Question

The ratio of weights of hydrogen and helium is 1:2. Find the ratio of number of gram atoms.
a) 2:1
b) 1:1
c) 1:4
d) 4:1​

Answer 1

Answer:

answer (b) ,1:1

Explanation:

answer b I think

Answer 2

Given,

Ratio of weights of hydrogen and helium = 1:2

According to the formula of gram molecular mass

Number of gram atoms(N) = Weight in grams(w) / Molecular mass(M)

For hydrogen;

Let the Number of gram atoms be denoted by $N_{H}$

Weight = $W_{H}$

Molecular mass = $M_{H}$ = 1

∴ $N_{H} = \frac{W_H}{M_H}$      (Equation 1)

For helium;

Number of gram atoms = $N_{He}$

Weight = $W_{He}$

Molecular mass = $M_{He}$ = 4

∴$N _{He} = \frac{W_{He}}{M_{He}}$     (Equation 2)

Dividing equation 1 by equation 2 we get

$\frac{N_H}{N_{He}} = \frac{W_H}{W_{He}}$ ×$\frac{M_{He}}{M_H}$

Now according to the question it is given

$\frac{W_H}{W_{He}} = 1:2 = \frac{1}{2}$

and $\frac{M_{He}}{M_H} = \frac{4}{1}$

∴ $\frac{N_H}{N_{He}} = \frac{4}{2} =\frac{2}{1} = 2:1$

Hence the ratio of number of gram atoms is 2:1