Nitrogen

Question 1

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

Answer 1

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

Question 2

some uses of N

Answer 2

• 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

Question 3

stability and lack of reactivity of nitrogen?

Answer 3

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.

Question 4

mention as many N compounds and ions as possible

Answer 4

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

Question 5

obtain N in industry

Answer 5

fractional distillation of liquid air

Question 6

characteristics of ammonia

Answer 6

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

Question 7

ammonia burning in O2 (no catalyst)

Answer 7

NH3 + O2—> N2 + H2O

Question 8

ammonia passed over Pt catalyst, reaction between Nh3 and O2

Answer 8

gives NO and H2O

Question 9

manufacture of ammonia; name of process, conditions and catalyst

Answer 9

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

Question 10

overvew of haber process

Answer 10

-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

Question 11

prep of ammonia in lab

Answer 11

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

Question 12

precipitating metal hydroxides

Answer 12

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

Question 13

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

Answer 13

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+

Question 14

ammonia with a stronger reducing agent such as Na

Answer 14

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

Question 15

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

Answer 15

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

Question 16

heat decomposition of ammonium salts ; ammonium carbonate, ammonium chloride

Answer 16

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

Question 17

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

Answer 17

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

Question 18

production of nitrogen from ammoinum nitrate III

Answer 18

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

Question 19

methods of prep for N2

Answer 19

• 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

Question 20

production of N2O

Answer 20

• 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

Question 21

nitrogen pentoxide N2O5 properties

Answer 21

unstable, decomposes to give NO2 nad O2

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

Question 22

nitrogen pentoxide N2O5 lab prep

Answer 22

dehydration of nitric V acid with phosphorus V oxide

HNO3 + P2O5 to give HPO3 and N2O5

Question 23

N2O5 with water

Answer 23

nitric V acid HNO3

Question 24

nitrogen dioxide properties

Answer 24

brown gas,
structure is a resonance hybrid
a mixed anhydride

Question 25

NO2 with water

Answer 25

HNO2 and HNO3 . shows it's a mixed anhydride

Question 26

decomposition of NO2; what is needed

Answer 26

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

Question 27

NO2 disproportionation with water or an alkali

Answer 27

water;;;; HNO2 nad HNO3 | alkali;;;; NaNO2 and NaNO3 and H2O

Question 28

making N2O4

Answer 28

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

Question 29

lab prep of NO2

Answer 29

- 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

Question 30

nitrogen monoxide NO properties

Answer 30

- --colourlesss gas that forms brown fumes with air | - --used to extinguish burning materials unless the flame i hot enough to decompose it

Question 31

how can NO decompsoe

Answer 31

using magnesium, or strongly burning Cu or red hot Cu

Question 32

lab prep of NO

Answer 32

copper with 50% nitric V aq acid | Cu + HNO3 ----> Cu(NO3)2 + 4H2O + NO

Question 33

name of manufacture of nitric V oxide

Answer 33

ostwald process

Question 34

properties of nitric V acid

Answer 34

``` 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 ```

Question 35

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

Answer 35

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

Question 36

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

Answer 36

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

Question 37

lab prep of HNO3

Answer 37

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

Question 38

colour of nitric acid liquid, and nitric acid vapour

Answer 38

liquid is colourless but the vapour is yellow/orange

Question 39

nitric III acid properties

Answer 39

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

Question 40

unstability of HNO2 at room temp. show decomposition reaction

Answer 40

HNO2 becomes HNO3 +H2O and NO | No can obtain O2 to form NO2

Question 41

nitric II acid as an oxidsing agent

Answer 41

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

Question 42

nitric III acid as a reducing agent

Answer 42

it is oxidised from HNO2 to HNO3 | since it reduces it can decolourise acidified permanganate, orange dichromate to green chromium and bromine water

Question 43

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

Answer 43

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.

Question 44

testing for nitrates and nitrites;; the brown ring test

Answer 44

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+.

Question 45

testing for ammonia

Answer 45

overall can use moist red litmus becoming blue | for specific test. forms white cloud of ammonium chloride with HCl.

Question 46

describe the reactions involved in the brown ring test

Answer 46

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+

Question 47

whcih are the only trihalides that can form with nitrogen?

Answer 47

NCl3 - yellow oil | NI3- black solid

Question 48

properties of hydrazine

Answer 48

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

Question 49

production of hydrazine

Answer 49

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

Question 50

some uses of hyrazine

Answer 50

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

Question 51

talk abou tfactors to take into consideration into the haber process

Answer 51

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