Question

2. Mass of 112 mL of a certain gas is 0.22 g at STP. How many molecules are there in the sample of gas ? What is the molar mass of the gas ?​

Answer 1

Answer:

➜ number of molecules = 30.11 × 10²¹ molecules

➜ molar mass of the gas = 44 g

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Explanation:

\begin{gathered} \\ \\ \end{gathered}

Given,

mass of the given gas, m = 0.22 g

volume of the given gas, V = 112 ml or 0.112 L

\begin{gathered} \\ \\ \end{gathered}

To Find,

☛ number of molecules of the given gas present

☛ molar mass of the gas

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Solution,

\begin{gathered} \\ \end{gathered}

We know,

\begin{gathered} \\ \boxed{ \sf Number \: of \: moles = \frac{volume \: (in \: litres)}{volume \: of \: gas \: at \: S.T.P(22.4)} } \\ \end{gathered}Numberofmoles=volumeofgasatS.T.P(22.4)volume(inlitres)

On substituting the values, we get

→M=22.40.112→M=0.005mol

Now,

1 mol = 6.022 × 10²⁴ atoms / molecules

0.005 mol = 6.022 × 0.005 × 10²⁴

➜ 6.022 × 5 × 10²¹

➜ 30.11 × 10²¹ molecules

Also,

No. of moles = Mass given / Molar mass

☛ 0.005 = 0.22 / molar mass

☛ molar mass = 0.22 / 0.005

☛ molar mass = 44 g