Chemistry 5070 · O Level · Diffusion

Diffusion — practice question

Information on two compounds is shown below. Both compounds have simple molecular structures. Compound data: - $\text{H}_2\text{S}$: melting point $-85\,^{\circ}\text{C}$, boiling point $-61\,^{\circ}\text{C}$ - $\text{PCl}_3$: melting point $-112\,^{\circ}\text{C}$, boiling point $76\,^{\circ}\text{C}$ Two bottles are positioned close to each other inside a large container kept at $90\,^{\circ}\text{C}$. One bottle holds $1.0\,\text{g}$ of $\text{H}_2\text{S}$, and the other holds $1.0\,\text{g}$ of $\text{PCl}_3$. A detector is located in the container $2.0\,\text{m}$ from the two bottles. The bottles are opened simultaneously. Which row gives the correct answer?

  • A$\text{H}_2\text{S}$; gases diffuse faster than liquids
  • B$\text{H}_2\text{S}$; $\text{H}_2\text{S}$ has a lower $M_r$ than $\text{PCl}_3$
  • C$\text{PCl}_3$; gases diffuse faster than liquids
  • D$\text{PCl}_3$; $\text{PCl}_3$ has a lower $M_r$ than $\text{H}_2\text{S}$

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