Question

Cisplatin, an anticancer drug, has the molecular formula $Pt{(N{H_3})_2}C{l_2}$. What is the mass (in gram) of one molecule?
(Atomic masses: $Pt = 195,H = 1.0,N = 14,Cl = 35.5$ )
A.$4.98 \times {10^{ - 21}}$
B.$4.98 \times {10^{ - 22}}$
C.$6.55 \times {10^{ - 21}}$
D.$3.85 \times {10^{ - 22}}$

Answer 1

For solving this question we need to know about mole concept. Molar mass is the mass of one mole of that particular molecule. One mole of a compound contains a number of molecules equal to the Avogadro number.

Complete answer:
In cisplatin there is one atom of platinum, three molecules of ammonia and two atoms of Chlorine. Cisplatin is a coordination compound. Cisplatin has a square planar geometry. It gets the prefix cis because it is cis isomer in which two same ligands are attached to the central metal atom (platinum) at the adjacent position. The chemical name of the Cisplatin is cis-diamminedichloroplatinum. In the name we can notice ammine with two m’s this is to indicate that ammonia acts as a ligand here.
For calculating the molar mass of the cisplatin, we will multiply number of each atom with their respective atomic mass and add them.
$M = 195 + (2 \times 14) + (6 \times 1.0) + (2 \times 35.5)$
We get the molar mass of Cisplatin
$\Rightarrow$ $M = 300g/mol$
Now for calculating the mass of one molecule we will divide the molar mass of cisplatin with Avogadro number as one mole of a molecule contains number of molecules equal to the Avogadro number.
Avogadro number: $6.022 \times {10^{23}}mo{l^{ - 1}}$
Mass of one molecule,
$\Rightarrow$ $m = \dfrac{{300}}{{6.022 \times {{10}^{23}}}}$
on simplifying the equation, we get the answer
$\Rightarrow$ $m = 4.98 \times {10^{ - 22}}g$
Hence, the correct answer is option (B).

Note:
Remember the units of each entity and also pay attention to the powers as it can create confusion during calculation. Cisplatin is a medicine that is used to treat a number of cancers some of them are lung cancer, head cancer, neck cancer, breast cancer.