Question

The mass in grams of a single chlorine atom and of single molecule of ${O_2}$ is:
A.5.89$ \times $ ${10^{ - 23}}$ g/atom , 5.31 $ \times $ ${10^{ - 23}}$ g/atom
B.8.81$ \times $ ${10^{ - 23}}$ g/atom, 4.31$ \times $ ${10^{ - 23}}$ g/atom
C.5.81$ \times $ ${10^{ - 25}}$ g/atom, 5.31$ \times $ ${10^{ - 25}}$ g/atom
D.None of the above

Answer 1

Hint: Molecular mass or atomic mass of atom or molecule is equal to the mass of that compound in 1 mole of molecules or mass of $6.022 \times {10^{23}}$ molecules. To solve such a question we need to find out the number of moles of the substance.

Complete Step by step answer: Atomic Mass of chlorine, $Cl$ = 35.5 gm
That is $6.022 \times {10^{23}}$ atoms of $Cl$ have mass= 35.5 gram
So by dividing mass of chlorine atom by avogadro number we get one atom of $Cl$ contains mass= 5.89$ \times $ ${10^{ - 23}}$ g/atom
Molecular mass of oxygen is ${O_2}$= (16)2 = 32 gram
That is $6.022 \times {10^{23}}$molecules of ${O_2}$have mass= 32 gram
So one molecule of ${O_2}$ have mass = 5.31 $ \times $ ${10^{ - 23}}$g/atom
Therefore, the mass in grams of a single chlorine atom and of single molecule of ${O_2}$ are 5.89$ \times $ ${10^{ - 23}}$ g/atom and 5.31 $ \times $ ${10^{ - 23}}$ g/atom.

So the correct option for this question is A.

Note: Molecular mass can be found by adding the atomic masses (found in the periodic table usually in the bottom left of the element although some outliers mean that it is usually worth just using the bigger number written) of all the components.