hydrocarbon is ethene which is used to test for saturation and it undergoes addition reaction
The relative molecular mass of the gas : 64 g/mol
<h3>Further explanation</h3>
Given
Helium rate = 4x an unknown gas
Required
The relative molecular mass of the gas
Solution
Graham's Law

r₁=4 x r₂
r₁ = Helium rate
r₂ = unknown gas rate
M₁= relative molecular mass of Helium = 4 g/mol
M₂ = relative molecular mass of the gas
Input the value :

Answer:
Length = 393pm, Density = 21.3 g/cm^3.
Explanation:
From the question above, we have the following parameters or data which is going to aid in solving the above Question.
=> The radius of a platinum atom = 139 pm.
Therefore, the length can be calculated by making use of the formula given below:
Length = 2 √( 2r) = 2 × √ (2 × 139 × 10^-12m ) = 393 × 10^-10 m = 393pm.
The density can be calculated by making use of the chemical formula given below:
Density = mass ÷ volume = (195.064/ 6.02 × 10^23) ÷ (3.93 × 10^-10/ 10^-2) = 21.3 g/cm^3.