Such characteristic as relative density of substance, shows how much it is heavier or lighter than other connection. This parameter can be determined in relation to any gaseous substance. Calculations concerning air or hydrogen are in most cases carried out. However tasks in which it is necessary to calculate relative density and on other gases, such as oxygen, ammonia or hydrogen sulfide can come across. Anyway the principle of the solution of a task is uniform.
It is required to you
- - Periodic Table of D.I. Mendeleyev;
- - calculator.
Instruction
1. To cope with a task, it is necessary to use formulas on determination of relative density: D (air) = Mr (gas) / Mr (air), where: D (air) – relative density; Mr (gas) there is a relative molecular mass of gaseous substance; Mr (air) there is a relative molecular mass of air. All three parameters of units of measure have no. Mr (air) = 29 (constant), therefore the formula will have an appearance: D (air) = Mr (gas) / 29.
2. By analogy the formula on determination of relative density on hydrogen, with that exception looks that instead of air there is a hydrogen. So, and the relative molecular mass of hydrogen.D (hydrogen) = by Mr (gas) / Mr (hydrogen) is taken into account; D (hydrogen) – relative density; Mr (gas) there is a relative molecular mass of gaseous substance; Mr (hydrogen) there is a relative molecular mass of hydrogen.Mr (hydrogen) = 2, therefore and the formula will have an appearance: D (air) = Mr (gas) / 2.
3. Example No. 1. Calculate the relative density of ammonia by air. Ammonia has NH3 formula. At first find the relative molecular mass of ammonia which can be calculated according to D.I. Mendeleyev's table. Ar (N) = 14, Ar (H) = 3 x 1 = 3, from here Mr (NH3) = 14 + 3 = 17podstavte the obtained data in a formula on determination of relative density by air: D (air) = Mr (ammonia) / Mr (air); D (air) = Mr (ammonia) / 29; D (air) = 17/29 = 0, 59.
4. Example No. 2. Calculate the relative density of ammonia on hydrogen. Substitute data in a formula on determination of relative density on hydrogen: D (hydrogen) = Mr (ammonia) / Mr (hydrogen); D (hydrogen) = Mr (ammonia) / 2; D (hydrogen) = 17/2 = 8, 5.