Chemistry Class 12 NCERT Solutions: Chapter 1 The Solid State Part 8

Q: 15. Copper crystallises into a fcc lattice with edge length Equation . Show that the calculated density is in agreement with its measured value of Equation .

Ans:

Edge length, Equation

As the lattice is fcc type, the number of atoms per unit cell, Equation

Atomic mass, Equation

We also know that, Equation

Applying the relation:

Equation

Equation

Equation

The measured value of density is given as Equation . Hence, the calculated density Equation is in agreement with its measured value.

Q: 16. Analysis shows that nickel oxide has the formula Equation . What fractions of nickel exist as Equation ions?

Ans:

The formula of nickel oxide is Equation .

Therefore, the ratio of the number of Ni atoms to the number of O atoms Equation

Now , total charge on Equation

Equation

Let the number of Equation is Equation .

Now, total charge on Equation

Equation

And, total charge on Equation

Equation

Since, the compound is neutral, we can write:

Equation

Equation

Equation

Therefore, number of Equation ions Equation

And, number of Equation ions Equation

Hence, fraction of nickel that exists as Equation

Equation

And, fraction of nickel that exists as Equation

Equation

Alternatively, fraction of nickel that exists as Equation

Equation

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