Question #06291

1 Answer
May 5, 2017

Answer:

Here's the balanced equation for the first question:

#"2I"^"-" + "NiO"_2 + 2"H"_2"O"→ "I"_2 + "Ni(OH)"_2 + 2"OH"^"-"#

Explanation:

You can find the detailed procedure here.

The skeleton equation is

#"I"^"-" + "NiO"_2 → "I"_2 +"Ni(OH)"_2#

1. Half-reactions

#"I"^"-" → "I"_2#
#"NIO"_2 → "Ni(OH)"_2#

2. Balance all atoms other than #"H"# and #"O"#

#color(red)(2)"I"^"-" → color(red)(1)"I"_2#
#color(blue)(1)"NiO"_2 → color(blue)(1)"Ni(OH)"_2#

3. Balance O

Done.

4. Balance #"H"#

#color(red)(2)"I"^"-" → color(red)(1)"I"_2#
#color(blue)(1)"NiO"_2 +color(olive)(2)"H"^"+" → color(blue)(1)"Ni(OH)"_2#

5. Balance electrons

#color(red)(2)"I"^"-" → color(red)(1)"I"_2 + color(orange)(2)"e"^"-"#
#color(blue)(1)"NiO"_2 +color(olive)(2)"H"^"+" + color(orange)(2)"e"^"-" → color(blue)(1)"Ni(OH)"_2#

6. Equalize electrons transferred

#1 × [color(red)(2)"I"^"-" → color(red)(1)"I"_2 + color(orange)(2)"e"^"-"]#
#1 × [color(blue)(1)"NiO"_2 +color(olive)(2)"H"^"+" + color(orange)(2)"e"^"-" → color(blue)(1)"Ni(OH)"_2]#

7. Add the two half-reactions

#1 × [color(red)(2)"I"^"-" → color(red)(1)"I"_2 + color(red)(cancel(color(black)(color(orange)(2)"e"^"-")))]#
#1 × [color(blue)(1)"NiO"_2 +color(olive)(2)"H"^"+" + color(red)(cancel(color(black)(color(orange)(2)"e"^"-"))) → color(blue)(1)"Ni(OH)"_2]#
#stackrel(——————————————————)(color(red)(2)"I"^"-" + color(blue)(1)"NiO"_2 + color(olive)(2)"H"^"+" → color(red)(1)"I"_2 + color(blue)(1)"Ni(OH)"_2)#

8. Convert to base

#color(red)(2)"I"^"-" + color(blue)(1)"NiO"_2 + color(red)(cancel(color(black)(color(olive)(2)"H"^"+"))) → color(red)(1)"I"_2 + color(blue)(1)"Ni(OH)"_2#
#2"H"_2"O" →color(red)(cancel(color(black)(2"H"^"+"))) + 2"OH"^"-"#
#stackrel(————————————————————)(color(red)(2)"I"^"-" + color(blue)(1)"NiO"_2 + 2"H"_2"O"→ color(red)(1)"I"_2 + color(blue)(1)"Ni(OH)"_2 + 2"OH"^"-")#

The balanced equation is

#"2I"^"-" + "NiO"_2 + 2"H"_2"O"→ "I"_2 + "Ni(OH)"_2 + 2"OH"^"-"#

Now, can you use the same method to balance the second equation?