Clarity Silicone
Can you answer these Chemistry questions with good clarity and explanation?
1) Explain why carbon dioxide is a gas at room temperature and pressure, whereas silicon dioxide is a solid with a very high melting temperature.
2)Explain why hydrogen iodide has a higher boiling temperature than hydrogen chloride.
3)Explain why sodium chloride conducts electricity when molten but not when solid.
4)Silicon and phosphorus are both covalent substances, but silicon has a much higher melting temperature than phosphorus.
1. SiO2 exists as a gigantic molecular structure while CO2 contains C bonded to 2 O via double bond. SiO2 can't form double bond with O due to its orbitals nature (Si uses its d orbital for bonding). CO2 structure (O=C=O) is discrete and that's why it exists as gas at room T and P. It's anomalous as Si theoretically should have lower melting point than C in periodic table.
2. When it comes to boiling point determination, molecular weight plays a huge role. You see, down the group in the halogens' group, size of atom increases. Chlorine is above iodine in the group. Iodine has bigger molecular weight. When they form a compound with same cation, like HCl and HI, HI will give higher boiling point value than HCl's
3. In solid NaCl, ions (Na+ and Cl-) are immobile and at the lattice only. They can't move and in fact, they just vibrate. So, in order to conduct electricity, ions must be free. That's why molten NaCl can conduct electricity while solid NaCl can't. Ions are free to move in molten state.
4. As in 1, Si has gigantic structure due to its orbital nature which is used for bonding. Higher energy needed to break the covalent bonds.
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