What is the oxidation number for each atom in NH₄F? N=+3, H=-4, F=+1 N=-3, H=+1, F=-1 N=+3, H+1, F=-1 N=-3, H=-1, F=+1?

2016-05-16 4:34 pm

6. What is the oxidation number for each atom in NH₄F?
N=+3, H=-4, F=+1
N=-3, H=+1, F=-1
N=+3, H+1, F=-1
N=-3, H=-1, F=+1
7. Which atom has a change in oxidation number of –3 in the following redox reaction? K₂Cr₂O₇ + H₂O + S → KOH + Cr₂O₃ + SO₂
K
Cr
O
S
9. In a zinc-copper cell, Zn(s) | Zn⁺²(aq) || Cu⁺²(aq) | Cu(s), which electrode is negative?
Cu⁺²
Cu(s)
Zn(s)
Zn⁺²

回答 (1)

胡雪8°

2016-05-16 7:26 pm

✔ 最佳答案

6.
NH₄F contains NH₄⁺ and F⁻.

In NH₄⁺, the sum of oxidation numbers is equal to the charge of ion, i.e. +1.
As the general oxidation number of H = +1,
the oxidation number of N = +1 - 4(+1) = -3

In F⁻, the oxidation number of F is equal to the charge of ion, i.e. -1

..... The answer is : N = -3, H = +1, F = -1

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7.
+ H₂O + S → KOH + Cr₂O₃ + SO₂

Oxidation number of Cr in K₂Cr₂O₇ = +6
Oxidation number of Cr in Cr₂O₃ = +3
Change of oxidation number of Cr = (+3) - (+6) = -3

...... The answer is : Cr

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9.
Zinc is more reactive that copper. Therefore, in a zinc-copper cell, electrons flow from zinc to copper in the external circuit.
As electrons flows from negative electrode to positive electrode, zinc is the negative electrode, and copper is the positive electrode.

...... The answer is : Zn

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