mg2+ + NH4+ + H2O
Mg +NO3- +H+ Mg2+ + N2O and H2O

36
Q

HNO3 being an oxidisng agent with non metals ;;; with P, S ,,H2S

A

P becomes P2O5 phosphoric V oxide
S becomes H2SO4
H2S becomes H2SO4 or S

37
Q

lab prep of HNO3

A

involatile acid with nitrates
NaNO3 + H2SO4 —-> NaHSO4 +HNO3
cold water is poured over teh flask to cool the nitric acid vapors and form a liquid

38
Q

colour of nitric acid liquid, and nitric acid vapour

A

liquid is colourless but the vapour is yellow/orange

39
Q

nitric III acid properties

A

weak unstable monoprotic acid
pale blue liquid
can act as an oxidising agent
can also act as a reducing aeent

40
Q

unstability of HNO2 at room temp. show decomposition reaction

A

HNO2 becomes HNO3 +H2O and NO

No can obtain O2 to form NO2

41
Q

nitric II acid as an oxidsing agent

A

NO2- of the acid is reduced to NO. the other is oxidised

42
Q

nitric III acid as a reducing agent

A

it is oxidised from HNO2 to HNO3

since it reduces it can decolourise acidified permanganate, orange dichromate to green chromium and bromine water

43
Q

test ofr nitrates and nitrites;; using Devadra’s alloy

A

the sample is heated with alkali alone to remove any ammonium ions. Devarda’s alloy ( Zn, Cu, Al) is added to the mixture and heated again. any ammonia released shows the presence of NO3- or NO2-. they are being reduced to ammonia.

44
Q

testing for nitrates and nitrites;; the brown ring test

A

equal volumes of the soln being tested and acidified iron sulfate are mixed. the test tube is held inclined at 45degrees and conc H2SO4 is trickled fown the side of the test tube. the acid forms a seperate layer at the bottom of the test tube since its denser. if those ions are present a brown layer froms between the 2 layers. the brown is unstable comples [Fe(H2O)5NO]2+.

45
Q

testing for ammonia

A

overall can use moist red litmus becoming blue

for specific test. forms white cloud of ammonium chloride with HCl.

46
Q

describe the reactions involved in the brown ring test

A

example given with NO3-
1) reduction of nitate /nitrite to NO
Fe2+ +NO3- +4H+ Fe3+ +NO +2H2O

2) reaction between NO and remaining Fe2+
[Fe(H2O)6]2+ +NO [Fe(H2O)5(NO) ]2+ +H2O

upon mixing these layers the complex decomposes forming pale yellow soln of Fe3+

47
Q

whcih are the only trihalides that can form with nitrogen?

A

NCl3 - yellow oil

NI3- black solid

48
Q

properties of hydrazine

A

colourless, flammable liquid, ammonia like odour, highly toxic, dangerously unstable

49
Q

production of hydrazine

A

oxidation of NH3 by H2O2 or NaOCl
NH3 +H2O2 N2H4 + H2O
NH3 + NaOCl N2H4 +NaCl +H2O

50
Q

some uses of hyrazine

A

rocket fuel. catalysts cause it to decompose into NH3 and N2 or N2 and H2

51
Q

talk abou tfactors to take into consideration into the haber process

A

rate, yield and cost
pressure:
the higher teh pressure th more the yeild but also the greater the cost and the more maintenance needed for the equipment,, so compromise pressure of 200atm

temp: the lower , the more yield but that would lower the rate way too much and be uneconomical,,, so compromise temp of 450 degrees

Chemistry (11 decks)

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