Question

one molecule of a compound contains 6 carbon atoms, 2×10^-23 g of hydrogen and 16×10^-23g of other atoms. the gram molecular mass of this compound is?

Answer 1

The Molecular mass of the compound is 221.079 amu

What is Atomic Mass Unit (AMU) ?

• Since atoms and other subatomic particles are small, we cannot express their mass in grams.
• So we need another smaller unit called Atomic Mass Unit (AMU).
• $1\hspace{ 1 mm}amu= 1.67 * 10^{-24} g$
• Mass of one proton and one neutron is approximately 1 amu.

Given:

Compound contains:

• Number of Carbon atoms = 6
• Mass of Hydrogen atoms = $2*10^{-23} g$
• Mass of other atoms = $16*10^{-23}g$

We can observe,

Mass of 6 Carbon atoms = $6 * 12 = 72 \hspace{1 mm}amu$

(This is because each Carbon atom weighs 12 amu )

Mass of the given Hydrogen atoms = $\frac{2*10^{-23}}{1.67*10^{-24}} = 11.976\hspace{ 1 mm} amu$

Mass of other atoms = $\frac{16*10^{-23}}{1.67*10^{-24}} = 137.103\hspace{ 1 mm} amu$

Therefore,

Molecular mass of the compound $(72 + 11.976 + 137.103) \hspace{ 1 mm} amu = 221.079 \hspace{ 1 mm} amu$

So, The Molecular mass of the compound is 221.079 amu