# (a) Following is the alignment of magnetic moments of a substance when placed in a magnetic field. Identify the type of magnetism exhibited by the substance.(b) Analysis shows that nickel oxide has formula $Ni_{0.98}O_{1.00}$. What frctions of nickel exist as $Ni^{2+}$ and $Ni^{3+}$ ions?

(a) Since all the magnetic moments are directed in the same direction, the substance exhibit ferromagntism.

(b) Ratio of Ni and O in Nickel oxide is,

$\frac{Ni}{O}= \frac{0.98}{1.00}=\frac{98}{100}$

Total nickel atoms for 100 atoms of oxygen is 98.

Let x be the number of nickel with +2 charge.

$\therefore$ Nickel with +3 charge = 98 - x

charge of nickel = charge on oxygen

$\therefore$ $2\times x + (+3)(98-x)= 2\times 100$

$2 x +294-3x= 200$

$-x = 200 - 294= -94$

$x = 94$

$\therefore$ Nickel with +2 charge = $\frac{94}{98}=96$%

$\therefore$ Nickel with +3 charge = $98-94=4 out of 98 =\frac{4}{98}=4$%

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