Balance each of the following equations according to the half- reaction method:
(a) zn + no3- --> zn2+ + n2 (in acid)
(b) zn + no3- --> zn2+ + nh3 (in base)
(c) cus + no3- --> cu2+ + s + no (in acid)
(d) nh3 + o2 --> no2 (gas phase)
(e) cl2 + oh- --> cl- + clo3-(in base)
(f) h2o2 + mno4- --> mn2+ o2 (in acid)
(g) no2 --> no3- + no2- (in base)
(h) fe3+ + i- --> fe2+ +i2

a) 12H+ + 6Zn + 2NO3 → 6Zn2+ + N2 + 6H2O

b) 12H2O + 9Zn + 2NO3 → 9Zn2+ + 2NH3 + 18OH-

c) 4H+ + 2CuS + NO3  → 2Cu2+ + 2S + NO + 2H2O

d) 7O2 + 4NH3 → 4NO2 + 6H2O

e) 13Cl2 + 26OH- + 10OH +  → 6ClO3- + 18H2O + 20Cl-

f) 5H2O2 + 2MnO4- + 6H+ → 5O2 + 2Mn2+ + 8H2O

g) 2NO2 + 2OH- → NO3- + NO2- + H2O

h) 2I- + 2Fe3+ → I2 + 2Fe2+

Explanation:

a) oxidation states :

⇒ Zn: 0 → 2+ : lose 2e-

⇒ N : +6 → 0 : win 6e-

half reaction:

⇒ ( 1 ) Zn → Zn2+ + 2e-

⇒ ( 2 ) 2NO3 + 12H+ 12e- → N2 + 6H2OThe O are balanced with H2O and the H with H +, then balanced the charges with e-.

( 1 ) * 6:

⇒ ( 7 ) 6Zn → 6Zn2+  +  12e-

( 7 ) + ( 2 ):

⇒ 12H+ + 6Zn + 2NO3 → 6Zn2+ + N2 + 6H2O

                  6 - Zn - 6

                  2 - N - 2

                  6 - O - 6

                  12 - H - 12

b) oxidation states:

⇒ Zn: 0 → 2+ ≡ 2e-

⇒ N: +3 → -3 ≡ 6e-

half reaction:

( 1 ) Zn → Zn2+ + 2e-

(2 ) 9H2O + 9e- + NO3 → NH3 + 3H2O + 9OH-each H + ion present in the equation is added a respective OH- ion to each side of the equation, and the combination of OH- and H + ions found on the same side of the equation is replaced with a water molecule.

∴ ( 1 ) * 9 and ( 2 ) * 2 and then i add them:

⇒ 18H2O + 9Zn + 2NO3 → 9Zn2+ + 2NH3 + 6H2O + 18OH-

                  9 - Zn - 9

                  2 - N - 2

                  24 - O - 24

                 36 - H - 36

c) oxidation states:

∴ S:  -2 → 0 ≡ 2e-

∴ N: +6 → +2 ≡ 4e-

half reaction:

( 1 ) CuS → Cu2+ + S + 2e-

( 2 ) NO3 + H2O + 4H+  + 4e- → NO + 3H2O

∴( ( 1 ) * 2 ) + ( 2 ):

⇒ 4H+ + 2CuS + NO3  → 2Cu2+ + 2S + NO + 2H2O

                      2 - Cu - 2

                      1 - N - 1

                      2 - S - 2

                      3 - O - 3

                      4 - H - 4

d) oxidation states:

∴ O: 0 → -2 ≡ 2e-

∴ N: -3 → +4 ≡ 7e-

half reaction:

( 1 ) O2 + 4H+ + 4e- → 2H2O

( 2 ) NH3 + 2H2O → NO2 + 7H+  + 7e-

∴  ( 1 ) * 7 and ( 2 ) * 4 and then i add them:

⇒ 7O2 + 4NH3 + 8H2O → 4NO2 + 14H2O

⇒ 7O2 + 4NH3 → 4NO2 + 6H2O

            4 - N - 4

            14 - O - 14

            12 - H - 12

e) oxidation states:

∴ Cl: 0 → -1 ≡ 1e-

∴ Cl: 0 → +5 ≡ 5e-

∴ O: -1 → -2 ≡ 1e-

half reaction:

( 1 ) Cl2 + 6H2O → 2ClO3- + 12H+

( 2 ) Cl2 + OH + H+ → Cl- + H2O

in base:

( 1 ) Cl2 + 6H2O + 12OH- → 2ClO3- + 12H2O

( 2 ) Cl2 + OH + H2O → 2Cl- + H2O + OH-

the charge are balanced:

( 1 ) Cl2 + 6H2O + 12OH- → 2ClO3- + 12H2O + 10e-

( 2 ) Cl2 + OH + H2O + 3e- → 2Cl- + H2O + OH-

∴ ( 1 ) * 3 and ( 2 ) * 10, then i add them:

⇒ 13Cl2 + 26OH- + 10OH +  → 6ClO3- + 18H2O + 20Cl-  

               26 - Cl - 26

               36 - O - 36

                36 - H - 36

f) oxidation states:

∴ O: -1 → 0 ≡ 1e-

∴ O: -2 → 0 ≡ 2e-

∴ Mn: +7 → +2 ≡ 5e-

half reaction:

( 1 ) H2O2 → O2 + 2H+ + 2e-

( 2 ) MnO4- + 8H+ + 5e- → Mn2+ + 4H2O

∴ ( 1 ) * 5 and ( 2 ) * 2, then i add them:

⇒5H2O2 + 2MnO4- + 6H+ → 5O2 + 2Mn2+ + 8H2O

               2 - Mn - 2

               18 - O - 18

               16 - H - 16

g) oxidation states:

∴ N: +4 → +5 ≡ 1e-

∴ N: +4 → +3 ≡ 1e-

half reaction:

( 1 ) NO2 + H2O + 2OH- → NO3- + 2H+

( 2 ) NO2 → NO2-

⇒ ( 1 ) NO2 + H2O + 2OH- →  NO3- + 2H2O + 1e-

⇒ ( 2 ) NO2 + 1e- → NO2-

( 1 ) + ( 2 ):

⇒ 2NO2 + 2OH- → NO3- + NO2- + H2O

                 2 - N - 2

                 6 - O - 6

                 2 - H - 2

h) oxidation states:

∴ Fe: +3 → +2 ≡ 1e-

∴ I: -1 → 0 ≡ 1e-

half reaction:

( 1 ) 2I- → I2 + 2e-

( 2 ) Fe3+ +1e- → Fe2+

∴ (( 2 ) * 2 ) + ( 1 ):

⇒ 2I- + 2Fe3+ → I2 + 2Fe2+

      2- I - 2

      2 - Fe - 2

the atomic number will stay the same no matter how many electrons it has, so it doesn’t decrease nor increase. it’ll only change with a different number of protons

hurricanes form when warm, moist air from the ocean surface quickly rises into the atmosphere and forms storm clouds and rain. when the clouds are formed, heat is released which warms the cool air in the upper regions of the atmosphere so that the cycle can continue. which two phases of the water cycle are repeated in this process?