What is the oxidation number of mn in ca(mno4)2

+ 7.

Explanation:

We have general rules to assign the oxidation numbers:

Rule 1: The oxidation number of an element alone in its free (uncombined) state is zero.

For example, Al(s) or Zn(s).

This is also true for elements found in nature as diatomic (two-atom) elements  as: H₂, O₂, Cl₂, or I₂.

and also for sulfur, found as: S₈.

Rule 2: The oxidation number of a monatomic (one-atom) ion is the same as the charge on the ion,

For example:  Na⁺ = +1, S⁻² = -2.

Rule 3: The sum of all oxidation numbers in a neutral compound is zero. The sum of all oxidation numbers in a polyatomic (many-atom) ion is equal to the charge on the ion.

Rule 4: The oxidation number of an alkali metal (group IA) in a compound is +1; the oxidation number of an alkaline earth metal (group IIA) in a compound is +2.

Rule 5: The oxidation number of oxygen in a compound is usually –2.

If, however, the oxygen is in a class of compounds called peroxides.

(for example, hydrogen peroxide), then the oxygen has an oxidation number of –1. If the oxygen is bonded to fluorine, the number is +1.

So, for our problem Ca(MnO₄)₂:

∴ oxidation no. of Ca + 2[(oxidation no. of Mn) + 4(oxidation no. of O) = 0.

(+2) + 2[(oxidation no. of Mn) + (- 8)] = 0.

2[(oxidation no. of Mn) + (- 8)] = - 2.

[(oxidation no. of Mn) + (- 8)] = -1.

∴ (oxidation no. of Mn) = - 1 + 8 = + 7.

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.

20 drops hope this