0.79g of a gas as s.t.p occupied a volume of 250cm 3 . What is...
0.79g of a gas as s.t.p occupied a volume of 250cm3. What is the relative molecular mass of the gas? [G.M.V. at s.t.p = 22.4dm3]
- A) 17
- B) 32
- C) 64
- D) 71
Correct Answer: D) 71
Explanation
To calculate the relative molecular mass of the gas, we first need to determine the number of moles of the gas. We can do this using the given mass of the gas and the molar volume of the gas at standard temperature and pressure (s.t.p).
At s.t.p, one mole of any gas occupies a volume of 22.4 dm\(^3\), which is equivalent to 22,400 cm\(^3\). Now, we can find the number of moles (n) of the gas using the following formula:
\[n = \frac{Volume\, of\, Gas}{Molar\, Volume\, at\, s.t.p}\]
Substituting the given values, we get:
\[n = \frac{250\, cm^3}{22,400\, cm^3}\]
This simplifies to:
\[n = 0.01116\, mol\]
Now, to find the relative molecular mass (M) of the gas, we can use the formula:
\[M = \frac{Mass\, of\, Gas}{Number\, of\, Moles}\]
Substituting the given values, we get:
\[M = \frac{0.79\, g}{0.01116\, mol}\]
This simplifies to:
\[M \approx 71\]
Therefore, the relative molecular mass of the gas is approximately 71, which corresponds toOption D.