Nitrogen Flashcards
how many bonds can N form and why is this so?
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
some uses of N
- 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
stability and lack of reactivity of nitrogen?
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.
mention as many N compounds and ions as possible
NO2- NO3- HNO2 HNO3 NO NO2 N2O N2O5 N2O4 N2O3 NH3 NH4+ NH2OH NH2NH2
obtain N in industry
fractional distillation of liquid air
characteristics of ammonia
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
ammonia burning in O2 (no catalyst)
NH3 + O2—> N2 + H2O
ammonia passed over Pt catalyst, reaction between Nh3 and O2
gives NO and H2O
manufacture of ammonia; name of process, conditions and catalyst
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
overvew of haber process
-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
prep of ammonia in lab
warm ammonium salt with alkali,, pass over CaO/soda lime to dry
precipitating metal hydroxides
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
addition of ammonia solution to copper sulfate solution. then excess ammonia
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+
ammonia with a stronger reducing agent such as Na
NH3 + Na to give NaNH2 and H2 (th eN remains in the same oxidation state)
ammonia acting as a reducing agent with CuO, Cl2 and ClO-
NH3 + CuO to give N2 + H2O + Cu
NH3 with Cl2 to give N2 + HCl
NH3 with ClO- to give N2 + Cl- and H2O
heat decomposition of ammonium salts ; ammonium carbonate, ammonium chloride
i) gives ammonia , CO2 and H2O
ii) gives NH3 and HCl
they are reversible reactions
thermal instability of NH4NO2(nitrate III) and NH4NO3 (nitrate V)
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
production of nitrogen from ammoinum nitrate III
using double decomposition. these are dissolved in water and heated gently
NaNO2 + NH4Cl —–> NaCl + N2 and H2O
methods of prep for N2
- 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
production of N2O
- 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
nitrogen pentoxide N2O5 properties
unstable, decomposes to give NO2 nad O2
it is the anhydride of nitric V acid (dehydration product)
nitrogen pentoxide N2O5 lab prep
dehydration of nitric V acid with phosphorus V oxide
HNO3 + P2O5 to give HPO3 and N2O5
N2O5 with water
nitric V acid HNO3
nitrogen dioxide properties
brown gas,
structure is a resonance hybrid
a mixed anhydride
NO2 with water
HNO2 and HNO3 . shows it’s a mixed anhydride
decomposition of NO2; what is needed
burning Mg or P, it will continue to burn since O2 is produced
NO2 disproportionation with water or an alkali
water;;;; HNO2 nad HNO3
alkali;;;; NaNO2 and NaNO3 and H2O
making N2O4
dimerisation of NO2. NO2 into N2O4 is exothermic so low temp and high pressure is preffered for NO2 to be produced
lab prep of NO2
- 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
nitrogen monoxide NO properties
- –colourlesss gas that forms brown fumes with air
- –used to extinguish burning materials unless the flame i hot enough to decompose it
how can NO decompsoe
using magnesium, or strongly burning Cu or red hot Cu
lab prep of NO
copper with 50% nitric V aq acid
Cu + HNO3 —-> Cu(NO3)2 + 4H2O + NO
name of manufacture of nitric V oxide
ostwald process
properties of nitric V acid
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
nitric V acid being an oxidising agent with i) Cu, ii)Mg
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
HNO3 being an oxidisng agent with non metals ;;; with P, S ,,H2S
P becomes P2O5 phosphoric V oxide
S becomes H2SO4
H2S becomes H2SO4 or S
lab prep of HNO3
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
colour of nitric acid liquid, and nitric acid vapour
liquid is colourless but the vapour is yellow/orange
nitric III acid properties
weak unstable monoprotic acid
pale blue liquid
can act as an oxidising agent
can also act as a reducing aeent
unstability of HNO2 at room temp. show decomposition reaction
HNO2 becomes HNO3 +H2O and NO
No can obtain O2 to form NO2
nitric II acid as an oxidsing agent
NO2- of the acid is reduced to NO. the other is oxidised
nitric III acid as a reducing agent
it is oxidised from HNO2 to HNO3
since it reduces it can decolourise acidified permanganate, orange dichromate to green chromium and bromine water
test ofr nitrates and nitrites;; using Devadra’s alloy
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.
testing for nitrates and nitrites;; the brown ring test
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+.
testing for ammonia
overall can use moist red litmus becoming blue
for specific test. forms white cloud of ammonium chloride with HCl.
describe the reactions involved in the brown ring test
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+
whcih are the only trihalides that can form with nitrogen?
NCl3 - yellow oil
NI3- black solid
properties of hydrazine
colourless, flammable liquid, ammonia like odour, highly toxic, dangerously unstable
production of hydrazine
oxidation of NH3 by H2O2 or NaOCl
NH3 +H2O2 N2H4 + H2O
NH3 + NaOCl N2H4 +NaCl +H2O
some uses of hyrazine
rocket fuel. catalysts cause it to decompose into NH3 and N2 or N2 and H2
talk abou tfactors to take into consideration into the haber process
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
