Question

Calculate the number of atoms of carbon (C) in 340. cm3 of the colorless gas methylacetylene at 0 °C and atmospheric pressure, where its density is 1.79×10-3 g cm-3. The molecular formula of methylacetylene is C3H4.

Answer 1

Answer: The number of C-atoms in methylacetylene are
`2.746* 10^(22)`

Step-by-step explanation:

To calculate the number of atoms, we first need to calculate the number of moles. For that we use the equation of ideal gas, which is:

`PV=nRT`

where,

P = pressure of the gas = 1 atm

V = Volume of the gas =
`340cm^3=0.34L` (Conversion Factor:
`1cm^3=0.001L` )

n = Number of moles = ?

R = gas constant =
`0.08205\text{ L atm }mol^(-1)K^(-1)`

T = temperature of the gas =
`0^oC=273K` (Conversion factor:
`T(K)=T(^oC)+273` )

Putting values in above equation, we get:

`1atm* 0.34L=n* 0.08205\text{ L atm }mol^(-1)K^(-1)* 273K\\\\n=0.0152mol`

According to the mole concept:

1 mole of a compound contains
`6.022* 10^(23)` number of atoms

As, 1 mole of methylacetylene contains
`3* 6.022* 10^(23)` number of C-atoms.

So, 0.0152 moles of methylacetylene contains
`0.0152* 3* 6.022* 10^(23)=2.746* 10^(22)` number of C-atoms.

Hence, the number of C-atoms in methylacetylene are
`2.746* 10^(22)`