you need
  • - Periodic Table of Elements DIMendeleev
  • - Calculator.
Guide
1
To cope with the task, you must use a formula to determine the relative den
sity:

D (air) = Mr (gas) / Mr (air) where:

D(air) - the relative density;
Mr (gas) - relative molecular mass of the gaseous substance;
Mr (Air) - relative molecular mass of air.

All three units of the parameter no.

Mr (air) = 29 (a constant value), so the formula is of the form:
D (air) = Mr (gas) / 29.
2
By analogy seems a formula to determine the relative densityhydrogen, with the exception that instead of air necessary hydrogen.And that means that in the calculation of a relative molecular mass of hydrogen.

D (hydrogen) = Mr (gas) / Mr (hydrogen);
D (hydrogen) - relative density;
Mr (gas) - relative molecular mass of the gaseous substance;
Mr (hydrogen) - relative molecular mass of hydrogen.

Mr (hydrogen) = 2, and thus the formula will look like:
D (air) = Mr (gas) / 2.
3
Example № 1. Calculate the relative density of ammonia in the air.Ammonia has the formula NH3.

First find the relative molecular mass of ammonia, which can be calculated from Table D.Mendeleev.

Ar (N) = 14, Ar (H) = 3 x 1 = 3, hence
Mr (NH3) = 14 + 3 = 17

Put data into a formula for determining the relative density of the air:
D (air) = Mr (ammonia) / Mr (air);
D (air) = Mr (ammonia) / 29;
D (air) = 17/29 = 0, 59.
4
Example № 2. Calculate the relative density of ammonia to hydrogen.

Substitute the data in a formula to determine the relative density of hydrogen:
D (hydrogen) = Mr (ammonia) / Mr (hydrogen);
D (hydrogen) = Mr (ammonia) / 2;
D (hydrogen) = 17/2 = 8, 5.