How to determine which molecule has the highest melting point?

In summary, the substance with the highest melting point among the given options is SiO2, also known as sand. While there is no guaranteed method for determining melting points, the fact that CO and CO2 are gases at STP and the difficulty of melting sand suggest that SiO2 has the highest melting point.
  • #1
gsingh2011
115
1
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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  • #2
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.
 

Related to How to determine which molecule has the highest melting point?

1. How do I compare melting points of different molecules?

To compare melting points of different molecules, you need to determine the intermolecular forces present in each molecule. Molecules with stronger intermolecular forces will have higher melting points.

2. What are the factors that affect a molecule's melting point?

The factors that affect a molecule's melting point include molecular weight, size and shape of the molecule, polarity, and strength of intermolecular forces.

3. Can the melting point of a molecule be predicted?

Yes, the melting point of a molecule can be predicted by analyzing its structure and determining the intermolecular forces present. However, experimental data is still needed to confirm the predicted melting point.

4. How does the molecular structure affect the melting point?

The molecular structure affects the melting point by determining the strength of intermolecular forces. For example, molecules with more compact and symmetrical structures tend to have stronger intermolecular forces and higher melting points.

5. Is there a relationship between boiling point and melting point?

Yes, there is a relationship between boiling point and melting point. Generally, molecules with higher melting points also have higher boiling points due to the stronger intermolecular forces present.

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