Question

A sample of Ni(CO)4, a toxic transition-metal complex, has 5.23 x 10^24 atoms of carbon. How many atoms of Ni does it contain?

Answer 1

Answer: The correct answer is Option E.

Explanation:

We are given a chemical compound having formula $Ni(CO)_4$

In 1 mole of the compound, 1 mole of nickel atom, 4 moles of carbon atom and 4 moles of oxygen atom are present.

According to mole concept:

1 mole of a substance contains $6.022\time 10^{23}$ number of particles

Number of carbon atoms in compound = $4\times 6.022\times 10^{23}$

Number of nickel atoms in compound = $1\times 6.022\times 10^{23}$

We are given:

Number of carbon atoms = $5.23\times 10^{24}$

To calculate the number of nickel atoms for given amount of carbon atom, we use unitary method:

When $4\times 6.022\times 10^{23}$ number of carbon atoms are present, then $6.022\times 10^{23}$ number of nickel atoms are also present.

So, when $5.23\times 10^{24}$ number of carbon atoms are present, then $\frac{4\times 6.022\times 10^{23}}{6.022\times 10^{23}}\times 5.23\times 10^{24}=1.31\times 10^{24}$ number of nickel atoms are also present.

Hence, the correct answer is Option E.

Answer 2

In Ni(CO)₄ the stoichiometry of Ni to C is 1:4
for every 4 atoms of C is attached to one Ni atom.
this means that if there are 4 atoms of C - 1 atom of Ni
in 5.23 x 10²⁴ atoms of C -1/4 x 5.23 x 10²⁴ atoms of Ni
                                        = 1.3075 x 10²⁴ atoms of Ni
the number of atoms rounded off to the second decimal place = 1.31 x 10²⁴ atoms 
correct answer is E