Question

a flask can hold 1.64 g of hydrogen at stp.
i) calculate the mass of methane it can hold at stp.
ii)the number of molecules of carbon dioxide it can hold at stp.

Answer 1

No. of moles of H₂ = $\frac{1.64}{2}$ =0.82 moles

i) Mass of methane :

Under ideal gas condition no. of moles remain the same.
Therefore,
No. of moles of methane = no. of moles of H₂ = 0.82 moles.

mass of methane = no. of moles of methane * molar mass of methane
= 0.82 $\times$ 16
= 13.12g
ii) No. of moles of carbon dioxide = No. of moles of methane = 0.82 moles
No. of molecules of carbon dioxide $$\begin{gathered} =0.82\times NA \\ =0.82\times 6.022\times 1023 \\ =4.9\times 1023 \end{gathered}$$