How to determine which molecule has the highest melting point?

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SUMMARY

The highest melting point among the substances CO, CO2, SiO2, and P2O5 is SiO2. The reasoning is based on the physical states of the substances at standard temperature and pressure (STP), where CO and CO2 are gases, eliminating them from consideration. The remaining candidates, P2O5 and SiO2, lead to the conclusion that SiO2, commonly known as sand, has a significantly higher melting point due to its strong covalent bonding structure.

PREREQUISITES
  • Understanding of molecular states at standard temperature and pressure (STP)
  • Knowledge of covalent bonding and its impact on melting points
  • Familiarity with common substances and their physical properties
  • Basic chemistry concepts regarding phase changes
NEXT STEPS
  • Research the melting points of SiO2 and P2O5 for comparative analysis
  • Study the properties of covalent compounds and their melting behaviors
  • Explore the phase diagrams of various substances to understand state changes
  • Learn about the factors influencing melting points in different molecular structures
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Chemistry students, educators, and professionals interested in material properties and phase transitions will benefit from this discussion.

gsingh2011
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The question is: Which substance has the highest melting point?
(A) CO (B) CO2 (C) SiO2 (D) P2O5

The answer is C but I don't know why (you obviously can't look up the values). I need to be able to figure these types of questions out regardless of the molecules given in the choices.
 
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For the record: thread title doesn't make sense. Molecules don't have melting points. Substances do.

I am not aware of a bullet proof method for determining melting points. However, first two substances are gases at STP, so they are ruled out, and we are left with P2O5 and SiO2. The latter is just a sand, and sand is pretty difficult to melt, so even not knowing anything about P2O5 I would say that's the answer.
 

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