There are two binary compounds of mercury and oxygen. heating either of them results in the decomposition of the compound, with oxygen gas escaping into the atmosphere while leaving a residue of pure mercury. heating 0.6498 g of one of the compounds leaves a residue of 0.6018 g. heating 0.4172 g of the other compound results in a mass loss of 0.016 g. determine the empirical formula of each compound.

Respuesta :

[tex] \text{Hg} \text{O} [/tex] and [tex] \text{Hg}_{2} \text{O} [/tex].

Assuming complete decomposition of both samples,

  • [tex] m(\text{Hg}) = m(\text{residure}) [/tex]
  • [tex] m(\text{O}) = m(\text{loss}) [/tex]

First compound:

  • [tex] m(\text{O}) = m(\text{loss}) = 0.6498 - 0.6018 = 0.048 \; g [/tex]
  • [tex] m(\text{Hg}) = m(\text{residure}) = 0.6018 \; g [/tex]

[tex] n = m/M [/tex]; [tex] 0.6498 \; g [/tex] of the first compound would contain

  • [tex] n(\text{O atoms}) = 0.048 \; g / 16 \; g \cdot mol^{-1}= 0.003 \; mol [/tex]
  • [tex] n(\text{Hg atoms}) = 0.6018 \; g / 200.58 \; g \cdot mol^{-1}= 0.003 \; mol [/tex]

Oxygen and mercury atoms seemingly exist in the first compound at a [tex] 1:1 [/tex] ratio; thus the empirical formula for this compound would be [tex] \text{Hg} \text{O} [/tex] where the subscript "1" is omitted.

Similarly, for the second compound

  • [tex] m(\text{O}) = m(\text{loss}) = 0.016 \; g [/tex]
  • [tex] m(\text{Hg}) = m(\text{residure}) = 0.4172 - 0.016 = 0.4012 \; g [/tex]

[tex] n = m/M [/tex]; [tex] 0.4172 \; g [/tex] of the first compound would contain

  • [tex] n(\text{O atoms}) = 0.016 \; g / 16 \; g \cdot mol^{-1}= 0.001 \; mol [/tex]
  • [tex] n(\text{Hg atoms}) = 0.4012 \; g / 200.58 \; g \cdot mol^{-1}= 0.002 \; mol [/tex]

[tex] n(\text{Hg}) : n(\text{O}) \approx 2:1 [/tex] and therefore the empirical formula

[tex] \text{Hg}_{2} \text{O} [/tex].