With RRMS, the patient experiences relapses (attacks, exacerbations, or flare-ups) during which there are increased symptoms and/or a worsening of neurologic function, followed by partial or complete recovery (or remission). Much more common: RRMS is much more common than progressive courses of MS, which only affect 10% to 15% of patients.
Vapor density is the density of a vapour in relation to that of hydrogen.It may be defined as mass of a certain volume of a substance divided by mass of same volume of hydrogen. vapor density = mass of n molecules of gas / mass of n molecules of hydrogen.Therefore:vapour density = molar mass of gas / molar mass of H 2.or example, acetone has a vapour density of 2 in relation to air. That means acetone vapour is twice as heavy as air. This can be seen by dividing the molecular weight of Acetone, 58.1 by that of air, 28.97, which equals 2.
If you know the density of a gas at a particular temperature and pressure, it is very easy to work out its molar volume. For example, at 273 K and 1 atmosphere pressure, the density of helium is 0.1785 g dm -3. That means that 0.1785 g of helium occupies 1 dm 3 at stp.