CL1 - Nitrogen Chemistry

Question 1

Bonding in N2?

Answer 1

strong triple bond

Question 2

another name for ammonia - NH3

Answer 2

nitrogen hydride

Question 3

bonding in ammonia - NH3

Answer 3

3 bonding pairs + 1 lone pair

Question 4

Bonding in an ammonium ion - NH4+

Answer 4

3 bonding pairs (NH) + 1 dative covalent bond
BUT
once formed all bonds = equivalent –> ammonium ion has just a positive charge + no dative bond

Question 5

Appearance of gases:
NO
NO2
N2O

Answer 5

NO = colourless --> brown in NO2
NO2 = brown
N2O = colourless

Question 6

2 kinds of nitrate ions in nitrogen cycle

Answer 6

nitrate(III) = NO2-

nitrate(V) = NO3- (+5 oxidation state)

Question 7

how do you form NO2- and NO3-?

Answer 7

ADD OXYGEN TO AMMONIUM IONS

NH4+ + 1.5O2 —> NO2- + 2H+ + H2O

NO2- + 0.5O2 —> NO3-

Question 8

How to test for nitrate ions?

Answer 8

• NaOH + Devarda’s alloy (Cu/Al/Zn)
• add to test solution + gently heat
• Al = REDUCING AGENT
• if nitrate(V) - NH3- present –> AMMONIA gas produced

Question 9

Recognising if ammonia is produced?

Answer 9

sharp choking smell
red litmus –> blue
white fumes of ammonium chloride when comes into contact with hydrogen chloride gas fumes from conc. HCl

Question 10

Testing for ammonium ions - NH4+?

Answer 10

• NaOH + test solution
• gently heat
• ammonia produced

Question 11

Where do these gases come from?
NO
NO2
N2O

Answer 11

NO = combustion (engines), thunderstorms, denitrifying bacteria in soi
NO2 = oxidation of NO in atmosphere
N2O = denitrifying bacteria in soil