Question

The ratio of the mass of a certain volume of gas to the mass of an equal volume of hydrogen under the same conditions of temperature and pressure

Answer 1

To solve this question, we need to first understand how the volumes and masses of gases are measured. Following which, we can discuss the property of the gas under consideration.

Complete Step-by-Step Answer:
Before we move forward with the solution of the given question, let us first understand some important basic concepts.
In an experimental setup, we can measure the volume of a gas by measuring the volume of the container that the gas is stored in. But in the case of measuring the mass of a gas we need to use a slightly different method. We can employ a tool known as a ball – in – flowmeter. This tool can be identified as a mass flow meter. What happens in this instrument is basically that the gas will be made to slow through the vertical tube of the mass flow meter. This tube is slightly tapered at the bottom and is broader at the top. There is a little steel ball placed in the tube which gets pushed upwards when the gas is flowing through the tube. The tube is calibrated in the unit’s grams/second. Hence, by measuring the flow and recording the time, we derive the total mass of the gas that was made to flow through the tube.
Now, when we find the ratio of the mass of a certain volume of gas to the mass of an equal volume of hydrogen under the same conditions of temperature and pressure, we get a relation known as vapour density. This quantity can be mathematically represented as:
$Vapour\,density = \dfrac{{weight\,of\,a\,certain\,volume\,of\,gas}}{{weight\,of\,an\,equal\,volume\,of\,{H_2}}}$

Note: If a particular gas has the vapour density value which is less than that gas will generally rise in air. On the other hand, if a gas has a vapour density value which is less than one, then it would generally ink in air