Question

v) গ্যাসের বাষ্প ঘনত্ব (D) ও আণবিক ভর (M) এর সম্পর্ক-
2D
a) M = 2D (b) D
= 2M (c) M =
d
১
(d) D=-​

Answer 1

Explanation:

একটি শংকুতে থাকা শীর্ষবিন্দুর সংখ্যা

Answer 2

The relation between vapour density (D) and molecular weight (M) is option (a) M = 2D.

To understand this question, first, we need to learn what is vapour density and molecular weight.

Vapour Density: "Vapour density is the ratio of the mass of a volume of a gas, to the mass of an equal volume of hydrogen, measured under the same conditions of temperature and pressure."

$V.D.=\frac{Mass\ of\ 'X'\ volume\ of\ gas}{Mass\ of\ same\ volume\ of\ Hydrogen}$

Molecular Mass: "Relative molecular mass is the ratio of the mass of one molecule of a substance to the mass of 1 atom of hydrogen or 1 amu."

$Molecular Mass= \frac{Mass\ of\ one\ molecule\ of\ a\ substance}{Mass\ of\ one\ atom\ of\ Hydrogen}$

According to Avogadro's law, "equal volumes of all gases contain an equal number of molecules."

Thus, let the number of molecules in one volume = n,

$V.D.(STP)=\frac{Mass\ of\ n\ molecules\ of\ gas\ or\ vapour\ at\ STP}{Mass\ of\ n\ molecules\ of\ Hydrogen}$

Cancelling the common term "n",

$V.D.(STP)=\frac{Mass\ of\ 1\ molecule\ of\ gas\ or\ vapour\ at\ STP}{Mass\ of\ 1\ molecule\ of\ Hydrogen}$

since hydrogen is diatomic.

$V.D.(STP)=\frac{Mass\ of\ 1\ molecule\ of\ gas\ or\ vapour\ at\ STP}{Mass\ of\ 2\ atoms\ of\ Hydrogen}$

Now, Molecular mass is given by, $Molecular Mass= \frac{Mass\ of\ one\ molecule\ of\ a\ substance}{Mass\ of\ one\ atom\ of\ Hydrogen}$

Therfore, D (Vapour Density) = $\frac{M}{2}$

Hence, M = 2D.